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Laser interactions with materials: from fundamentals to applications

This laser symposium aims to bring together leading academic scientists, researchers and laser users and manufacturers to exchange and share their experiences on recent progress in Laser Science and Technology, in particular in the field of laser materials processing and synthesis. It also provides the chance to present and discuss the most recent innovations, trends, and concerns, practical challenges from nanoenergy to biomedicine.


This symposium will cover all new advances in laser-matter interaction coupled to recent applications of emerging materials. The main objective is to revisit the basic phenomena involved in the interaction of wide range of laser systems still new and efficient devices including smart optics, high and low repetition rate processing as well as high and low beam fluences. The symposium will consider recent progress in laser-assisted additive fabrication, nano-LIPSS formation, laser lift of biological materials and systems and more emerging techniques such as laser synthesis of nanoparticles in liquids, and will offer a unique opportunity for researchers from Europe and worldwide areas to discuss their results in a friendly and engaging atmosphere. Laser techniques will facilitate environmental and eco-design through the useful processing of photovoltaic cells, thermoelectricity materials and devices, micro and nanosystems for energy storage and conversion; a special focus will be given for those ‘hot’ topics. All contributions on laser interaction with hard, soft and smart materials, targeting future applications from nanoenergy to biomedicine as well as recent progress on the fundamental mechanisms are welcome. The symposium Laser Interactions with Materials: from fundamentals to applicationswill provide a platform to establish interdisciplinary international research collaborations between scientists working in the field of laser-matter interaction.

The symposium will consist of invited presentations by leading scientists in their respective fields of research and contributed papers for oral and poster presentations. Special emphasis will be made for presentations by young scientists presenting high quality research papers. The contributions should concern, but are not limited to the topics listed below.

Hot topics to be covered by the symposium:

  • Lasers in nanotechnology and environmental technology,
  • Laser hybrid processing,
  • Laser synthesis and processing of colloids
  • Laser manufacturing for alternative energy sources.
  • Laser 3D micro-structuring for MEMS, MOEMS, photonic crystals and photonic applications;
  • Laser Induced Forward Transfer of functional materials for organic electronics and sensing applications;
  • Laser assisted fabrication for sensors (bio-, chemical- and environmental-);
  • Ultra-short, ultra-high power laser interaction with matter: fundamentals and applications in biology and materials science;
  • Laser processing of materials: thin films growth and particle production; Subwavelength laser produced structures for smart optical, electro-optical, electronic and biological devices; Laser-induced nanostructures: from theory to applications;
  • Time-resolved diagnostics for laser processing; Multiphoton based processing techniques.
  • Diode lasers for processing and pumping,
  • Laser process monitoring and control, laser processing of biological materials

List of invited speakers:

  • Alfred Vogel - University of Lübeck (Germany) - keynote in symposium with 45 min
  • Florent Calvo - Université Joseph Fourier (France)
  • Astrid Müller – Caltech (USA)
  • Leonid Zhigilei – Univ. of Virginia (USA)
  • Changhao Liang - Chinese Academy of Sciences (China)
  • David Amans - Institut Lumière Matière (France)
  • Paolo Maria Ossi - Politecnico di Milano (Italy)
  • Guus Rijnders – University of Twente (The Netherlands)
  • M. Cernaianu - Extreme Light Infrastructure, Nuclear Physics (Romania)
  • Guillaume Baffou – Institut Fresnel Marseille (France)
  • V. Venkatesan – University of Singapore (Singapore)

Tentative list of scientific committee members:

V. Amendola – Univ. of Padova (Italy), S. Amoruso - CNR-INFM Napoli (Italy), C.B. Arnold - Princeton University (USA),  C. Boulmer-Leborgne - GREMI Université d'Orléans (France), I.W. Boyd – London Brunel University, N.M. Bulgakova - Institute of Thermophysics SB-RAS (Russia), C. Champeaux - Université de Limoges (France), B. Chichkov, Laser Zentrum Hannover (Germany), F. Costache - Fraunhofer Institute for Photonic Micro-systems (Germany), V. Craciun - University of Florida (USA), M. Dinescu - National Institute for Laser Plasma and Radiation Physics (Romania), R. Eason - University of Southampton (UK), Q. Feng - Univ. of Science and Technology Beijing (China), E. Fogarassy - ENSPS Strasbourg (France), F. Garelie - Université Jean Monet Saint Etienne (France), D. Geohegan, Oak Ridge (USA), B. Gökce University Duisburg-Essen (Germany), J. Krüger - BAM Federal Institute for Materials Research and Testing (Germany), J.G. Lunney - Trinity College Dublin (Ireland), E. Millon - Université d'Orléans (France), S. Orlando - CNR-IMIP/PZ (Italy), A. Palla Papavlu – National Institute for Lasers, Plasma and Radiation Physics (Romania), N. Pryds - Risoe National Laboratory (Denmark), J. Perriere - INSP Paris (France), M. Pervolaraki - University of Cyprus (Cyprus), J. Schou - Risoe National Laboratory (Denmark), P. Schaaf - Technische Universität Ilmenau (Germany), Ekaterina Barmina- General Physics Institute, Moscow (Russia), R. Serna, J. Solis - CSIC, Instituto de Optica (Spain), M. Stratakis - FORTH-IESL (Greece), K. Zimmer - IOM Leipzig (Germany).


Papers accepted after normal review will be published in Applied Surface Science (Elsevier).

Submission Format and Guidelines:

We will be accepting submissions from Date until Date. Authors must follow Applied Surface Science’s Guide for Authors for formatting requirements ( To submit a paper, the author(s) must select “VSI: EMRS Laser Materials” as the special issue title. The submission website is located at

Each paper will be reviewed by the editor and papers that meet the journal’s requirements will be sent for anonymous peer review. Please note that being invited to submit to a special issue does not guarantee publication.

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Fundamentals of laser-material processing and nanofabrication : Tatiana Itina
Authors : Florent Calvo, G. Daniel Förster
Affiliations : Laboratoire Interdisciplinaire de Physique, CNRS and Universite Grenoble Alpes; Laboratoire d'Etude des Microstructures, ONERA and CNRS

Resume : Molecular dynamics simulations have been undertaken to unravel the role of kinetics on the morphologies of medium-size nanoparticles containing a few hundred to a few thousands of atoms produced from an initially very hot sample, as typically produced upon laser ablation of metal targets. In the case of aluminum ablated in oxygen atmosphere, the role of oxidation is essential on the eventually obtained nanoparticle. Structural analysis of the surface roughness of the nanoparticle is shown to exhibit non-monotonic dependence on the oxygen content, in agreement with experimental x-ray scattering measurements. Ablation of an iron-gold target will also be discussed, our simulations predicting a clear tendency to form metastable shapes such as onion-ring nanoparticles.

Authors : F. Stock1, F. Antoni1, D. Aubel2, S. Hajjar-Garreau2, D. Muller1
Affiliations : 1 ICube, D-ESSP, 23 rue du Loess, 67037 Strasbourg - France ; 2 IS2M, 15 rue Jean Starcky 68057 Mulhouse - France

Resume : One of the biggest challenge that will face optoelectronic and photovoltaic devices is the necessity to provide a reliable alternative to transparent conducting oxide (TCO) and especially to Indium Thin Oxide (ITO). We recently published a study proposing a method to produce transparent conductive electrodes only based on carbon materials. In a first step, we use the Pulsed Laser Deposition (PLD) elaboration technique to produce high performance DLC. Those thin films own very interesting properties in kindship with diamond, like high transparency in the visible range, chemical inertness and biocompatibility. In addition, the DLC is also a perfect electrical insulator. However, DLC is a material having a relative high opacity in the ultra-violet (UV) range. This particularity has a great interest to perform, in a second step, UV laser annealing over the DLC surface. The aim is to break the existing diamond bindings (sp3 hybridization) on the surface of the DLC layer and allow atoms to be reorganized in graphitic bindings (sp2 hybridization). We demonstrate that the increase of atomic graphitic bindings leads to an increase of the surface conductivity. According to adapted annealing parameters, the surface conductivity reaches values comparable to typical ITO performances. Regarding the transparency of the annealed layers, we show that the laser treatments only sparsely affects the DLC transparency. In this work, we also evaluate the performances of the conductive carbon layers and their use as transparent electronic components (resistor, capacitor and transistor). Moreover, this full laser-based process offers the advantage of being compatible with the standard microelectronic technological steps.

Authors : Dr. Indranath Chakraborty
Affiliations : ‡ Fachbereich Physik and Center for Hybrid Nanostructure (CHyN), Universität Hamburg, 22761 Hamburg, Germany.

Resume : Abstract: The ligand shell structure of the nanocluster1, Ag44(4-MBA)30 (MBA: mercaptobenzoic acid, in the thiolate form) was modified in a precise, site-specific manner.2 Laser irradiation at 633 nm of a monolayer assembly of plasmonic Ag nanoparticles (NPs) covered with Ag44(4-MBA)30 clusters leads to decarboxylation of 4-MBA ligands forming thiophenolate (TP) ligands. While the molecular identity and integrity of nanoclusters post laser irradiation were confirmed by ESI MS, time-dependent SERS spectra and computational studies suggest that the phenomenon of decarboxylation is limited to the 4-MBA ligands facing the NP surface. This creates modified Ag44 clusters, with 4-MBA ligands on one side and TP ligands on the other, giving them a two-faced (Janus) ligand structure. The ligand distribution of such clusters gets equilibrated in solution. We show that such selective transformation can be used to create molecular patterns. Janus clusters may be important in chemistry at biphasic interfaces. Reference: (1) Chakraborty, I.; Pradeep, T. Atomically Precise Clusters of Noble Metals: Emerging Link between Atoms and Nanoparticles. Chem. Rev. 2017, 117 (12), 8208. (2) Chakraborty, I.; Som, A.; Adit Maark, T.; Mondal, B.; Sarkar, D.; Pradeep, T. Toward a Janus Cluster: Regiospecific Decarboxylation of Ag44(4-MBA)30@Ag Nanoparticles. The Journal of Physical Chemistry C 2016, 120 (28), 15471.

10:00 Coffee break    
Authors : Cheng-Yu Shih, Chaobo Chen, Maxim V. Shugaev, Iaroslav Gnilitskyi, Leonid V. Zhigilei
Affiliations : University of Virginia, Department of Materials Science and Engineering, 395 McCormick Road, Charlottesville, VA 22904, USA; Research Center for Applied Sciences, Academia Sinica, 128 Academia Road, Section 2, Nangang, Taipei 11529, Taiwan; University of Modena and Reggio Emilia, Reggio Emilia, Italy

Resume : In this presentation, we will report the results of large-scale molecular dynamics simulations aimed at revealing the key processes contributing to the formation of nanoparticles and generation of periodic surface structures in pulsed laser ablation in liquids. In particular, the dependence of the nanoparticle formation on laser pulse duration and composition of the irradiated target will be considered, with a focus on the relative roles of (1) nucleation and growth in the cavitation bubble and (2) hydrodynamic instabilities at the interface between ablation plume and superheated liquid environment leading to the direct generation of large nanoparticles. The effect of the liquid environment on the formation of laser-induced periodic surface structures will also be discussed based on the results of large-scale atomistic simulations performed for Cr targets irradiated in vacuum and water environment. The shapes of the surface structures generated in the ablative regime will be compared to the results of experiments performed for the same systems and the same irradiation conditions.

Authors : Stella Maragkaki, Emmanuel Stratakis
Affiliations : Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas (IESL-FORTH)

Resume : Laser-induced periodic surface structures (LIPSS) or ripples are usually produced on polished surfaces with minor or random defects. Intensive experimental observations of LIPSS over a wide range of materials have been accompanied by theoretical studies. Still, it is very challenging to understand in deep in which way we can control the periodicity of these structures and how each mechanism contribute on the final morphology. Here we investigate the impact of the surface morphology on the spatial period of ripples by irradiating polished pre-patterned surfaces with a well-defined initial periodicity induced by an electron-beam.

Authors : I. Milov (1), N. Medvedev (2,3), V. Lipp (4), D. Ilnitsky (5,6), K. Migdal (5,6), V. Zhakhovsky (5,6), V. Khokhlov (5), Yu. Petrov (5,7), V. Shepelev (5,8), N. Inogamov (5,6), B. Ziaja (4,9), I.A. Makhotkin (1,10), E. Louis (1), and F. Bijkerk (1)
Affiliations : (1) MESA+ Institute for Nanotechnology, University of Twente, Drienerlolaan 5, 7522 NB Enschede, The Netherlands; (2) Institute of Physics, Czech Academy of Sciences, Na Slovance 2, 182 21 Prague 8, Czech Republic; (3) Institute of Plasma Physics, Czech Academy of Sciences, Za Slovankou 3, 182 00 Prague 8, Czech Republic; (4) Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany; (5) Landau Institute for Theoretical Physics, Russian Academy of Sciences, Chernogolovka 142432, Russia; (6) Dukhov Research Institute of Automatics (VNIIA), Rosatom, Moscow 127055, Russia; (7) Moscow Institute of Physics and Technology, Institutskiy Pereulok 9, Dolgoprudny, Moscow Region 141700, Russia; (8) Institute for Computer-Aided Design of the Russian Academy of Sciences, Vtoraya Brestskaya 19/18, Moscow 123056, Russia; (9) Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, 31-342 Krakow, Poland; (10) IMEC, Kapeldreef 75, 3001 Leuven, Belgium

Resume : Interaction of intense ultrashort laser pulses with solids creates highly excited non-equilibrium states of matter with high electron temperatures, but still at solid state density. Relaxation of such an excited system may lead to significant changes in the lattice structure of the irradiated target. Understanding such processes is necessary, e.g., to manufacture long lasting reflective optics for the rapidly developing x-ray free-electron lasers (XFELs). We study the interaction of fs laser pulses with Ru films in a wide range of incident photon energies (~1 - 104 eV). Since at XFELs reflective thin metal films operate at grazing incidence conditions, absorption of light occurs in the top part of Ru mirrors (~1 – 10 nm). Hybrid multi-scale modeling of target evolution after irradiation is performed. The model takes into account photoabsorption and non-equilibrium electron cascading occurring on a fs timescale, thermal diffusion and electron-phonon energy exchange on a ps timescale and lattice dynamics up to ns timescale. Different photon energies result in qualitatively different absorbed energy profiles by the time of thermalization of the electronic system. The effects of such a difference on the hydrodynamic evolution and eventual damage of Ru are discussed. Details of processes such as melting, cavitation, ablation and recrystallization are revealed for selected photon energies. The results show good qualitative agreement with the experimental observations on Ru ablation.

Authors : J. Bonse, S.V. Kirner, T. Wirth, H. Sturm, D. Spaltmann, J. Krüger
Affiliations : Bundesanstalt für Materialforschung und -prüfung (BAM)

Resume : The processing of laser-induced periodic surface structures (LIPSS, ripples) on metals and semiconductors in ambient air is usually accompanied by superficial oxidation effects – a fact that is widely neglected in the current literature. In this contribution, chemical, structural, and mechanical alterations in the formation of femtosecond LIPSS are characterized by a variety of surface analytical techniques, including energy dispersive X-ray analyses (EDX), X-ray photoelectron spectroscopy (XPS), micro Raman spectroscopy (µ-RS), and depth-profiling Auger electron microscopy (AEM). Alternative routes of electrochemical and thermal oxidation allow to qualify the relevance of superficial oxidation effects on the tribological performance in oil lubricated reciprocating sliding tribological tests (RSTT). It is revealed that the fs-laser processing of near-wavelength sized LIPSS on metals leads to the formation of a few hundreds of nanometers thick graded oxide layers, consisting mainly of amorphous oxides. Regardless of reduced hardness and limited thickness, this nanostructured surface layer efficiently prevents a direct metal-to-metal contact in the RSTT and may also act as an anchor layer for specific wear-reducing additives contained in the used engine oil.

Authors : Justas Baltrukonis, Orestas Ulčinas, Titas Gertus, Vytautas Jukna, Sergej Orlov
Affiliations : Center for Physical Sciences and Technology, Industrial laboratory for photonic technologies, Saulėtekio av. 3, Vilnius, Lithuania

Resume : The laser interaction with transparent materials using Gaussian beams is already well investigated. The need for speed of the fabrication process especially while cutting transparent materials creates a necessity to analyse various beam shapes and it is believed that the most beneficial of them would be the ones that have extended focus. The use of the Bessel beams that are nondiffractive enables to achieve that. In this study we analyse vector Bessel beam interaction with transparent material and foresee application to the microfabrication processes. The nondiffractive ring intensity profile enables to generate larger diameter beam without the need of altering the cone angle. We generate an extended void having high aspect ratio inside the transparent material with vector Bessel beams. We have also used the individual polarization components to observe the double void generation with a single shot. Additionally to the void formation we were able to generate microcracks by just changing the pulse duration. We have noticed a distinct pattern for crack formation in glass that is perpendicular to the two voids fabricated by the single pulse of one polarization of the vector Bessel beam. The damage thresholds for different vector Bessel beams and their polarization components are analysed and the proposals for their applications are formulated.

12:00 Lunch    
Formation and applications of nanoparticles and nanostructures : Jörn Bonse
Authors : Guillaume Baffou
Affiliations : Institut Fresnel

Resume : Gold nanoparticles can behave as ideal nanosources of heat remotely controllable by laser irradiation in the visible-nearIR range, thanks to a plasmon resonance effect enhancing optical absorption. This scheme opens the path for a large variety of investigations at small scales in various fields of science. This research thematics is named thermoplasmonics and currently encompasses applications such as photothermal cancer therapy, drug and gene delivery, single cell thermal biology, nanochemistry, heat-assisted magnetic recording, photothermal imaging, etc. In this presentation, after shortly presenting this field of research, I will focus on three recent works conducted at the Institut Fresnel, respectively in physics, chemistry and cell biology. In a first part, I will show how gold nanoparticle laser-heating revealed the ability to superheat a fluid on the microscale at ambient pressure, opening the path for high-temperature applications in chemistry. This latter application will be the topic of the second part of the talk, where gold nanoparticle heating is demonstrated to provide a powerful means to conduct hydrothermal chemistry at ambient pressure in an open medium, a new concept in chemistry. The last part will focus on the recent and rising field of research named single cell thermal biology. We developed a technique to measure temperature in living cells. This technique was used to control and monitor the heat-shock response at the level of single cells in cutlure, enabling a much faster dynamics compared to regular resistive heating of the sample.

Authors : Cécile Molto 1,2,3; Solène Bechu 2,3; Jung Eun Lee 2; Jan Nekarda 4; Varun Arya 4; Muriel Bouttemy 2,3; Arnaud Etcheberry 2,3; Etienne Drahi 2,5; Pierre-Philippe Grand 1,2; Anne-Marie Goncalves 2,3
Affiliations : 1 EDF R&D, IPVF, 30 route départementale 128, 91120 Palaiseau, France; 2 Institut Photovoltaïque d’Ile-de-France (IPVF), 30 route départementale 128, 91120 Palaiseau, France; 3 Institut Lavoisier de Versailles (ILV), Université de Versailles Saint-Quentin-en-Yvelines, Université Paris-Saclay , 45 avenue des États-Unis, 78035 Versailles, France; 4 Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstrasse 2, 79110 Freiburg im Breisgau, Germany; 5 TOTAL GRP-New Energies, Tour Coupole 32ème étage, 2 Place Jean Millier--La Défense 6, 92078 Paris La Défense Cedex

Resume : Nowadays, new metallization processes for n-PERT Si solar cells, such as Cu/Ni plating, are considered to replace screen-printing currently employed, to decrease the production costs (Al/Ag pastes use) and to increase the contacts quality. The contact realization requires an essential initial step consisting in the opening of the dielectric layers, usually performed by laser ablation as it enables high throughputs and can be reliably integrated into production lines. Nevertheless, the optimization of this preparative step is critical as it conditions the success of the electroless Ni deposition performed just after. Previous studies have underlined the importance to precisely control the laser to limit damages (Si emitter degradation …) and maintain an emitter surface as blank as possible. So, the modifications induced at the surface and deeper after laser opening are a critical point to understand, for both the polished rear one and the textured front one. To explore the laser parameter influence and optimize the operating conditions, we varied the peak fluence, spacing between two centers of the beam with different overlapping using a multi-technique approach combining imaging (CLSM, SEM), chemical (EDS, XPS), electrical (four probe measurements) and optical (ellipsometry) analyses. We have been able to propose an ablation mechanism as well as the best conditions to implement the laser opening and be favorable for a controlled Pd activation and selective Ni plating.

Authors : Stefano Danesi, Ivano Alessandri
Affiliations : INSTM-UdR Brescia, via Branze 38, 25123 Brescia, Italy Department of Mechanical and Industrial Engineering, via Branze 38, 25123 Brescia, Italy Department of Information Engineering, University of Brescia, via Branze 38, 25123 Brescia, Italy INO-CNR, via Branze 38, 25123 Brescia, Italy

Resume : Integrated electronics, photonics an optoelectronics need full control of lattice reconstruction processes in silicon nanostructures at the level of nanoscale. Light can be a powerful tool to trigger and control opto-thermal effects in resonant nanostructures. Here we propose a new computational approach to light-matter interactions in silicon nanopillars, which simulates heat generation and propagation dynamics occurring in continuous wave laser processing over a wide temporal range (from 1 fs to about 25 hours). We demonstrate that a rational design of the nanostructure aspect ratio, type of substrate, laser irradiation time and wavelength enables amorphous-to-crystalline transformations to take place with a precise, sub-wavelength spatial localization. In particular, we show that visible light can be exploited to selectively crystallize internal region of the pillars, which is not possible by conventional treatments. A detailed study on lattice reconstruction dynamics reveals that local heating drives the formation of secondary antennas embedded into the pillars. This approach can be easily extended to many types of nanostructured materials and interfaces, offering a unique computational tool for many applications involving opto-thermal processes (fabrication, data storage, sensing, catalysis, resonant laser printing, opto-thermal therapy etc…).

Authors : Hongfeng Ma, Said Bakhti, Zeming Liu, Nipun Sharma, Yaroslava Andreeva, Anton Rudenko, Francis Vocanson, Daniel S. Slaughter, Nathalie Destouches, Tatiana Itina
Affiliations : Laboratoire Hubert Curien, UMR CNRS 5516, UJM-Saint-Etienne, Univ. Lyon, Campus Manufacture, Saint-Etienne, 42000, France; Chemical Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; ITMO University, Kronverkskiy Pr. 49, St. Petersburg 197101, Russia

Resume : Nanocomposite materials have attracted continuously increasing interest due to numerous applications in photonics, optoelectronics, security and medicine. Laser-based fabrication of such materials is particularly promising since it allows unique control possibilities over the resulting optical properties of the films [1,2]. Despite numerous applications, the growth mechanism of NPs in porous matrixes is still under discussion. To bring more light on the involved physical and chemical processes, we present numerical results obtained during metal NPs formation in TiO2 porous films under scanning CW laser irradiation. In particular, the effects of temperature distribution on growth kinetics and particle diffusion are discussed. We also analyse optical properties of the obtained nanocomposite material and check the possibility of self-organisation effects in the film. To describe the underlying effects, we utilize an extended 2D model based on a combination of the heat conduction equation with the nonlinear growth kinetics of NPs. According to our calculations, the density and size distributions of the initial nanoparticles play significant roles in the kinetics of NPs formation due to the size-dependent absorption. Our model can also describe the unexpected experimental result, such as the higher temperature increase observed for higher scanning speed. Because even a very small temperature rises ahead of focal spot leads to changes in NPs size, the spatial distribution of laser energy absorption is considerably affected. Optical response of such structures depends on both the mean size and size distribution of NPs. The transmission and absorbance analysis of the obtained film showed a good agreement with the numerical results. [1] Liu Z. et al. Understanding the growth mechanisms of Ag nanoparticles controlled by plasmon-induced charge transfers in Ag-TiO2 films, The Journal of Physical Chemistry C. (2015), 119 (17) 9496-9505. [2] Liu Z. et al. Laser induced mechanisms controlling the size distribution of metallic nanoparticles, Physical Chemistry Chemical Physics (2016), 18 (35), 24600-24609.

Authors : Salvatore Surdo, Alessandro Zunino, Alberto Diaspro, Martí Duocastella
Affiliations : Nanophysics Department, Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genova, Italy.

Resume : Optical techniques for the high-throughput processing of materials on the nanoscale are of great relevance for several applications such as photonics and electronics. Among others, methods based on interference of multiple beams are particularly attractive because they enable large area sub-wavelength patterning of a wide range of materials. However, current approaches are limited in speed, ease of use, cost of implementation, and pattern flexibility. To address these challenges, we realized an acusto-optofluidics (AOF) device capable of generating tailored light intensity patterns in real time. The device consists of two pairs of parallel piezoelectric plates oriented along orthogonal directions in a water-filled cavity. By driving each piezoelectric pair with an arbitrary periodic signal, the cavity sustains acoustic standing waves. These latter allowed us to generate 3D diffraction patterns with topology that can be user-selected by adjusting the parameters (e.g. amplitude, frequency) of the driving signals. By combining the AOF device with both a fast XYZ stage and laser direct writing system we sculpted nanostructures over indefinitely large area of a target substrate, being limited only by the stage travel range. Here, we provide a theoretical background, a full experimental characterization of our device, and demonstrate its broad range of applications by writing, in both subtractive and additive modalities, centimeter-squared areas within minutes.

15:30 Coffee break    
Authors : Ernestas Nacius, Pavel Gotovski, Sergej Orlov, Orestas Ulčinas, Titas Gertus
Affiliations : State research institute Center for Physical Sciences and Technology, Industrial Laboratory for Photonic Technologies, Sauletekio ave 3 LT-10222, Vilnius, Lithuania

Resume : Zeroth order Bessel beams are well known for their diffraction-less properties as well as for their long focal region and the number of their applications in laser micromachining is steadily expanding. Higher order Bessel beams are also called Bessel vortex beams. They became attractive in various applications due to their non-zero optical angular moment. For an example they are actively used for atom guiding or as optical tweezers for nanoobject manipulation. Flexible generation of higher order Bessel beams can be achieved using a spatial light modulator (SLM), which is a flexible tool, commonly used in generation and experimental verification of various beam shaping scenarios. In this work we develop novel technique for realization of superimposed complex Bessel beam vortices of different orders. Moreover we control their position and intensity in the focal region individually to enable creation of complex patterns not only in the transverse plane but also along the focal line. We present experimental verification of our approach using phase-only SLM masks. Lastly, we report on an inscription in the bulk of fused silica some phase masks of those superimposed Bessel beams with engineered axial profiles. This approach to diffractive optical elements (DOEs) is based on a proven concept of the geometrical phase and enables us to investigate the performance of those complex patterns in high power laser and matter interaction scenarios.

Authors : K. V. Khishchenko
Affiliations : Joint Institute for High Temperatures RAS, Moscow, Russia

Resume : Models of equations of state and phase transformations of materials are required for numerical simulations of processes of intense pulsed influences on condensed media. In the present work, equations of state for aluminum and copper are proposed with taking into account melting and evaporation effects. As distinct from the previous multiphase equations of state, new expressions for the thermodynamic potentials are formulated. Those provide for a more correct thermal contribution of heavy particles in the liquid phase under rarefaction. A critical analysis of calculated results is made in comparison with available experimental data for the metals over a wide range of densities and temperatures. Presented equations of state can be used efficiently at modeling of intense laser-material interactions.

Authors : Miguel Alvarez1, Marina Garcia1, Fatima Cabello1, Emmanuel Haro-Poniatowski2, Rosalia Serna1, and Jan Siegel1
Affiliations : 1. Laser Processing Group, Instituto de Óptica, IO-CSIC, Serrano 121, 28006 Madrid, Spain 2. Departamento de Física, 2 Departamento de Química, Universidad Autónoma Metropolitana Iztapalapa, Av. San Rafael Atlixco No. 186, Col. Vicentina, C.P. 09340, México D. F. México

Resume : Nanocomposite systems based on bismuth nanoparticles (Bi NPs) have received a growing interest due to the demonstration of plasmon-like resonances that can be tuned in the visible-UV region, and that have found applications for integrated photonic devices, surface enhanced spectroscopy and plasmonic enhanced photocatalysis.[1,2] Furthermore, due to the low melting temperature of Bi, these systems are also candidates for its use as optical switches by profiting from the different optical properties of solid and liquid Bi [3]. Here we study the solid-liquid phase change of Bi NPs embedded in amorphous aluminium oxide film upon nanosecond laser excitation by using single pulse real time reflectivity measurements with nanosecond resolution. The changes of the reflectivity reveal that melting takes place within the nanosecond pulse duration whereas cooling and solidification of the NPs occurs over time scales that are much longer than for bulk Bi. The solid-liquid switching time is found to depend on the nanoparticle density, and it can be controlled smoothly from 10 ns to 700 ns by adjusting the laser pulse fluence. The optical switching process is found to be repeatable more then 10,000 times without observable degradation. [1] J. Toudert, et al. J. Phys. Chem. C 121, 3511 (2017). [2] J. Toudert and R. Serna, Opt. Mater. Express 7, 2299 (2017). [3] M. Jiménez De Castro, F. Cabello, J. Toudert, R. Serna, and E. Haro-Poniatowski, Appl. Phys. Lett. 105, (2014).

Poster : Nicu Scarisoreanu, Cristian Focsa, Stela Canulescu
Authors : D. Kuczynska-Zemla (1), A. Sotniczuk (1), M. Pisarek (2), P. Kwasniak (1), H. Garbacz (1)
Affiliations : (1) Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw, Poland; (2) Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland

Resume : Direct Laser Interference Lithography (DLIL) results in creation of multimodal surface topography of the titanium, which according to the literature improve its biological properties. In spite of that, to obtain satisfied biological activity of the Ti surface good corrosion resistance and mechanical properties are also necessary. Therefore in this study, the corrosion resistance and mechanical properties of titanium after DLIL processing were analyzed. Method presented in this study was developed in order to locally functionalize the surface of prefabricated elements with original roughness. The titanium after two commonly used surface modification in biomedical applications (shot peening and acid etching) was subjected to the DLIL patterning. As a result of laser processing, using Nd:YAG laser with the following parameters the pulse duration 10 ns, energy density 400 mJ/cm2 and 7 laser pulses, we obtain two different surface patterns ? grooves and island micrometer in size. The corrosion resistance was analyzed in solution simulating the effects of body fluids (37°C), and the mechanical properties were evaluated by nanoindentation tests. Obtained results were analyzed in correlation with the surface characteristics such as topography, surface chemical and phase composition and microstructure beneath free surface. The results showed that laser processing results in improvement of corrosion resistance and mechanical properties of the surface. The factors responsible for this beneficial effects will be presented as well. This research was financially supported by The National Science Centre Poland under Grant no. 2016/23/N/ST8/02044.

Authors : Łukasz Haryński, Jakub Wawrzyniak, Piotr Kupracz, Jakub Karczewski, Katarzyna Grochowska, Katarzyna Siuzdak
Affiliations : The Szewalski Institute IMP PAN, 80-231 Gdańsk, Fiszera 14 st., Poland; Gdańsk University of Technology, 80-233 Gdańsk, Narutowicza 11/12 st., Poland

Resume : Titanium dioxide nanotubes (TiO2NTs) are usually obtained via electrochemical oxidation that is regarded as a relatively simple, inexpensive technique which allows to control the geometry of NTs. Since as-anodized TiO2NTs exhibit amorphous phase, calcination is usually performed to obtain crystalline phase. However, the whole process covering heating of samples and their cooling down to room temperature can take over 10 h, therefore it is important to elaborate a new, time- and cost-reducing technique enabling phase conversion. In this work, we present a phase conversion of 600-nm long free-standing TiO2NTs by means of pulsed Nd:YAG laser as an alternative for the furnace annealing accompanied with their modification by transition metal species. NTs were obtained via anodization in diethylene glycol based electrolyte at elevated temperature followed by deposition of 5 nm-thin metal film. Free-standing NTs were chosen for a better light harvesting whereas metal species affect optical and photoelectrochemical properties. The effects of 355 nm laser treatment at 2Hz frequency was studied by scanning electron microscopy, Raman and UV-vis spectroscopies, in order to reveal the impact of laser radiation on morphology, crystallinity and absorbance, respectively. Preliminary investigations have shown that the phase conversion can be achieved by laser radiation under the examined conditions. This work has been financed by National Science Centre under grant no 2017/26/E/ST5/00416.

Authors : Manto Logotheti, Simos Papazoglou, Filimon Zacharatos, Ioanna Zergioti
Affiliations : School of Applied Mathematics and Physical Science, National Technical University of Athens, Zografou Campus, 15780, GR

Resume : Current technological trends in flexible and larger area electronics require the precise deposition of highly resolved features, in a direct writing approach which preserves their structural and electronic properties upon transfer. This paper will present Laser Induced Backward Transfer (LIBT) of metals and 2D materials as a reliable, high resolution and versatile fabrication tool for flexible electronics, sensors and optoelectronic components. LIBT configuration involves a laser pulse directed through a transparent receiver substrate towards the interface of a transparent donor and its carrier substrate where it is absorbed, resulting in the transfer of a pixel onto the receiver. LIBT can be used to generate precisely shaped metal nanostructures from metal film donor substrate materials. In particular, this paper highlights the application of LIBT for metallic thin film pixels on flexible or stretchable substrates (PEN or PDMS), using short pulsed nanosecond and picosecond lasers. Controllable transfer of different sizes of pixels for metallic electrodes will be demonstrated: the printed pixels have lateral size from 15-100 μm, and form factors suitable for applications in flexible and large area electronics. Furthermore, results from LIBT of 2D materials, e.g. graphene, will be demonstrated either by transferring directly single layer graphene from monolayer CVD-grown graphene or by “exfoliating” graphene layers on-demand starting from Highly Oriented Pyrolytic Graphite (HOPG).

Authors : Stefano Danesi, Marco Gandolfi, Luca Carletti, Nicolò Bontempi, Costantino De Angelis, Francesco Banfi, Ivano Alessandri.
Affiliations : INSTM-UdR Brescia, via Branze 38, 2513 Brescia, Italy; Department of Mechanical and Industrial Engineering, via Branze 38, 2513 Brescia, Italy; Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP) and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via Musei 41, 25121 Brescia, Italy; Laboratory of Soft Matter and Biophysics, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium; Department of Information Engineering, University of Brescia, via Branze 38, 2513 Brescia, Italy; 6INO-CNR, via Branze 38, 2513 Brescia, Italy.

Resume : Light-to-heat conversion in non-plasmonic nanoantennas is a key topic for many applications, including photo-thermal therapy, Raman sensing, laser writing and nanofabrication. Heat generation and propagation in non-plasmonic systems is increasingly debated, and contradictory results have been reported so far. Here we report an experimental evidence and a Finite Element Analysis of temperature distribution and heat flow in SiO2/Si core/shell systems (silicon nanoshell) irradiated with a continuous wave laser (λ =532 nm). The complex interplay among optical proprieties, morphology, degree of crystallinity of the nanoshells, thickness dependence of thermal conductivity and interactions with the substrate has been elucidated. Finally, we report the possibility to use localized heat generation, to selectively induce changes in the chemical composition of a-Si nanopillar. The FEA model was extended to account for the temperature-induced chemical reaction. The model follow the time and space evolution of the chemical change, refractive index, temperature, and light-structure interaction.

Authors : Mihaela Filipescu1, Gheorghe Dinescu1, Nicu D. Scarisoreanu1, Floriana Craciun2, Maria Dinescu1*
Affiliations : 1 National Institute for Laser, Plasma and Radiation Physics,Atomistilor 409, 077125 Magurele, Romania 2CNR-Istituto di Struttura della Materia, Area della Ricerca di Roma - Tor Vergata, Via del Fosso del Cavaliere, 100, 00133, Rome, Italy

Resume : Pulsed Laser Deposition was demonstrated to be an attractive technique for PZT thin films growth. Influence of a radiofrequency discharge addition in different gases (Oxygen, Argon, mixture Oxygen/Argon) on the piezoelectric, ferroelectric and dielectric properties of PZT thin films deposited by pulsed laser deposition are reported. A parametric study related to gas pressure/RF power was carried out in conjunction with substrate temperature and incident laser wavelength and fluence variation

Authors : S. Sanchez1, G. García-Mandayo1, I. Ayerdi1, M. Hopkinson2, D. Li3, S.M. Olaizola1, E. Castaño1
Affiliations : 1 Ceit and Tecnun, University of Navarra, San Sebastian, Spain; 2 Department of electronic and electrical engineering, University of Sheffield, Sheffield, UK; 3 JR3CN&IRAC, University of Bedforshire, Luton, UK;

Resume : In an AACVD process, precursors are dissolved in a solvent, and a nebulizer generates an aerosol. These droplets are transported to the chamber reactor by a carrier gas where the chemical reactions occurred to form the desired film. This technique has some advantages in comparison to conventional CVD; for instance, it has a wider availability of precursors, easier delivery and vaporization of the precursors and a higher deposition rate. In an AACVD standard process the reaction is thermally activated by heating the substrate where the deposition takes place. The aim of the present study is to increase even more the advantages, therefore, a new technique for the thermal activation of the reaction has been probed; the pulsed laser-enhanced aerosol assisted chemical vapor deposition (LEAACVD). This technique is a one-step deposition of ZnO thin films and direct writing of structures, which is a breakthrough toward faster thin films deposition techniques. LEAACVD has been implemented through a custom designed reaction chamber with an optic viewport for the wavelengths; 355, 532 and 1064 nm, and capacity for substrates of 3 and 4 inches. The fabrication of LEAACVD ZnO films with a fully controlled deposition rate and morphology has been achieved. This innovative fabrication process is expected to have a strong influence in electro-optical devices.

Authors : A. De Bonis, A. Galasso, M. Curcio, A. Santagata, R. Teghil
Affiliations : A. De Bonis; A. Galasso; M. Curcio; R. Teghil Dipartimento di Scienze, Universita della Basilicata, Via dell’Ateneo Lucano 10, 85100 Potenza, Italy A. Santagata CNR-ISM, U.O.S. Tito Scalo, C.da S. Loja, 85050 Tito Scalo, Italy

Resume : Hydrothermal carbonization (HTC) of biomasses is widely used to obtain hydrochar and can be followed by pyrolisis for producing microporous materials with high carbon content (> 90-95 wt%) and high surface area. The ablation of these materials by an ultra-short pulse laser can be a useful method to produce thin films of nanostructured carbon materials with several applications. In this work wast single-varietal plant biomasses have been used as starting materials for HTC and the pyrolized matrices obtained as final product have been ablated by a frequency doubled Nd:glass laser with a pulse duration of 250 fs. The ablated material has been deposited on different substrates and analyzed by X-ray diffraction, scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The first steps of the films growth have been studied by transmission electron spectroscopy. The functional properties of the films deposited on steel have also been evaluated in electrochemical devices for reversible energy storage (lithium non-aqueous batteries) to test the possible use as electode components in microbatteries.

Authors : Christopher Smith; James Shaw-Stewart
Affiliations : WMG; M-Solv

Resume : The use of Li-ion batteries (LIBs) in electric vehicles (EVs) is increasing the need to improve and optimise LIB manufacture. Lasers are often used in various manufacturing settings, but in LIB cell manufacture this is normally limited to welding the electrode tabs together, although even then there are other welding techniques more often used. We demonstrate areas in which laser processing may be useful in LIB electrode manufacture, particularly in cutting the electrodes into shape, but also for laser processing of the electrode surface, including to revitalise reclaimed electrodes for remanufacture. For the negative electrode the most conventional chemistry of graphite on copper foils has been used, and for the positive electrode aluminium coated in Li-metal oxide (where the metal is a mixture of Ni, Mn & Co) has been used. As electrodes are usually double sided and can vary in thickness from 10 to 200 um, thick double-sided electrode coatings have been used to demonstrate the capability of low-cost laser machining tools to carry out the electrode cutting. The process of electrode cutting has been tested with varying pulse lengths to investigate a phenomenon known as the heat affected zone (HAZ). It has been found that by lowering the pulse length down to the picosecond range that this HAZ is minimised. In the future further tests will be undertaken with ultrashort pulses to see if the HAZ can be eliminated completely while making sure the process is fast enough to compete with mechanical blanking.

Authors : Stefan Andrei Irimiciuc1, Bianca Hodoroaba2, Georgiana Bulai3, Silviu Gurlui3, Valentin Craciun1
Affiliations : 1National Institute for Laser, Plasma and Radiation Physics – NILPRP, 409 Atomistilor Street, Bucharest, Romania; 2University of Bucharest, Faculty of Physics, Bucharest-Magurele, Romania; 2Faculty of Physics, Atmosphere Optics, Spectroscopy and Lasers Laboratory, “Alexandru Ioan Cuza” University of Iasi, 700506 Iasi, Romania

Resume : Here we report on optical investigations of laser produced plasmas (LPP) on pyrolytic graphite generated by ns - laser ablation in various experimental conditions in terms of pressure and laser fluence. The aim of this work was to investigate the fundamental mechanisms behind molecule formation and their effect on the overall plasma dynamics. The transient plasma plumes were generated by focusing ns- laser beam (Nd-YAG, 10 ns, 10 Hz) with various fluences ranging from 2.5 J/cm2 to 15 J/cm2. The dynamic of the LPP were altered by the changes in the residual background pressure which was varied from 1·10-3 to 100 Torr. The ICCD images revealed the separation of the plasma plume into multiple structures. At longer periods of time the second “atomized structure” subsequently splits intro tree components: one central and two symmetrically positioned towards the outside of the plasma volume. The two plasma structures observed at the edges of the plasma volume mainly contain C2 molecules, while on the plume front’s edge molecules like CN can be found. The individual dynamics for each of the molecules, atoms and ions was also investigated. We observed that highly energetic particles like C or N ions which can be found in the front on the plume, while atomized species were found in the vicinity of the target at longer times than the ionized species. For the investigations performed at high pressures the plasma dynamics are discussed in the framework of a turbulent flow hypothesis and non-linear analysis revealed a chaotic movement of the ejected atoms and ions.

Authors : Hauke Honig, Dong Wang, Erich Runge, Christoph Lienau, Peter Schaaf
Affiliations : TU Ilmenau, Institute of Materials Science and Engineering and Institute of Micro and Nanotechnologies, 98693 Ilmenau, Germany; TU Ilmenau, Institute of Materials Science and Engineering and Institute of Micro and Nanotechnologies, 98693 Ilmenau, Germany; TU Ilmenau, Institute of Physics and Institute of Micro and Nanotechnologies, 98693 Ilmenau, Germany; University of Oldenburg, Institute of Physics, Center of Interface Science, 26129 Oldenburg, Germany; TU Ilmenau, Institute of Materials Science and Engineering and Institute of Micro and Nanotechnologies, 98693 Ilmenau, Germany;

Resume : Individual gold nanosponges (nanoporous gold nanoparticles) which were fabricated by solid state dewetting of Ag/Au bilayers and subsequent dealloying [1], are reconstructed from SEM images captured by FIB nanotomography. The investigated particles have diameters in the range of a few hundred nanometers and ligament diameters around 12 nm. For the resolution of single ligaments in radial direction the slicing is performed with a step size of 2 nm. Two different materials, C and Cr, were used as first layer of the protective film on top of the sliced particles. The choice of that material contacting the particle has significant influence on the analyzability of captured images. Ligaments in the background could be separated from those in the image plane from in-lens secondary electron images. From the 3D reconstructed nanosponges, the Au volume fraction is calculated and compared with the volume ratio of the bilayers and the shrinkage observed during the dealloying process. The specific internal surface area computed from the 3D data is approximately 12 m²/g which matches well results from TEM tomography and electrochemical measurements of the internal active surface area of nanoporous gold with similar geometries [2]. The optical and plasmonic properties of the gold nanosponges are clearly different from that of the solid nanoparticles, and are more complex and fascinating due to unique structural feature [3, 4]. In order to better understand the structure-property-relation, the optical properties have been simulated with Finite-Difference Time-Domain (FDTD) method [3-6]. However, due to the complexity of the porous structure, it is very difficult to build a model with the exact same percolated porous structure with mathematic methods, and the models used in literatures [3-6], were simplified and constructed with a large gold sphere etched by randomly distributed spherical air pores. In this work, the 3D reconstructed models of gold nanosponges, which correspond precisely to the real structures, have been used for the simulation. The results show that the plasmon peak shifts red and multiple resonances behavior appear with increasing porosity. The dipole characteristic in the field distribution declines also with increasing porosity. [1] Wang, D. & Schaaf, P., Nanoporous gold nanoparticles, J. Mater. Chem., The Royal Society of Chemistry, 2012, 22, 5344-5348. [2] Fujita, T.; Qian, L.-H.; Inoke, K.; Erlebacher, J. & Chen, M.-W., Three-dimensional morphology of nanoporous gold, Applied Physics Letters, AIP, 2008, 92, 251902. [3] Vidal C., Wang D., Schaaf P., Hrelescu C., Klar T.A., Optical Plasmons of Individual Gold Nanosponges. ACS Photonics 2015, 2, 1436-1442. [4] Rao W., Wang D., Kups T., Baradács E., Parditka B., Erdélyi Z., Schaaf P., Nanoporous Gold Nanoparticles and Au/Al2O3 Hybrid Nanoparticles with Large Tunability of Plasmonic Properties. ACS Appl. Mater. Interfaces 2017, 9, 6273–6281. [5] Vidal, C., Sivun, D., Ziegler, J., Wang, D., Schaaf, P., Hrelescu, C., Klar, T. A., Plasmonic Horizon in Gold Nanosponges. Nano Lett 2018, 18, (2), 1269-1273. [6] Hergert, G., Vogelsang, J., Schwarz, F., Wang, D., Kollmann, H., Groß, P., Lienau, C., Runge, E., Schaaf, P., Long-lived electron emission reveals localized plasmon modes in disordered nanosponge antennas. Light Sci. Appl. 2017, 6, e17075.

Authors : A. Riveiro (1), T. Abalde (1), R. Soto (1), J. del Val (1), P. Pou (1), R. Comesaña (2), F. Lusquiños (1), J. Pou (1)
Affiliations : (1) Applied Physics Department, University of Vigo ETSII, Lagoas-Marcosende, 9. Vigo, 36310, SPAIN; (2) Materials Eng., Applied Mech., and Construction Dpt., Universidade de Vigo, EEI Vigo, SPAIN

Resume : PTFE is a synthetic fluoropolymer showing an excellent resistance to the attack of almost any chemical, high-temperature mechanical properties, high flexural strength or low friction coefficient. Such properties make it very interesting for its use in many different industrial fields, such as in tubing, seals, air filters or as dental filling. Due to its large stability, and hydrophobic nature, the wetting properties of PTFE surfaces can be promoted to enhance the hydrophobicity and transform them into superhydrophobic. In this regard, laser texturing is a fast, simple and versatile method to produce PTFE superhydrophic surfaces in one-step, and over large areas. In this work, we used a CO2 laser to modify the surface of PTFE flat samples. We studied the effect of the processing parameters (laser power, scanning speed, beam overlap) on the wetting behaviour of water, oil and ethanol/water solutions. Laser-treated surfaces show a hierarchical micro- and nanotopography with a cotton-like appearance promoting a large air trapping. The higher roughness and air trapping make laser-treated surfaces superhydrophobic and highly oleophobic. Contact angle for ethanol/water solutions was also largely increased. The present findings suggest that CO2 laser texturing of PTFE could be applied for the large-scale preparation of low wetting surfaces to different liquids, with practical application in fields, such as self-cleaning surfaces, microfluidic devices, drag reduction or liquids separation.

Authors : M. Scarisoreanu1, A.G. Ilie1, C. Fleaca1, A.M. Banici1,2, I.P. Morjan1, E. Dutu1,I.I. Lungu1 , F. Dumitrache1 , V.Teodorescu 3, A. Sandulescu4, I. Balint4
Affiliations : 1 National Institute for Lasers, Plasma and Radiation Physics, 077125, Magurele-Bucharest, Romania; 2 University of Craiova, Faculty of Mathematics and Natural Sciences, 200585, Craiova, Romania 3 National Institute of Materials Physics, Magurele, Romania 4Romanian Acad, Inst Phys Chem Ilie Murgulescu, 202 Spl Independentei, Bucharest 060021, Romania

Resume : This work presents the preparation of NM (noble metal: Au, Ag, Pt) modified- TiO2 nanoparticles using laser pyrolysis technique. The two-step synthesis process consisted in pyrolysis of C2H4-TiCl4 precursor mixture, in the presence of air, followed by chemical impregnation of collected materials with the aquous solution of noble metal precursors (AgNO3, KAuCl4, H2PtCl6). Nanomaterials with optimized structural, morphological and optical properties were produced at different synthesis parameters. The synthesized nanomaterials were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, energy-dispersive X-ray spectroscopy (EDX) and UV–vis diffuse reflectance spectroscopy (DRS) techniques. Photodegradation of perchloroethylene (PCE) performed in UV and VIS light shows that noble metals presence on TiO2 surface enhances drastically the photocatalytic activity, especially in the cases of Au- and Pt-modified TiO2. The higher efficiency in photodegradation processes observed in case of noble metals addition to titania nanoparticles can be ascribed to (i) better separation of electron–hole pairs at metal-oxide interfaces and (ii) catalytic noble metal-enhanced redox processes, taking place betwen photogenerated charges and organic substrate.

Authors : A.A. Samokhin, E.V. Shashkov, N.S. Vorob’ev, A.E. Zubko
Affiliations : Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991, Moscow, Vavilov Str., 38

Resume : Acoustical monitoring of nanosecond laser-metal interaction using modulated laser intensity is demonstrated recently in our paper [JETP Letters, 108(6), 364–367] for a tin–lead alloy (POS61 solder) located on acoustical transducer surface. Difference between modulation of acoustical response and laser intensity during laser irradiation shows relative time delay which corresponds to effective displacement d(t) of acoustic signal source which initially moves away and then approaches the acoustic transducer. In the present report instead of solid target a liquid Hg is used and d(t) behavior is rather different at approximately the same laser fluences. As in case of solid target at lower fluences E < 1 J/cm2 d(t) is constant except for initial several tens of nanoseconds where d(t) is diminishing due to probably cleaning effect at the irradiated surface. In contrast to the solid case at higher fluences d(t) continues to diminish and then begins to grow at later irradiation times. The resulting minimum of d(t) occurs at somewhat earlier time t at higher laser fluences and it amounts to several microns recess at sound velocity 1.4 km/s. The recess exceeds the estimated value of ablation depth at given E values probably due to cleaning effect and temperature variation of sound velocity. It should be mentioned that in the steady-state ablation regime the temperature variation of sound velocity does not affect the relation between the measured time delay and displacement d.

Authors : N.E. Stankova1, N.N. Nedyalkov1, A.S. Nikolov1, E. Iordanova2, , G. Yankov2, V. Mihajlov2, L. Aleksandrov3, R. Iordanova3
Affiliations : 1 Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee blvd., 1784 Sofia, Bulgaria, 2 Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko shousse blvd., 1784 Sofia, Bulgaria, 3 Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. Georgi Bonchev str. bld.11, 1113 Sofia, Bulgaria,

Resume : This study investigates the photonic effects induced in noble metal enriched borosilicate glass by using different laser processing approaches. Short and ultrashort laser pulses generated in the UV-ViS-NIR spectrum are used for direct patterning of the samples. Photonic (optical and plasmonic) effects arise after further thermal annealing and/or irradiation with laser light. By varying some critical laser parameters (wavelength, fluence, pulse duration, number of pulses) can control the special periodicity of the pattern and its structure and thus to tune the plasmon-resonance response. Different methods of investigation of the optical and structural properties are applied: UV-Vis spectroscopy, x-ray photoelectron spectroscopy, optical and scanning electron microscopy. Such patterned structures have met great of interest for different applications such as sensing, SERS, photonics, photovoltaics. Also, the direct laser patterning is easy controllable and suitable method for single-step fabrication approach.

Authors : Vincenzo Amendola,1, Elti Cattaruzza,2, Anna Tymoczko,3, Marius Kamp,4, Lorenz Kienle,4, Christoph Rehbock,3, Stephan Barcikowski,3
Affiliations : 1- Department of Chemical Sciences, University of Padova, via Marzolo 1, I-35131 Padova, Italy 2- Department of Molecular Sciences and Nanosystems, Università Ca’ Foscari Venezia, via Torino 155/b, I-30172 Venezia-Mestre, Italy 3- Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University Duisburg-Essen, Universitätstr. 7, 45141 Essen, Germany 4- Faculty of Engineering CAU Kiel, Institute for Materials Science, Synthesis and Real Structure, Kaiserstraße 2, 24143 Kiel, Germany

Resume : Laser ablation in liquid (LAL) emerged as a powerful technique for the synthesis of multielement nanoparticles (NPs) such as metal alloys with thermodynamically forbidden composition. Consequently, there is a great interest in expanding the current knowledge about NPs formation during LAL, in order to improve the control on product structure and to extend the range of compositions accessible by this technique. Here we discuss about the results obtained so far with laser ablation synthesis in solution of nanoalloys with magnetic and plasmonic properties and metastable phase. In particular, we show how the systematic investigation carried out by laser ablation of thin metallic films by changing target structure, liquid environment and pulse length provided useful insight about the formation mechanism of homogeneous nanoalloys and about how to switch from homogeneous to core-shell nanoparticles. These results are of interest for the general understanding of the processes behind the LAL technique and for the production of multifunctional nanomaterials which are appealing in a wide range of applications from catalysis to photonics and nanomedicine.

Authors : Linda Pabst, Robby Ebert, Horst Exner
Affiliations : Laserinstitute Hochschule Mittweida

Resume : High pulse repetition rate ultrashort pulse laser technology facilitate a precise micro-machining of different materials. Due to the use of ultra-short pulse laser the machining quality and the precision can be significant improved compared to processing with longer pulse durations. By increasing the pulse repetition rate the processing speed increases and the laser technology, therefore, is suitable for rapid tooling. In this study, fundamental research on the ablation behavior of Nickel-Chromium-alloy sheet metal was carried out. For this, a femtosecond laser (λ = 1030 nm, τH = 180 fs) with a pulse repetition rate up to 1 MHz in combination with a galvanometer scan system capable of up to 8 m/s was applied. The influence of processing parameters such as fluence, pulse number, pulse repetition rate and scan speed on the ablation process was examined. Single and multiple pulse irradiation on polished NiCr alloy sheet metal was implemented to determine the ablation threshold as well as the incubation factor of the material. Furthermore, small areas were generated with various processing parameters to determine the ablation rates and with this the processing efficiency. The obtained machining qualities were evaluated by use of surface SEM analysis and optical micrographs, furthermore, the ablation depths were measured using a laser scanning microscope. The micro machining of NiCr alloy sheet metal was then optimized regarding to process efficiency and processing quality.

Authors : A. Mariscal1, S. Negrete-Aragón2,3, M. García-Pardo1, E. Soria1,4, C. Sánchez-Aké 3, J. Gonzalo1, R. Serna1
Affiliations : 1 Laser Processing Group, Instituto de Optica, IO-CSIC, Serrano 121, 28006 Madrid, Spain 2 Facultad de Ciencias, UNAM, Av. Universidad 3000, Circuito Exterior S/N, Coyoacán, 04510, Ciudad Universitaria, Ciudad de México, México 3 Grupo de Fotofísica y Películas Delgadas, Departamento de Micro y Nanotecnologías, Instituto de Ciencias Aplicadas y Tecnología, UNAM, Av. Universidad 3000, Circuito Exterior S/N, Coyoacán, 04510, Ciudad Universitaria, Ciudad de México, México 4 SAFTRA Photonics, Jesenná 5, 040 01 Košice Slovakia.

Resume : Transparent conductive oxides (TCO’s) have been widely used as transparent electrodes for solar cells and mobile display panels because they present unique properties of coexistence of visible transparency and electronic conduction. One of the more used and extended is the Indium Tin Oxide (ITO), however Indium is scarce and this has motivated the investigation of new TCO’s based on more abundant elements and with capability of tunable properties. In this context, molybdenum oxides are semiconductors with different optical and electronic properties depending on their stoichiometry: MoO3 presents transparency showing a wide bandgap (>3 eV), whereas MoO2 is a semimetal [1]. Upon introducing oxygen defects in MoO3, gap states can be generated effectively changing its response and allowing to the tunability of the material properties. In this contribution we will show the strategies that we are developing to deposit MoOx by PLD. We achieve the successful growth of MoOx films from a MoO3 target by using different starting background vacuum conditions. The films stoichiometry and therefore their optical response is further tuned by post-deposition annealing in air in up to 400ºC. We have studied the evolution of the dielectric function as a function of the deposition and post-annealing conditions in order to obtain films with optimized transparency. [1] I. A. de Castro, et al.,Adv. Mater. 29, 1–31 (2017).

Authors : A.Yu. Kharin1 ,V.A. Oleshenko2,1, A.F. Alykova2, O.V. Karpukhina3, A. A. Grigoryev1,2, , N.V. Karpov1, S.M. Klimentov1, V.V. Bezotosniy2, I.N. Zavestovskaya1, 2 , A.V. Kabashin1,4, V.Yu. Timoshenko1,2,5
Affiliations : 1 National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) Kashirskoe sh., 31, 115409, Moscow, Russia 2 Lebedev Physical Institute of the Russian Academy of Sciences, 53 Leninskiy Prospekt, 199991, Moscow, Russia 3 Lomonosov Moscow State University, Faculty of Biology, Leninskie Gory 1, 119991, Moscow, Russia 4Aix-Marseille University, UMR 7341 CNRS, LP3, Campus de Luminy–Case 917, 13288 Marseille Cedex 9, France 5 Lomonosov Moscow State University, Faculty of Physics, Leninskie Gory 1, 119991, Moscow, Russia

Resume : We report on preparation and characterization of silicon nanoparticles, produced by laser ablation in liquid for applications as light absorbers for photohyperthermia under near-IR laser excitation. While as-prepared silicon nanoparticles can rapidly degrade into water solution with degradation kinetics dependent on the pH level of the aqueous medium, the polymer coating (dextran, PEG) can prevent rapid degradation of the nanoparticles and it can be used to control their dissolution rate. The polymer coating provides the pH-independent and much slower kinetics of the nanoparticles’ dissolution without any change in their light absorbance. Photoinduced heating of silicon nanoparticles aqueous suspensions under continuous and pulsed excitation with IR (808 nm) laser radiation was investigated. A regime for increasing the aqueous suspension temperature above 40oC was revealed. In vitro experiments with cells of Paramecium Caudatum were carried out and their results indicated that silicon nanoparticles are promising sensitizers for local hyperthermia under IR irradiation.

Authors : A. L. Sortino, M. Censabella, G. Munzi, S. Boninelli, F. Ruffino, V. Privitera
Affiliations : A. L. Sortino CNR-IMM via S. Sofia 64, 95123 Catania, Italy; M. Censabella CNR-IMM via S. Sofia 64, 95123 Catania, Italy Dipartimento di Fisica e Astronomia “Ettore Majorana”, Università di Catania, via S. Sofia 64, 95123 Catania, Italy; G. Munzi CNR-IMM via S. Sofia 64, 95123 Catania, Italy; S. Boninelli CNR-IMM Strada VIII, 5, 95121 - Catania, Italy; F. Ruffino CNR-IMM via S. Sofia 64, 95123 Catania, Italy Dipartimento di Fisica e Astronomia “Ettore Majorana”, Università di Catania, via S. Sofia 64, 95123 Catania, Italy; V. Privitera CNR-IMM via S. Sofia 64, 95123 Catania, Italy;

Resume : Gold nanostructures (Au NSs) are exploited to fabricate innovative sensing devices. They capture great interest due to size-dependent structure and properties, high specific surface area and reactivity. The success of such technologies is subjected to the development of simple, versatile, low-cost, high-throughput methods for the NSs controlled production. Thus, we present a laser-assisted synthesis method to fabricate Au NSs and their exploitation as optical sensors of glyphosate. In particular, colloidal solutions of Au NSs are produced by nanosecond-pulsed laser ablation of Au target in liquid environment. The morphological, structural and optical characterization of the NSs is performed as a function of the ablation process parameters and of the presence of citrate in solution during the ablation step. Then, the variation of the optical properties of the Au NSs colloidal solutions versus the amount of added glyphosate in solution is studied. In fact, glyphosate is one of the most widely used herbicides in the world whose presence is, often, detected in cereals and whose effect on the health is a subject of wide debate. By our studies, we show that the Au NSs (with optimized size and morphology) solutions can be used as highly sensitive optical sensor for detection of glyphosate. Due to feasibility and cost-effectiveness, this approach is a promising alternative to the standard complex analytical procedures for glyphosate detection.

Authors : P.A. Atanasov*1, N.N. Nedyalkov1, N. Fukata2, W. Jevasuwan2, T. Subramani2
Affiliations : 1Institute of Electronics, Bulgarian Academy of Sciences, Tsarigradsko Chaussee 72, Sofia 1784, Bulgaria 2International Center for Materials for NanoArchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044, Japan

Resume : This presentation will express our preliminary results on SERS analyses of neonicotinoid insecticides in quantities smaller than usually applied in agricultural medicine. Advanced Ag and Au nanostructures created by laser techniques on different substrates are applied. Nova days, the neonicotinoid insecticides are very discussible over the world. In fact, three of them (thiamethoxam, imidacloprid and clothianidin) are subject of restriction in the EU since April 2018 because of the threat they pose to bees. The proposed study is forwarded directly to bearing on the environment and human health as detection of residue of harmful pollutants.

Authors : Tina Viertel; Linda Pabst; Robby Ebert; Horst Exner
Affiliations : Laserinstitute Hochschule Mittweida

Resume : In recent years, several applications for the laser ablation of thin metal layers from the glass substrate side have been studied. The rear side ablation is a highly effective ablation method for thin layer structuring and revels a high structuring quality. Therefore, the present work deals with the selective rear side ablation of thin aluminum layers on fused silica with ultrashort pulsed laser radiation (λ = 1028 nm and tH = 0.2 - 10 ps). The influences of process parameters (fluence, pulse number and pulse duration) and layer thickness (10 - 50 nm) on the ablation thresholds as well as the incubation coefficients were determined. Laser scanning- and atomic force microscopy were used to characterize the ablation craters. Thereby, different morphologies were observed dependent from process parameters. In addition to experimental investigations, theoretical calculations were carried out to determine the melting and evaporation threshold fluences of aluminum. The theoretical values were compared with experimental data. With the help of these investigations, the quality of the structuring of aluminum layers can be improved.

Authors : Erieta-Katerina Koussi, Florent Bourquard, Teddy Tite, Florence Garrelie, Yves Jourlin
Affiliations : Université de Lyon, Université Jean Monnet-Saint-Étienne, CNRS, Institut d’Optique Graduate School, Laboratoire Hubert Curien UMR 5516, F-42023, Saint-Étienne, France

Resume : Vanadium dioxide is well-known for its thermoelectric and thermochromic properties in the infrared and microwave range, transiting from a transparent dielectric at room temperature to an absorbent insulator at temperature as low as 60 to 70 °C. Using a KrF laser, vanadium oxide films are synthesized by pulsed-laser deposition (PLD) using metallic vanadium or vanadium pentoxide targets, in various oxygen pressure, on different kinds of substrate, such as quartz, fused silica, glass and titanium dioxide. Several annealing procedures are performed, using an in situ ultra-high vacuum oven or a Rapid Thermal Processing device, at temperature ranging from 300 °C to 550 °C, in various oxidizing atmospheres and duration. Thermochromic transition parameters are studied by transmission spectroscopy and ellipsometry, and Raman and AFM analysis are performed. We demonstrate the possibility to obtain VO2-like transition on numerous substrates, notably amorphous ones, with annealing temperatures much below 500 °C, processing durations of only few minutes and thin films thickness as low as 25 nm. A reasonable control of the transition temperature and the hysteresis parameters can be reached by carefully selecting the oxygen pressure during PLD and the annealing temperature. Those very thin thermochromic films deposited on substrate such as fused silica or TiO2 are then used in a multilayer coating to produce a thermally controlled resonant grating.

Authors : Maria Chiara Sportelli (a,b), Maurizio Clemente (a), Margherita Izzi (a), Annalisa Volpe (b), Antonio Ancona (b), Rosaria Anna Picca (a,c), Gerardo Palazzo (a,c), Nicola Cioffi (a,c)
Affiliations : (a) Chemistry Department, University of Bari “Aldo Moro”, via E. Orabona 4, 70126, Bari, Italy; (b) IFN-CNR, Physics Department “M. Merlin”, via Amendola 173, 70126, Bari, Italy; (c) CSGI (Center for Colloid and Surface Science) c/o Dept. Chemistry, via Orabona 4, 70125, Bari, Italy.

Resume : Laser ablation synthesis in solution (LASiS) is a well-known method to produce pure metal nanocolloids [1]. Interestingly, LASiS-generated metal NPs are generally highly stable, without adding any capping agent [2]. In this work, silver nanoparticles were prepared by LASiS in isopropanol, a polar organic solvent. Different experimental parameters were tested, and NP stability over months was studied. In order to make some hypotheses about the stabilization mechanism of our nanoparticles, we made a systematic study on both fresh and aged colloids. The rationale for this extreme stability of metal nanoparticles suspended in organic solvents is to look for in DLVO theory. Based on theoretical considerations and straightforward experiments it is proposed that the stabilization of silver nanoparticles involves the formation of an organic coating generated by the interaction of isopropanol molecules with the pulsed, high-energy laser beam. This coating prevents, on the one hand, any chemical reaction on colloidal nanoparticles (e.g. silver oxidation); on the other hand, the presence of the organic shell with a nature akin to that of the organic solvent led to weaker Van der Walls interactions between approaching nanoparticles enabling a larger stability than for naked metallic nanoparticles. [1] V. Amendola et al., J. Chem. Soc. Faraday Trans. 11 (2009), 3805–3821 [2] M.C. Sportelli et al., Colloids Surf. A 559 (2018) 148–158

Authors : Eitan edri, Nina Armon, Udi Greenberg and Hagay Shpaisman
Affiliations : Bar-Ilan University, Department of Chemistry and Institute for Nanotechnology and Advanced Materials, Ramat Gan 5290002, Israel.

Resume : Among conductive polymers, polyaniline (PANI) has attracted considerable attention due to its unique electrical and optical behavior which makes it a central candidate for formation of various electronic devices. One of the main challenges in the micro-fabrication process of PANI is to maintain its high conductivity and structure integrity. Here we present a method that allows micro-fabrication of patterned PANI with excellent conductivity. We focus a laser beam close to a surface covered with a dispersion of PANI in n-methyl-2-pyrrolidone (NMP). The laser light locally heats the dispersion until a microbubble is formed. Convection currents around the microbubble carry PANI nanoparticles to the bubble/substrate interface where they are pinned to the substrate. By moving the substrate relative to the laser continuous patterns with ~2µm resolution are formed. We show that the deposited PANI could be doped with HCl leading to conductivity of 1.5×10^3 s/m.

Authors : E. Napolitani(1), R. Milazzo(1), A. Ballabio(2), J. Frigerio(2), Y. Hou(3), M. Scuderi(4), K. Gallacher(5), R. Millar(5), V. Giliberti(6), L. Baldassarre(6), F. Mazzamuto(7), K. Huet(7), M. Ortolani(6), D.J. Paul(5), G. Nicotra(4), G. Capellini(3,8), and G. Isella(2)
Affiliations : (1) Dipartimento di Fisica e Astronomia, Università di Padova and CNR-IMM, Via Marzolo 8, I-35131 Padova, Italy; (2) L-NESS, Dipartimento di Fisica, Politecnico di Milano, Polo di Como, Via Anzani 42, I-22100 Como, Italy; (3) IHP, Im Technologiepark 25, D-15236 Frankfurt (Oder), Germany (4) IMM-CNR, Z. I. VIII Strada 5, I-95121 Catania, Italy (5) School of Engineering, University of Glasgow, Rankine Building, Oakfield Avenue, Glasgow G12 8LT, United Kingdom; (6) Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Rome, Italy (7) Laser systems and solutions of Europe (LASSE), SCREEN Semiconductor Solutions Co., Ltd., 14-38 rue Alexandre, Bldg D, 92230 Gennevilliers, France; (8) Dipartimento di Scienze, Università degli Studi Roma Tre, I-00154 Roma, Italy

Resume : The integration of highly doped Ge on Si with a controlled amount of tensile strain is crucial for several applications in advanced nanoelectronic and photonic devices. However, obtaining n-type doping above 5x1019cm-3 and in-plane biaxial tensile strain above +0.2-0.25 % with conventional growth and annealing methods is highly challenging. Here we report on the combination of in‑situ doping of Ge-on-Si epilayers and pulsed laser melting (PLM) to improve the activation of phosphorous in germanium and increase the tensile strain. Secondary ion mass spectrometry measurements indicate that the box-like profile of as-deposited epilayers is preserved during PLM with minimal P out-diffusion. An activated n-doping concentration above 1e20 cm^-3 over 2-300 nm thick layers has been achieved, as measured by infrared reflectivity. High Resolution X-Ray Diffraction and Raman measurements show that, after PLM, the in-plane residual thermal strain reaches +0.6%. Concurrently, planar defects form as observed by Transmission Electron Microscopy. Such structural modifications are promoted by the extremely high thermal gradients achieved by PLM, as indicated by heat flow simulations. Thanks to the heavy doping and to the extremely high tensile strain, a significant Photoluminescence intensity increase is observed after PLM, with a clear evidence of the Fermi level being above the conduction band Gamma valley minimum.

Authors : Sergej Orlov, Paulius Šlevas, Pavel Gotovski, Justas Baltrukonis, Vytautas Jukna, Orestas Ulčinas, Titas Gertus
Affiliations : State research institute Center for Physical Sciences and Technology, Industrial Laboratory for Photonic Technologies, Sauletekio ave 3, LT-10222, Vilnius, Lithuania

Resume : Pseudo-nondiffracting vortices are widely used for various applications like optical tweezers or laser microfabrication. Due to their high length to width ration they are usually called “optical bottles”. In this work we with start with construction of an “optical bottle”, which in contrary to a Bessel vortex beam has an arbitrary intensity distribution. We analyze ways to change the spatial position of the “optical bottle” either in focal region of a lens, or in the Fresnel region of a diffractive element. Next, we introduce a spatial array of independent “optical bottles” and report on physical limitations due to mutual interference of individual beams. In order to verify our theoretical considerations and numerical simulations we employ a spatial light modulator and experimentally observe controllable spatial arrays with various numbers and spatial separations of individual beam. Lastly, we examine laser microprocessing of transparent glasses using those engineered beams.

Authors : Satoshi Kurumi, Kaoru Suzuki
Affiliations : Nihon University

Resume : Titanium oxide based photocatalyst materials have brought about great benefits in our lives as a green-chemistry application such as a hydrogen generator and a pollution reducer etc. However, most photocatalyst materials are able to only react with ultra violet light irradiation owing to its high energy gap. Because of these reason, discovering more less energy gap photocatalyst materials has been expected so as to response with visible light irradiation. Therefore, we attempted on to produce photocatalyst films which are capable of reacting under visible light irradiation using strontium and lanthanum composed titanium oxide films in this study. Photocatalyst films were produced by a pulsed laser deposition method. A strontium titanium oxide substrate and a laser target, which was prepared by mixed three kinds of powders (strontium oxide, lanthanum oxide and titanium oxide) and pressed, were set into a vacuum chamber. Argon and/or oxygen gasses pressure of the chamber was controlled by mass flow controller. A focused Nd: YAG laser beam (wavelength: 355 nm, fluence: 300 mJ/cm2, pulsed width: 20 nm, 30000 shots) was irradiated as a laser ablation source. Ablation plums were deposited on the substrate which was heated by a ceramic heater (max: 900 degree). La doped SrTiO3 films was synthesized on the substrate. After the PLD, transmittance of visible to ultraviolet region of the produced films were measured in order to estimate their energy gap values. The result of transmittance spectra showed values of energy gap were 2.1 to 3.2 eV. It depended on La doping amount. This indicates it is probable that produced films can be useful to react with visible light irradiation by their photocatalystic reaction.

Authors : Pierre Lorenz1, Marcel Himmerlich2, Martin Ehrhardt1, Mauro Taborelli2, Béla Hopp3, Klaus Zimmer1
Affiliations : 1 Leibniz Institute of Surface Engineering (IOM), Permoserstraße 15, 04318 Leipzig, Germany 2 CERN, European Organization for Nuclear Research, 1211 Geneva 23, Switzerland 3 University of Szeged, Dóm tér 9, Szeged 6720, Hungary

Resume : Irradiation of metals by ultrashort laser pulses facilitates easy and fast fabrication of nanostructured surfaces. These surfaces appear dark and exhibit interesting physical properties for industrial applications like low optical reflectivity and low secondary electron yield. Polycrystalline copper surfaces were irradiated by ps-laser radiation with wavelength of 355 nm, and 1064 nm, respectively. The laser irradiation was performed in air as well as nitrogen and oxygen ambient. The controlled movement of the laser beam across the copper surface by a galvanometer scanner allows the defined overlapping of the laser spot and finally the fabrication of a homogenous large-area nanostructured copper surface. The morphology and composition of the nanostructured surface was analyzed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The laser treated Cu exhibits low optical reflectivity (R), as analyzed by UV/VIS-spectrometry, and a low secondary electron yield (SEY) down to 0.7 for the energy range between 10 and 1800 eV. The impact of the laser process parameter and of the ambient gas on the formed nanostructures, the optical reflectivity and the SEY is presented and discussed.

Authors : Pierre Lorenz1, Michael Klöppel-Gersdorf2, Igor Zagoranskiy1, Martin Ehrhardt1, Frank Frost1, Klaus Zimmer1
Affiliations : 1 Leibniz Institute of Surface Engineering (IOM), Permoserstraße 15, 04318 Leipzig, Germany; 2 Fraunhofer-Institut für Verkehrs- und Infrastruktursysteme IVI, Zeunerstraße 38, 01069 Dresden

Resume : The fast and well-defined fabrication of surface nanostructures attracts still high industrial interest. Laser self-organization processes open the way for the cost-effective fabrication of surface nanostructures with sizes below the optical diffraction limit. Such laser melting and reshaping process for µm- und sub-µm surface structure generation can be optimized by supporting simulations. UV-photo and nanosphere lithographically produced periodic chromium structures on a fused silica substrate were irradiated by a KrF excimer laser with a wavelength of 248 nm and a pulse duration of 25 ns. Low fluence irradiation of these pre-structured samples results in the temporal melting of the chromium patterns. The surface tension forces mass transport processes in the liquid chromium causing a temporally increasing reshaping of the initial chromium structures until their resolidification. This reshaping process is stopped by resolidification of the chromium and different intermediate states of shape modifications can be “frozen” depending on the laser fluence; the lateral geometry can be well below the resolution of the used lithography for pre-patterning. The achieved surface structures were studied by atomic force (AFM) and scanning electron microscopy (SEM) and characterized in dependence on the laser parameters and the initial metal pre-patterns. The metal film reshaping process was simulated by coupling the heat equation (description of laser-solid interaction and phase transition) with a special formulation of Navier-Stokes equation (mass transport in the liquid) using co-simulation. The simulation findings are in good agreement with the experimental results.

Authors : M. Barbuta1, A. Marcu2, F.Dumitrache2, C.Fleaca2, R.Ungureanu2, A. Achim2, C.Diplasu2, G.Giubega2, M.Serbanescu2
Affiliations : 1Faculty of Applied Sciences, “Politehnica” University, Splaiul Independentei nr. 313, 060042 Bucharest, Romania 2 Center for Advanced Laser Technologies (CETAL), National Institute for Laser, Plasma and Radiation Physics (INFLPR), Atomistilor 409, Magurele 077125, Romania.

Resume : Laser irradiation of various materials has plenty of applications, from CD players to material processing (cutting drilling and so on) and medical applications. There are special cases when the laser beam needs to target a precisely determined zone or the target needs to be in a rather narrow laser focus zone, and these are the cases when the beam alignment becomes a critical issue. If the target is not rigidly fixed or ‘shakes’ from the beam (photonic or plasma) impulse, then the difficulty of the targeting operation increases further, particularly if we wish to deliver multiple pulses on the precisely same spot area. The aim of this paper is to present an implementation of laser targeting system for a moving target based on a real-time impulse transfer measuring and movement prediction algorithms. Computer modeling software was developed based on a template matching algorithm and a predictive algorithm for target motion using Prony’s Method. The algorithms are implemented using Python and open-sources libraries. Presented experimental system involves 3 basic movement (in polar coordinates) while target position data acquisition is based on an aliment laser and a fast CCD camera for the movement detection. The experimental setup and the logical flow of the program are presented and discussed. The ‘targeting’ performance is shown along with the main (spatial and temporal) performances. Experimental results on measurements of laser-impulse transfer to metallic targets for few laser beam parameters are presented together with few results for multiple laser shots. Some near-future applications in laser-matter interactions are also proposed.

Authors : D. Kuczynska-Zemla (1), P. Kwasniak (1), M. Pisarek (2), A. Chlanda (1), M. Spychalski (1), R. Ostrowski (3), A. Rycyk (3), H. Garbacz (1)
Affiliations : (1) Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw, Poland; (2) Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland; (3) Institute of Optoelectronics, Military University of Technology, Warsaw, Poland

Resume : The main aim of this study is to demonstrate that by using the direct laser interference lithography (DLIL), the physicochemical properties of surfaces can be modified in a locally controlled manner. In this experiment DLIL method was applied to produce periodic grooved pattern on titanium surface. The titanium polished surface was structured using a Nd:YAG laser with the following parameters: 1064 nm wavelength, the pulse duration 10 ns, energy densities between 100 - 900 mJ cm-2 and single laser pulse. The width of the pattern was the same for all applied energy densities, approx. 10 µm. The obtained structures were characterized in terms of shape, roughness, chemical composition and mechanical properties. In order to achieve all information, numerous of research methods have been used: scanning electron microscopy, atomic force microscopy, optical profilometry, X-ray photoelectron spectroscopy and nanoindentation measurements. For analysis of the physicochemical properties of the surface, the water contact angle tests were performed. The results obtained in this study will be transferred for more complex, real surface topographies of biomedical devices. The systematic comparison of surface structures will be useful to evaluate suitability of presented method as an single step treatment for local surface functionalization for implantable devices with complex topography. This research was financially supported by The National Science Centre Poland under Grant no. 2016/23/N/ST8/02044.

Authors : Christoph Rehbock, Frederic Stein, Stephan Barcikowski, Meike Stiesch
Affiliations : Technical Chemistry I, University of Duisburg-Essen, Essen, Germany, ; Technical Chemistry I, University of Duisburg-Essen, Essen, Germany, ; Technical Chemistry I, University of Duisburg-Essen, Essen, Germany, ; Department of Prosthetic Dentistry and Biomedical Materials Science, Hannover Medical School, Hannover, Germany,

Resume : The bactericidal effects of silver nanoparticles (Ag-NP) against multiresistent bacteria is well known, however, their cytotoxicity and consequently the narrow therapeutic window limits their applicability. Furthermore, there are only very few studies on the bacterial uptake of Ag-NP and how it is linked to bioactivity. In this study we use silver-gold alloy nanoparticles as antimicrobial agents, which were synthesized by pulsed laser ablation in liquids. This process does not need any organic ligands as stabilizers and thus avoids potential toxic cross-effects. The ablated particles show a completely homogeneous elemental distribution of the elements gold and silver on a single particle level and a composition identical to that of the ablated bulk target. It can be shown that there is a non-linear decrease of the bactericidal effects with an increasing gold molar fraction, originating from an inhibition of Ag dissolution by the more noble metal gold. Related studies on the cellular uptake of AgAu alloy nanoparticles by the bacterium S. aureus revealed that only small particles could be found in the bacteria, which, interestingly, were significant more silver rich than the original particles. Based on these findings we conclude that these silver rich particles were probably formed by dissolution and intercellular reduction of silver ions. With the help of these results we may begin to understand the mechanism behind the cellular toxicity of silver nanoparticles.

Authors : LN Kolotova, SV Starikov
Affiliations : Joint Institute for High Temperatures of the Russian Academy of Sciences

Resume : In this work, the femtosecond laser pulse modification of surface is studied for silicon by use of two-temperature atomistic simulation. The surface modification after laser irradiation can be caused by ablation and melting. For low energy laser pulses, the nanoscale ripples may be induced on a surface by melting without laser ablation. Laser ablation occurs at a higher pulse energy when a crater is formed on the surface. The ablation thresholds of surface ablation by ultrashort laser pulse of variable width at various temperatures of silicon are calculated. The results of simulation are in good agreement with experimental data for silicon. Also, the dependence of the modification depth (ablation or melting) on absorbed fluence is obtained.

Authors : Z. Harajli, M. Soueidan, D. Fabregue, Z. Herro, M. Tabbal
Affiliations : Materials Science and Engineering Department, INSA Lyon, 25 Avenue Jean Capelle 69621 Villeurbanne, France; Department of Physics, Lebanese University Faculty of Sciences 2, P.O. Box 90656, Jdeidet El-Metn, Lebanon; Lebanese Atomic Energy Commission - CNRS, Airport Road, PO Box 11-8281, Beirut, Lebanon; Department of Physics, American University of Beirut, Bliss St., P.O. Box: 11-0236, Beirut, Lebanon;

Resume : Due to its high phonon group velocity, Aluminum Nitride (AlN) is a material of choice for the manufacturing of efficient semiconductor heat sinks. Thus, the multilayered system, Cu/AlN/Cu, is excellent for usage in electronic packages power, transistors and IC packages in which heat removal is crucial for maintaining the normal functioning of these devices. However, at high temperatures, the mismatch between the thermal expansion coefficient of Cu and that of AlN causes cracks in the layers leading to system. In this work, we propose Molybdenum (Mo) as a promising candidate to substitute copper substrates and fabricate the new high temperature system. Mo has a thermal expansion coefficient that is close to AlN and thus is expected to provide a very useful multilayer heat sink that can hold even at high temperatures and/or for thermal cycling. We have thus grown Mo thin films on commercially available AlN substrates by pulsed laser deposition technique. The obtained thin films were characterized by x-ray diffraction, scanning electron microscope, and atomic force microscopy. The effect of different experimental parameters, particularly growth temperature and background argon pressure, was investigated to achieve lowest surface roughness, highest purity as well as best crystallinity conditions. It was found that deposition under an argon atmosphere leads to better crystallinity, and lower roughness as well as greater growth rate compared to films grown under vacuum. Well crystallized layers were obtained at growth temperature of 600 C and above. A significant reduction in droplets’ formation at the surface of the films is observed at an argon pressure of 50mTorr and growth temperatures exceeding 800 C.

Authors : A.V. Mazhukin, V.I. Mazhukin, M.M. Demin, A.V. Shapranov, A.A. Aleksashkina
Affiliations : Keldysh Institute of Applied Mathematics of RAS, National Research Nuclear University MEPhI

Resume : Using the molecular dynamics method, temperature and pressure dependences of the thermophysical characteristics of copper (Cu) were constructed in a wide range of temperatures T and pressures P. Temperatures ranged from room temperature T=300 K to critical temperature T=Tcr. The pressure values covered the range from 1bar to 100 kbar. In molecular dynamics calculations, special attention was paid to the temperature regions of phase transformations and near the critical region of matter. It was taken into account that phase transitions of the first kind imply the presence of metastable states associated with overheating of the solid phase during melting and supercooling of the liquid during crystallization. Determination of the thermophysical properties of the metal in the vicinity of the critical region and the parameters at the critical point (temperature, density, pressure) was carried out according to the original molecular dynamics method. A comparison of the simulation results with numerous experimental and theoretical results showed that despite some disagreements between them, most of the results obtained for Cu are in good agreement with the experimental and theoretical data. The simulation results in this study will contribute to the accumulation of data necessary for the continuum models used in studies of femto-picosecond laser action on metals. This work was supported by RSF, project 18-11-00318.

Authors : Ru.G. Nikov1,*, A.Og. Dikovska1, S. Amoruso2,3, G. Ausanio2,3, N.N. Nedyalkov1
Affiliations : 1 Institute of Electronics, Bulgarian Academy of Sciences 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria 2 Dipartimento di Fisica, Università di Napoli Federico II, Via Cintia I-80126 Napoli, Italy 3 CNR-SPIN UOS Napoli, Via Cintia I-80126 Napoli, Italy

Resume : In this work is demonstrated fabrication of magnetic composite nanowires composed by arranged nanoparticles. The structures are produced by the pulsed laser deposition process performed in the presence of an external magnetic field. The depositions are carried out in air at atmospheric pressure by using nanosecond laser pulses delivered from Nd:YAG laser system operated at wavelength of 1064 nm. The high density of the environment result in condensation of the ablated material forming nanoparticles which are rapidly arranged into nanowires due to the external magnetic field applied. Samples composed by iron oxide and silver with different ratio between them were produced. The formed composite nanowires are few microns in length and have orientation parallel to the magnetic field lines. The influence of the sample composition on the morphology and optical properties of the structures is investigated. An analysis on the magnetic properties of the composite nanowires is also carried out. The presented structures could be used in the design of novel nanoelectronics, spintronics and magneto optics devices.

Authors : Ralph Delmdahl, Jean-Luc Tapié, Matthias Trenn, Arnold Gillner
Affiliations : Coherent LaserSystems GmbH & Co. KG, Hans-Boeckler-Str. 12, Goettingen, Germany; Fraunhofer ILT, Steinbachstr. 15, 52074 Aachen, Germany

Resume : A novel UV line beam system for large area processing will be introduced. The linear beam concept dispenses with movable components such as scanner optics. By using a fixed line beam with ns pulse duration and combining it with a 150 W excimer laser as the beam source a system with optimum reproducibility of the resulting layer modification has been created. Depending on the application, the excimer laser beam can be redirected into a high-resolution mask ablation system with rectangular field geometry. This machine’s modular concept can be used for a wide range of materials. Materials with a depth resolution below 0.1 μm can be modified over large area. Moreover, selective structuring of sensitive multilayer systems is achieved without causing thermal damage. The functionality of the novel line beam system and the attainable layer quality are evaluated individually and form the basis for rapidly implementing the UV system in industrial applications. Treating large areas in minimum time is pivotal in achieving reduced unit costs in high-volume production. Excimer lasers meet the requirements for clean and precise structuring and enable the smallest structures in an efficient way. The latest technical development in high power excimer lasers is bound to take cost-efficient UV-laser processing to the next level and bridges the gap between achievable precision and throughput.

Authors : JyotsnaDutta Majumdar1**, Renu Kumari1,2+, Wilhelm Pfleging3,5*,Heino Besser3#
Affiliations : 1Dept. of Metal. & Maters. Eng., I. I. T. Kharagpur, W. B. – 721302 2Dept. of Metal. & Maters. Engg., NIT, Jamshedpur, Jharkhand 3 Karlsruhe Institute of Technology, IAM-AWP, P.O. Box 3640, 76021 Karlsruhe, Germany 5 Karlsruhe Nano Micro Facility, H.-von-Helmholtz-Pl. 1, 76344 Egg.-Leopoldshafen, Germany

Resume : In this presentation, studies on ultrafast laser surface processing of titanium has been conducted to induce nanostructured surface in micro-textured titanium. Surface texturing and nanostructuring has been achieved by ablation of surface using ultrafast (ns or fs) laser. The detailed investigations undertaken in the present study include surface texturing and nano-structuring of Ti6Al4V using ArF laser and femto second laser, which ablated the materials from the surface of polished Ti6Al4V for topographical and microstructural modification. The effect of laser ablation on surface topography, microstructure, composition and phases has been discussed in details. In addition, the wear resistance and corrosion resistance properties of the laser ablated surface have also been discussed. Laser surface texturing using KrF laser leads to the development of linear textured zone with the average width of 30 m and thickness of 5 m. Femtosecond laser processing leads to the development of nanostructured surface with the average grain size of 5-10 nm with the presence of residual compressive stress on the surface. The optimum process parameters for the formation of textured surface (by KrF laser) and nanostructured surface (by femtosecond laser) has been derived.

Authors : Valentina Dinca1, Cristian Viespe1, Nicu Scarisoreanu1, Simona Brajnicov1, Izabela Constantinoiu1, Laurentiu Rusen1, Toader Constantin Nicolae2, Maria Dinescu1
Affiliations : 1 National Institute for Lasers, Plasma and Radiation Physics, Magurele RO, Bucharest, Romania 2 Scientific Research Center for CBRN Defense and Ecology, Bucharest, Romania

Resume : Enzymatic interfaces based on Acetylcholinesterase-Polyethylenimine hybrid and multilayered coatings were obtained by Matrix assisted pulsed Laser Evaporation-MAPLE for sensing application. The interface characteristics in terms of surface chemistry, thickness, roughness were tailored by laser deposition parameters and target characteristics. The deposition process of the polymer and enzyme was carried out using an Nd:YAG pulsed laser, operating at 0.45J/cm2 fluences with a wavelength of 266 nm and a repetition rate of 10 Hz and a double target system. The main functional groups in the MAPLE-deposited thin films determined by Fourier transform infrared spectroscopy revealed the similarity with the molecular structures of the initial material. The morphologies revealed by Atomic Force Microscopy and Scanning Electron Microscopy shown smooth surfaces, with roughness below 6 nm. The sensors were tested upon exposure to Dimethyl Methylphosphonate DMMP and Diisopropyl Methylphosphonate DIMP, showing, for each of the sensors, a different sensitivity to the selected chemical agents. The best sensitivities for DMMP and DIMP, obtained by using a PEI-AchE coated sensor, are 65 kHz and 200kHz, respectively, whereas the best sensitivity when using multilayered interfaces is 30kHz, respectively 10KHz for DIMP and DMMP. Acknowledgment: Financial support from Nucleu Program 2019 is acknowledged.

Authors : Stefano Danesi, Marco Gandolfi, Luca Carletti, Nicolò Bontempi, Costantino De Angelis, Francesco Banfi, Ivano Alessandri.
Affiliations : INSTM-UdR Brescia, via Branze 38, 2513 Brescia, Italy Department of Mechanical and Industrial Engineering, via Branze 38, 2513 Brescia, Italy Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP), Via Musei 41, 25121 Brescia, Italy Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via Musei 41, 25121 Brescia, Italy Laboratory of Soft Matter and Biophysics, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium Department of Information Engineering, University of Brescia, via Branze 38, 2513 Brescia, Italy INO-CNR, via Branze 38, 2513 Brescia, Italy

Resume : Light-to-heat conversion in non-plasmonic, high refractive index nanonatennas is a key topic for many applications, including Raman sensing, laser writing, nanofabrication and photo-thermal therapy. However, heat generation and propagation in non-plasmonic antennas is increasingly debated and contradictory results have been reported so far. Here we report a Finite Element Analysis of steady-state temperature distribution and heat flow in SiO2/Si core/shell systems (silicon nanoshells) irradiated with different continuous wave lasers (532, 633 and 785 nm), under real working conditions. The complex interplay among optical properties, morphology, the degree of crystallinity of the nanoshells, thickness dependence of thermal conductivity and interactions with the substrate has been elucidated. This study reveals that all of those parameters can be properly combined to obtain either stable nanoshells for Raman sensing or highly efficient sources of local heating. The optimal balance between thermal stability and field enhancement was found for crystalline Si shell layers with a thickness ranging from 40 to 60 nm, irradiated by a NIR laser source. On the other hand, non-conformal amorphous or crystalline shell layers with thickness >50 nm can reach very high local temperature (above 1000 K) when irradiated with low power density (less than 1 mW/m2) laser sources. This work provides a general approach for an extensive investigation of the opto-thermal properties of high-index nanoantennas.

Authors : J. Bonse (1), C. Plamadeala (2), P. Fosodeder (2), M. Muck (2), O. Armbruster (2), H. Habibzadeh (2), W. Baumgartner (3), A. Weth (3), C. Steinwender (4), H. Blessberger (4), J. Kellermair (4), S. V. Kirner (1), J. Krüger (1), A. Shaukat Lone (5), A. W. Hassel (5), J. Heitz (2)
Affiliations : (1) Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin, Germany; (2) Institute of Applied Physics, Johannes Kepler University Linz, Austria; (3) Institute of Biomedical Mechatronics, Johannes Kepler University Linz, Austria; (4) Department of Cardiology, Kepler University Hospital Linz, Austria; (5) Christian Doppler Laboratory for Combinatorial Oxide Chemistry (at ICTAS), Johannes Kepler University Linz, Austria

Resume : Due to its excellent strength-to-weight ratio, good corrosion resistance, and excellent biocompatibility titanium alloys are widely used for medical implants. Apart from the surface topography also surface chemistry plays a decisive role that affects the adhesion of biological cells on titanium alloy surfaces. In this work, Ti6Al4V titanium alloy samples were scan-processed with femtosecond laser radiation (800 nm, 30 - 120 fs, 1 kHz) and then electrochemically treated. Surface characterization by electron microscopy revealed that the fs-laser processing can generate hierarchical micro-nanostructures as micrometric spikes, covered by nanometric laser-induced periodic surface structures (LIPSS, ripples). Contact angle measurements indicated that the laser-induced surface roughness along with the electrochemical treatment rendered the titanium alloy surface super-hydrophilic. Fibroblasts were seeded on the processed samples. After two weeks in culture medium, differences in the cell’s morphology and a reduced areal density were observed in the fs-laser treated regions. The two-step processing based on fs-laser structuring followed by electrochemical treatment appears as a powerful strategy for controlling cellular and bacterial adhesions on titanium alloys. Cardiologic applications for the surface functionalization of miniaturized (leadless) pacemakers are discussed.

Authors : A. S. Nikolov (1), E. Iordanova (2), G. Yankov (2), N. E. Stankova (1), K. Tz. Koev (1, 3), N. N. Nedyalkov (1), L. A. Avramov (1), D. B. Karashanova (4)
Affiliations : (1) Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria, (2) Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria, (3) Chair of Emergency Medicine, Department of Ophthalmology, Medical University  Sofia, 8 Bjalo More str., 1000 Sofia, Bulgaria, (4) Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences, Acad. G. Bonchev street, bl. 109, 1113 Sofia, Bulgaria;

Resume : Two different approaches are used to produce a colloid of Ag nanoparticles (AgNPs) with the purpose of application in ophthalmology. The requirements for such an application include most importantly a mono-dispersity of the colloid and the absence of NPs larger than 10 nm. The first approach consists of two-stages. First, a colloid is prepared using the fundamental wavelength (λ = 1064 nm) of a nanosecond Nd:YAG laser system of appropriate fluence and exposure time. The mean size of the NPs in the colloid obtained is slightly less than 10 nm, but there are ones of a larger size. In the second stage, this colloid is irradiated by an unfocused femtosecond laser beam of selected wavelength, energy and exposure time to reduce the nanoparticles size and modulate its distribution. The relevant changes of the colloid during the irradiation procedure are traced by the changes in the profile of its optical transmission spectrum. Histograms of the micrographs obtained by transmission electron microscopy illustrate the result obtained in regard to the mean size and the size distribution of the NPs. The second approach consists in fabricating the desired colloid directly by femtosecond laser ablation of suitable laser wavelength, fluence and laser exposure time. The structure of the fabricated nanoparticles is investigated by selected-area electron diffraction.

Authors : Yannick Bleu, Florent Bourquard, Anne-Sophie Loir, Christophe Donnet, Florence Garrelie
Affiliations : Université de Lyon, Université Jean Monnet-Saint-Etienne, CNRS, Institut d’Optique Graduate School, Laboratoire Hubert Curien UMR 5516, F-42023, SAINT-ETIENNE, France

Resume : This study reports the comparative investigation of graphene films prepared on Si (100) and SiO2 by combining pulsed laser deposition and rapid thermal annealing using Ni catalyst. The effect of substrate and growth temperatures (600-1000°C) on the formation of graphene films was investigated by Raman spectroscopy, mapping and scanning electron microscopy (SEM). It was found that graphene films formed on Si (100) is multilayered with the formation of various nickel silicides depending on the growth temperature, while graphene films prepared on SiO2 are predominant bi- and trilayered graphene with no nickel silicide formation. The analysis of the Raman D, G and 2D peaks intensities and positions as a function of the growth temperature showed a complete opposite evolution between Si (100) and SiO2 substrates. These findings contribute to a better understanding of the combination between the nature of the substrate and the growth temperature, when growing graphene films from solid carbon source with nickel catalyst on both Si (100) and SiO2 substrates. Such a good comprehension of the substrate impact is vital for potential applications and device fabrication of graphene.

Authors : Harim Oh, Minseok Seo, Jaeyong Kim, Junho Lee, Myeongkyu Lee*
Affiliations : Yonsei university

Resume : This article studies the effects of film and substrate on the laser-induced dewetting of metal thin films. Ag and Au films, both 10 nm in thickness, were deposited onto glass and Si substrates and dewetted using a single pulse from a nanosecond-pulsed Nd:YAG laser at  = 1,064 nm. The Ag film was completely dewetted into nanoparticles at a pulse energy density of about 70 mJ/cm2 on the glass substrate while an energy density over 390 mJ/cm2 was needed for the Si substrate. This is attributed to the fact that Si has a much higher thermal conductivity than glass and that the laser energy absorbed by the film significantly dissipated into the Si substrate rather than being solely used to heat the film. The Au film required slightly more laser energy in comparison to the Ag film. The energy densities of a laser pulse required to dewet the Ag and Au films were theoretically derived using one-dimensional heat conduction equations and thermodynamic data.The difference between the experimental and calculated pulse energies was more significant for the Si substrate. This indicates that lateral thermal diffusion occurred considerably on the Si substrate even with a nanosecond pulse duration. We demonstrate both experimentally and theoretically that as the thermal conductivity of the substrate increases, the film area dewettable by a laser pulse is decreased.

Authors : Harim Oh, Minseok Seo, Jaeyong Kim, Junho Lee, Myeongkyu Lee*
Affiliations : Yonsei university

Resume : Plasmonic color laser printing has several advantages over pigment-based technology, including the absence of ink and toner and the production of nonfading colors. However, the current printing method requires a template that should be prepared via nanofabrication processes, making it impractical for large-area color images. In this study, we show that laser-induced dewetting of metal thin films by a nanosecond pulsed laser can be effectively utilized for plasmonic color printing. Ag, Au, and their complex films deposited on a glass substrate were dewetted into different surface structures such as droplets, rods, and ripples, depending on the incident laser energy. The resulting morphological evolutions could be explained by Rayleigh and capillary instabilities. For a bimetallic film comprising Ag nanowires coated on an Au layer, a few different plasmonic colors were generated from a single sample simply by changing the laser fluence. This provides a possible method for implementing plasmonic color laser printing without using a pre-patterned template.

Authors : Alina Ilie 1, Monica Scarisoreanu 1, Claudiu Fleaca 1, Ana-Maria Banici 1 , Lavinia Gavrila-Florescu1, Elena Dutu 1, Florian Dumitrache 1, Valentin Teodorescu2, Anca Vasile3, Ioan Balint 3
Affiliations : 1 National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania\ 2 National Institute of Materials Physics, Magurele, Romania 3 Romanian Acad, Inst Phys Chem Ilie Murgulescu, 202 Spl Independentei, Bucharest 060021, Romania

Resume : The nano-TiO2 synthesis method along with W/V insertion, by means of metal doping or semiconductor coupling was found to promote the formation of specific crystalline phases, various nanoparticle morphologies, distinctive charge separation behaviours, wider spectral activity domains, improving finally the photocatalytic efficiency. TiO2 nanoparticles synthesized by laser pyrolysis have been proven to exhibit superior photocatalytic activity compared to commercial titania (P25 Degussa) or materials obtained by chemical synthesis methods. V/TiO2 and W/TiO2 composite nanoparticles obtained in one-step laser pyrolysis process, emerge as new photocatalysts for water treatment and hydrogen production applications. Further material development research allowed us to generate nanocomposites, combining the advantages of both nanomaterials, with controlled W:V:Ti atomic ratios. The synthesis parameters modulation, involving laser pyrolysis photo-excited processes of dissociation and nucleation, and use of injectors with specific geometry produces distinctive nanocomposite morphologies and characteristics, which influences carrier transport phenomena. X-ray diffraction (XRD), HR-TEM, EDS and BET techniques are used to explain the photocatalytic efficiency improvement as a consequence of crystalline phase composition, W/V concentration ratios and insertion type, nanoparticle size and morphology, stressing upon a comparative study regarding these types of nanocomposites.

Authors : A. Tiliakos1, C. Fleaca1, L. Gavrila-Florescu1, I.P. Morjan, A. Marinoiu2, E. Tanasa3, F. Dumitrache1
Affiliations : 1. National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., PO Box MG-36, Magurele, Ilfov, Romania 2. National Research and Development Institute for Cryogenic and Isotopic Technologies, ICSI Rm. Valcea, 4 Uzinei Street, Ramnicu Valcea, Valcea, Romania 3. Politehnica” University of Bucharest, Faculty of Applied Chemistry and Materials Sciences, 1-7 Gh. Polizu Str., Bucharest, Romania

Resume : Porous carbonic nanomaterials have been traditionally employed in the manufacturing of microporous layers (MPLs) and catalyst supports for polymer electrolyte membrane fuel cells (PEM-FCs), provided they present the material stability and flow management efficiency to secure adequate power densities. Aiming at obtaining nanocarbons at a competitive yield-to-cost ratio, laser pyrolysis has been established as a versatile method allowing for the bulk production of fine powders with uniform and controllable particle size distribution and morphology. The method applies high-power lasers on homogeneous gas-phase precursor mixtures of carbon and nitrogen donors to produce either pristine or nitrogen-doped core-shell nanocarbons, which are deposited on polymer electrolyte membranes for direct applications in PEM-FCs. However, since the electrocatalytic activity of both doped and undoped nanocarbons needs to be enhanced – especially targeting the sluggish oxygen reduction reaction (ORR) – we investigate appropriate protocols for seeding with platinum, the most commonly used precious metal catalyst for such purposes. Thus, simple deposition and pre-mixing protocols are investigated and compared to the more time-consuming chloroplatinic acid reduction route, with extensive characterization using spectrometric (Raman, XRD, XPS), thermogravimetric/adsorption (TGA, BET), and microscopy techniques (SEM, HRTEM), as well as performance evaluation on dedicated PEM-FC testing stations.

Authors : Strebezhev V.M., Yuriychuk I.М., Strebezhev V.V, Bondarenko D.V., Danigevych O.R.
Affiliations : Physical, Technical and Computer Sciences Institute, Yuriy Fedkovych Chernivtsi National University, Chernivtsi, Ukraine

Resume : The study of the structural transformations of Cd1-xМnxTe crystals surface after laser irradiation by millisecond and nanosecond pulses was carried out. A theoretical estimate of the surface temperature and the melting threshold of Cd1-xМnxTe crystals under the action of laser radiation with different wavelengths and pulse duration was made using solution of non-stationary thermal equation of heat transfer. An accordance between calculated dependence of the melting depth at different values of the laser energy density and experimental results of the thickness of the melted by the laser Cd1-xMnxTe layers has been obtained. When studying the laser treated surface of Cd1-xМnxTe crystals (x=0.1-0.45) in SEM at 30 kV, electron channeling images were obtained in the crystallographic contrast mode. The optimal values of the electron beam current, the diameter of the diaphragm and the angle of incline of the Cd1-xМnxTe samples in SEM which provide the maximum contrast of pseudo-Kikuchi lines were determined. The quality of the electron channeling images, the width and curvature of the lines on them, are compared with the laser processing modes and the structural perfection of the modified crystals surface. Data on the surface structure of Cd1-xМnxTe crystals at laser treatment in various modes - from the laser annealing to the laser melting and laser epitaxy have been systematized.

Authors : Fleaca C., Dumitrache F., Lungu I., Badoi A., Banita S.
Affiliations : NILPRP, Atomistilor 409, Magurele-Bucharest, Romania

Resume : Oxidic, metallic and/or carbidic iron-based magnetic nanoparticles synthesized by laser pyrolysis (starting from iron pentacarbonyl vapors) were mixed with natural aluminosilicate halloysite nanotubes and dispersed in water containing antibiotic drugs (neomycin sulfate or violamycin), later followed by the addition of sodium alginate biocompatible hydrophilic polymer. Using a syringe needle for the viscous mixture droplet generation, few mm monodisperse calcium alginate hydrogel composite beads were rapidly formed in contact with CaCl2 solution. The drug delivery capacity of these nanocomposites were tested in absence or in the presence of a high frequency magnetic field, showing accelerated release of antibiotic upon controlled local magnetic heating. The structure of the composites was analyzed sing SEM, FT-IR and XRD techniques, whereas the aqueous antibiotic concentration was quantified using UV-Vis spectroscopy.

Authors : A.F. Bonciu1,2, E. Sirjita1,2, S. Vizireanu1, G. Dinescu1, A. Palla-Papavlu1,*, M. Dinescu1
Affiliations : 1) National Institute for Lasers, Plasma and Radiation Physics, Magurele, Bucharest, 077125, Romania; 2) University of Bucharest, Faculty of Physics, RO 077125, Magurele, Romania *Corresponding author:

Resume : Attacks on national security of different European states as well as on the lives of their citizens have become a daily reality. Explosives and precursor materials are used in most of these attacks, which lead to the need for new detection solutions and technologies. Explosives are chemically unstable materials difficult to detect due to the low vapor pressure, therefore, novel devices and detection systems based on fully integrated arrays are of interest. In this work, we are focusing on fabricating sensor arrays based on chemiresistive sensors with proven sensing functionality for volatile organic compounds such as ammonia, acetone, and ethanol. The active materials in the sensor arrays are based on carbon nanowalls (CNW) and carbon nanowalls decorated with nanoparticles (SnO2). Vertical CNW synthesis is carried out by plasma-assisted chemical vapor deposition. The SnO2 decorated CNWs are obtained by spin coating the SnO2 nanoparticle suspension onto the already grown CNW films. For the fabrication of the sensor arrays, laser induced forward transfer (LIFT) is applied to transfer CNW and SnO2-CNW pixels onto metallic electrodes. The distribution of the CNWs and SnO2-CNW onto the metallic electrodes is investigated by scanning electron microscopy. Raman spectroscopy is used to check for any chemical modification in the transferred materials. Finally, the sensing characteristics, i.e. sensitivity, response and recovery times, selectivity are evaluated for both the CNW and SnO2-CNW based sensor arrays. It has been found that the SnO2-CNW arrays show a better sensitivity and a decreased recovery time (of approx. 20 seconds) than the CNW based sensor arrays. Following these results one can envision that active sensing materials based on CNWs and SnO2-CNW can be applied in explosive sensor arrays using lasers and plasma techniques. Acknowledgement Financial support from UEFISCDI, though the “Fabrication, calibration, and testing of advanced integrated sensor systems aiming at applications in societal security (TESTES)” project is gratefully acknowledged.

Authors : Amlan Das1, Andong Wang1, Mario Garcia-Lechuga1, Olivier Utéza1, Jan Siegel2, David Grojo1
Affiliations : 1Aix-Marseille Université, CNRS, LP3, UMR 7341-13288 Marseille, France; 2Laser Processing Group, Instituto de Optica, Consejo Superior de Investigaciones Científica (IO-CSIC), Serrano 121, 28006 Madrid, Spain

Resume : Focused ultrafast laser radiation can induce highly localized permanent changes in the structural and physical properties of silicon (Si) for the fabrication of microdevices in various fields. By using ultrashort pulses at infrared range (transparency domain of Si) a true 3D control is achieved by localized modifications at the surface as well as inside the samples. Among the control parameter, our work concentrates on variable pulse durations of 1.55 µm wavelength. In the experiments, we use an optical parametric amplifier pumped by a 180-fs laser system. A stretcher is developed to adjust the pulse duration between 200 fs and 20 ps. Irradiations on Si <100> wafers were performed by controlling the focusing conditions (high and low numerical aperture), energy and number of pulses. For 200-fs pulses, we observe a similar ability to ablate and/or amorphize the Si samples as reported in works using the usual wavelengths (e.g. 800 nm). However, the amorphization process benefits at 1.55 µm wavelength, resulting in amorphous layers thickness up to 50 nm. Using our longest pulses of 20 ps duration, we find that amorphization occurs only within a narrow energy window. In turn, we find it impossible to modify the bulk of silicon with 200 fs pulses but succeed to surpass the threshold for bulk modification with 20 ps pulses. These results provide an opportunity to explore the optimum pulse durations that enable laser silicon micromachining based on infrared pulses.

Authors : T. Dilova1, G. Atanasova1, A. Og. Dikovska2, N. N. Nedyalkov2
Affiliations : 1Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 11, 1113 Sofia, Bulgaria; 2Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, Sofia 1784, Bulgaria

Resume : Highly porous pure and noble-metal (Pd, Ag, Pd-Ag) doped ZnO nanostructures were fabricated by PLD in open air in view of ammonia sensor application. The technology used for sensors fabrication leads to the formation of nanostructures composed by nanoparticles or nanoaggregates. These nanostructures possess a large surface-to-volume ratio, which makes them suitable for gas-sensor application. In this work, we demonstrated an enhanced response of the nanocomposite sensors to ammonia exposure. The effect was investigated of the light irradiation on the response and time of response and recovery of the sensor elements. The gas sensing properties of the samples were compared under light irradiation with different wavelengths. The irradiation of the sensors surface by visible light raised the rate of desorption of the gas molecules at room temperature. As a result, the irradiation by blue light substantially changed the time of recovery of the sensor. A higher response and a faster recovery of the sensor were registered when the sensor was illuminated by red light. The illumination of the sensor surface by white light increased the sensor response, which is probably due to the UV component in the white light spectrum. Acknowledgments The authors acknowledge the financial support by project DM19/2 “Noble metal doped ZnO nanostructures for optimal gas-sensing properties upon light irradiation” under the „Competition for financial support for project of junior researchers and postdocs – 2017” Program of the National Science Fund, Ministry of Education and Science of Bulgaria.

Authors : D. Chioibasu, A. C. Popescu
Affiliations : Center for Advanced Laser Technologies - CETAL, National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania

Resume : Ti6Al4V cranial prostheses in form of patterned meshes were laser 3D printed by Selective Laser Sintering in argon environment, using a CO2 laser source and micronic Ti6Al4V powder as starting material. The size and shape of prostheses were chosen based on actual computer tomography images of patient skull fractures supplied in the framework of a collaboration with a neurosurgery clinic. After optimizations of scanning speed and laser parameters, the printed material was defects free as shown by metallographic analyses and chemically it was uniform, without elemental segregation or depletion, as revealed by electron diffraction X-ray spectroscopy. The bulk had an α’ martensitic metallographic structure with randomly oriented acicular grains. The prostheses produced by 3D printing were further coated by Magnetron Sputtering with a bioactive thin layer of a natural animal origin hydroxyapatite, obtained from calcination of bovine bones. The X ray diffraction structural investigations of films revealed a monophasic hexagonal hydroxyapatite phase. Degradation tests demonstrated the biomineralization capacity of the films and resistance to degradation in biomimetic environments. In vitro tests were conducted in order to test the natural apatite bioactivity. Osteoblast cells proliferated from 1-7 days, they extended over the substrate in order to maximize surface contact and emitted pseudopodes, to the difference of cells grown on borosilicate control glass that kept a polyhedral shape.

Authors : Joo Yeon Kim1*, Seung-Yeol Lee2, Chi Young Hwang1, Sanghoon Cheon1, SeongMok Cho1, Tae Youb Kim1and Chi-Sun Hwang1
Affiliations : 1Reality Display Research Section, Electronics and Telecommunications Research Institute (ETRI), Daejeon 34129, Korea 2School of Electronics Engineering, Kyungpook National University, Buk-gu, Daegu 41566, Korea

Resume : A hologram is a three-dimensional (3D) image created by the interference pattern formed when a light source (the reference beam) of fixed wavelength encounters light of the same fixed wavelength arriving from an object (the object beam). The wavefronts of light from the original object is recreated by the diffraction pattern when it is illuminated by the reference beam only. In order to create the diffractive pattern, computer generated hologram(CGH) is introduced for utilizing the wave theory of light to represent both the object and reference waves mathematically, which is implemented using Matlab. Based on the Fraunhofer diffraction formula, the Fourier Transform operation is used to give the far field amplitude calculation required for simulating the interference pattern. Therefore, in this case, CGH do not require actual objects to generate the hologram as long as the light scattered or diffracted off the object could be represented mathematically. Since the first CGHs were invented by Brown and Lohmann [2], CGHs are finding widespread application especially in in fabricating micro-/nano-optical structures as optical components for security and authentication because of complicated non-existing spatial images reconstructed by diffraction. In this work, the simple preparation method of polymer-imprinted CGHs is introduced for security applications, which can be considered in terms of “easy fabrication way for mass production” with an appreciate time and cost-efficient effect.

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Pulsed laser deposition : Maria Dinescu
Authors : Guus Rijnders
Affiliations : MESA+ Institute for Nanotechnology, University of Twente, POBox 217, 7500AE, Enschede, The Netherlands

Resume : In recent years, it has been shown that novel functionalities can be achieved in oxide heterostructures in which the interfaces are atomically controlled, in terms of atomic stacking as well as in terms of the local symmetry. In transition metal perovskites ABO3, the physical properties are largely driven by the rotations of the BO6 octahedra, which can be tuned in thin films through strain and dimensionality control. However, both approaches have fundamental and practical limitations due to discrete and indirect variations in bond angles, bond lengths, and film symmetry by using commercially available substrates. We introduced modulation tilt control as an approach to tune the ground state of perovskite oxide thin films by acting explicitly on the oxygen octahedra rotation modes-that is, directly on the bond angles. By intercalating the prototype SmNiO3 target material with a tilt-control layer, we cause the system to change the natural amplitude of a given rotation mode without affecting the interactions. With this approach, we successfully adjusted the metal-insulator transition (MIT) to room temperature to fulfil the desired conditions for optical switching applications. In this contribution, I will highlight the recent developments in atomic controlled growth of epitaxial oxides by pulsed laser deposition and discuss recent new insights in the “physics” of pulsed laser deposition of complex oxides, focusing on the influence of oxygen pressure on the deposited species during growth as well as the large scale growth of epitaxial oxides on wafers up to 200 mm in diameter.

Authors : Ch.Nicolaou1a, A. Zacharia2, A. Delimitis3, G. Itskos2, and J. Giapintzakis1b
Affiliations : 1 Department of Mechanical and Manufacturing Engineering, University of Cyprus, 75 Kallipoleos Av., PO Box 20537, 1678 Nicosia, Cyprus; 2 Experimental Condensed Matter Physics Lab, Department of Physics, University of Cyprus, 75 Kallipoleos Av., PO Box 20537, 1678 Nicosia, Cyprus; 3 Department of Mechanical and Structural Enginering and Materials Science, University of Stavanger, N-4036 Stavanger, Norway

Resume : Cu(In,Ga)Se2 (CIGS) thin-film solar cells have been extensively studied by the research community and industry, motivated by the high conversion efficiencies, high radiation resistance, remarkable stability and the potential of lower cost production compared to crystaline silicon solar cells. The evolution of the efficiency reported through the years is notable, with record performances of 22.9%. The recent improvement in cell efficiency paves the way for module efficiencies up to 18% over the next few years. The typical CIGS solar cell with efficiency above 20% has the following configuration: soda-lime glass (SLG) as substrate, sputtered Mo as back contact, multi-stage co-evaporated CIGS as p-type absorber, chemical bath deposited CdS as n-type buffer layer and sputtered i-ZnO/ZnO:Al bilayer as the transparent front contact. Many deposition methods are being utilized to grow CIGS and CdS thin films; however, only few works on the pulsed laser deposition (PLD) technique have been reported. In this presentation, the growth of CdS/CuIn0.7Ga0.3Se2/Mo multi-layer structures on soda-lime glass (SLG) using PLD will be presented. The influence of PLD parameters on the properties of the CIGS and CdS layers and also the CdS/CIGS/Mo heterointerfaces will be discussed. Complete structural, compositional and morphological characterization, along with electrical and optical measurements, will be used to evaluate the quality of the CdS/CIGS diode and identify the optimum PLD growth conditions of the multi-layer structure.

Authors : Yannick Bleu (1), Florent Bourquard (1), Vincent Barnier (2), Anne-Sophie Loir (1), Florence Garrelie (1), Christophe Donnet (1)
Affiliations : (1) Université de Lyon, Université Jean Monnet-Saint-Étienne, CNRS, Institut d’Optique Graduate School, Laboratoire Hubert Curien UMR 5516, F-42023, Saint-Étienne, France ; (2) Mines Saint-Etienne, Univ Lyon, CNRS, UMR 5307 LGF, Centre SMS, F - 42023 Saint-Étienne France

Resume : The introduction of dopants, such as boron, into the graphene network, is essential for many applications (electrochemistry, sensors, photovoltaics, catalysis, etc.). Many preparation routes have been investigated for B-doped graphene (BG) films: CVD, chemical reactions between graphene or graphene oxide with boron precursors, hydrothermal and solvothermal processes, arc discharge, high temperature sublimation of highly B-doped SiC and B4C thermal decomposition. Another way consists in pulsed laser co-ablation of C and B solid sources followed by rapid thermal heating of the B-doped carbon film deposited on a metal catalyst, to obtain BG layers. The objective is to achieve a better control of boron concentration in the films. Here, we use for the first time pulsed laser co-ablation for the synthesis of B-doped graphene layers. Amorphous a-C:B films, containing 2%at. boron, 10 nm thick, are synthetized by nanosecond pulsed laser deposition on a Ni thin film (60 nm thick) previously deposited on a SiO2 substrate. Rapid Thermal Annealing is performed at 1100°C during 2’ with a heating rate of 15°C/s and a cooling rate of 1°C/s. Raman, XPS, FEG-SEM and AFM characterizations allow to determine the nature, composition and morphology of the BG films. The results confirm the fabrication of bi-trilayers boron doped graphene films with the same boron doping level (2%at) as the starting material. Our results pave a new way for boron doped graphene synthesis using laser processing.

Authors : Cristian Ursu, Bogdan George Rusu, Mihaela Olaru, Petru Edward Nica, Cristian Focsa
Affiliations : Laboratory of Polymeric Materials Physics, “Petru Poni” Institute of Macromolecular Chemistry, 41 A Gr. Ghica Voda Alley, Iasi 700487, Romania; Department of Physics, “Gheorghe Asachi” Technical University, Iasi, 700050, Romania; Univ. Lille, CNRS, UMR 8523, PhLAM – Physique des Lasers, Atomes et Molécules, CERLA – Centre d’Etudes et de Recherches Lasers et Applications, F-59000 Lille, France

Resume : A V-shape radiating carbon plasma, generated through excimer laser ablation of graphite, was characterized by complementary techniques. Fast ICCD imaging along with time- and space- resolved OES was used to sequentially record the evolution of plasma as a whole, or of specific excited species, while Faraday cup measurements provided the space-time distribution of the ions. To complete the picture, mechanical profilometry brought results on laser created craters features, that correlate with the plasma properties. When expanding in vacuum, the V-shape plasma consists in two radiating arms (so arranged that they form a sharp angle) and a low emission central region made of fast particles. Besides its unusual shape, a peculiar feature of the V-shape carbon plasma is the enhanced emitting area of visible radiation from C2 molecules. Moreover, along the plasma central axis, a minimum of emission intensity of the optically excited species was observed, while the ion distribution function reveals a maximum. Increasing the working pressure, the fast central plasma structure is better evidenced, through a re-heating effect of the ambient gas. In this context, the expansion velocities of the V-shape plasma structures and different parameters (electron density and plasma temperature) were determined.

09:45 Coffee break    
Authors : M.O. Cernaianu*, P. Ghenuche*, D. Ursescu*, Y. Hayashi**, H. Habara**, F. Negoita*, D. Stutman* and K. A. Tanaka*
Affiliations : * - Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH) – Extreme Light Infrastructure – Nuclear Physics (ELI-NP), Bucharest-Magurele, Romania ** - Graduate School of Engineering, Osaka University, Osaka, Japan

Resume : In high power laser experiments where intensities lie in the range of 10^21-10^23 W/cm^2, having a high contrast ratio of the temporal profile and protecting the expensive laser optics from plasma debris and laser back reflections represent critical issues. The first is necessary in order to perform experiments with ultra-thin film targets and exploit advanced acceleration mechanisms while the second is required to ensure the safe operation of the laser system and increase optics lifetime. During the laser – matter interaction, the laser light intensity can deform and modulate the target, with the reflected light travelling back and potentially damaging the laser system and the transport optics. Typically, plasma mirrors are used to increase the temporal contrast of the laser with up to two orders of magnitude per mirror. The talk introduces the plasma mirrors physics and their use for contrast enhancement and protection from laser back – reflections.

Authors : E. Soria [1,2], A. Mariscal [1], J. Gonzalo [1], R. Serna [1], M. Iriarte [1]
Affiliations : [1] Laser Processing Group, Instituto de Optica, IO-CSIC, Serrano 121, 28006 Madrid, Spain; [2] SAFTRA Photonics, Jesenná 5, 040 01 Ko?ice Slovakia.

Resume : Recently fluorescence-based techniques have gained great attention for detection of organic substances in small quantities for applications in environment control and health. Photonic technologies are in an excellent position to provide solutions in this context, since devices based on optical monitoring of light properties are very powerful tools for remote and non-invasive sensing applications. For these applications are necessary bright emitters that are clearly distinguishable and with a stable emission. In this respect rare-earth ions are very robust emitters with a very clean, narrow and robust emission. However, their emission tends to be less bright than that of traditional dyes due to their characteristic long-lifetime. A possible solution would be their combination with metallic nanostructures, particularly of Au and Ag, as they provide an enhanced emission due to plasmonic field absorption enhancement. In this work we investigate the modification of the emission luminescence properties of active thin films of europium oxide (Eu2O3) deposited on top of self-organized Au or Ag nanostructures prepared by Pulsed Laser Deposition (PLD). Au is investigated for its great stability for biological applications, while Ag is investigated due to the narrower band of its plasmon and its higher scattering efficiency. The potential enhancement of the emission efficiency is studied as a function of the deposition conditions, thickness and post-annealing treatments of Eu2O3 films.

11:15 Plenary Session 1    
12:30 Lunch    
Laser interactions with soft materials and biological applications : Johannes Pedarnig
Authors : T. Venkatesan*, Sreetosh Goswami*, Li Changjian*, Chen Jingsheng*, Abhijeet Patra*, Viknish Krishnan Kutty* and Sreebrata Goswami**
Affiliations : * NUSNNI, T-Labs Building, National University of Singapore, Singapore 117411 **Association for Cultivation of Sciences, Jadavpur Kolkata, India 700032

Resume : Abstract Artificial intelligence (AI) has been heralded as the flagbearer of the fourth industrial revolution. But it comes with a cost and that is computing power. It is projected that by 2040, we will need more computing energy than the total terrestrial energy. Memory devices are responsible for a significant fraction of the energy consumed in electronic systems- typically 25% in a laptop and 50% in a server station. Reducing the energy consumption in memories is an important goal. For the evolving field of artificial intelligence the compatible devices must simulate a neuron in order to meet the low energy required for brain-like functions. We are working on three different approaches towards these problems- one involving an organic metal centred azo complex, the other involving oxide based ferroelectric tunnel junctions and the last involving real live neuronal circuits. Experimental Results Organic Approach: Our organic resistive memories built on oxide surfaces are robust, stable (operating from -40 to 80C for >10^6s) and enduring (>10^12 cycles) exceeding the ITRS roadmap specification significantly demonstrating the viability of this system for practical applications [1]. The molecule is a Ru centred Azo ligand based complex. The azo group can have three charged (redox) states and these molecules are spin coated on a PLD deposited atomically flat ITO film with metal electrodes on top. Besides meeting industrial metrices, this work implements in-situ spectroscopic platforms to detect molecular states of devices while in operation - an elusive goal in organic electronics. The mechanistic understanding thus developed leads to the realization of several hitherto unforeseen scientific paradigms such as voltage-controlled charge disproportionation, sequential layered redox mechanism leading to even 29-state devices. Such devices can offer a boon to the neuromorphic technology and brain inspired computing which are still in search of ideal material candidates for neuromorphic devices. Our devices are scalable from micron size to 50nm2 (measured with a c-AFM tip). With scaling the switching voltage drops from a maximum of 4 Volts (in a micron device) to 120mV (to a nano-device). The nano structures act as seeding points of locally enhanced fields significantly lowering the charge injection barrier. With these devices, we are now able to reach100aJ switching energy, at least 4 orders superior to any other resistive memory. Oxide Approach: On the oxide front the significant results are that ferroelectricity is seen even in PLD MBE grown one or two atomic layers of BaTiO3 or BiFeO3 resulting in ferroelectric tunnel junctions with usable On/Off ratios [2-5]. Oxygen vacancy motion can also play an important role in changing the device characteristics leading to synaptic characteristics and lead to multiple memory states. Live Neuronal circuits: Last but not the least, combinatorial PLD based oxide surfaces can be utilized to force neurons to grow at specific places on a surface giving the potential for fabricating live neuronal circuits. Using lithographically etched channels the axons could be guided to create a 2D matrix of neurons and if such circuits could be made reproducibly with live neurons this would lead to a significant understanding of neuronal communications and also understanding neurodegeneration process and also developing drugs to combat neurodegeneration. References 1. Sreetosh Goswami, et al., Nature Materials, 16, 1216 (2017) 2. C. J. Li, et al., Nano Letters 15 (4) 2568–2573 (2015) 3. Han Wanget al., Nature Comm. 9, 3319 (2018) 4. Weiming Lü, et al., Advanced Materials - In Print 5. Rui Guo, et al., ACS Applied Materials and Interfaces, 10, 12862 (2018)

Authors : L. Duta1, M.C. Chifiriuc2,3, G.E Stan4, F.N. Oktar5,6, V. Craciun1
Affiliations : 1National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania 2Department of Microbiology, Faculty of Biology, University of Bucharest, Bucharest, Romania 3Research Institute of the University of Bucharest (ICUB), Earth, Environmental and Life Sciences Division, Bucharest, Romania 4National Institute of Materials Physics, Magurele, Romania 5Department of Bioengineering, Faculty of Engineering, University of Marmara, Istanbul, Turkey 6Advanced Nanomaterials Research Laboratory (ANRL), University of Marmara, Istanbul, Turkey

Resume : Simple and doped biological-origin hydroxyapatite films were synthesized by Pulsed Laser Deposition onto medical grade Ti substrates. The role of doping reagents on physical-chemical, mechanical and biological properties of structures was studied. Morphological examination evidenced the fabrication of rough surfaces, ideal for the good adhesion of cells and anchorage of implants in situ. Structural investigations demonstrated a monophasic apatite-like nature of synthesized structures. Compositional analyses revealed the presence of typical natural doping elements of bone, along with a quasi-stoichiometric target-to-substrate transfer. Inferred bonding strength values were higher than the threshold imposed by ISO standard regulating load-bearing implant coatings. After only three days of immersion in simulated body fluid, FTIR spectra showed a remarkable growth of a biomimetic apatitic layer, indicative of a high biomineralization capacity of coatings. Synthesized layers exhibited low cytotoxicity on human osteosarcoma and skin cells and therefore, an excellent biocompatibility, corroborated with a long-lasting anti-staphylococcal and –fungal biofilm activity. Along with low fabrication costs, these combined characteristics could offer guidance towards the suitability of using biological-derived materials as viable alternatives to synthetic HA for the fabrication of a new generation of implant coatings. Acknowledgements: Contract PD 6/2018 and Core Programme 3N/2018.

Authors : Ehud Greenberg, Nina Armon , Hagay Shpaisman
Affiliations : Department of Chemistry and Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 5290002, Israel

Resume : The laser-induced microbubble technique (LIMBT) has been developed recently for micro-patterning of various materials. In this method, a laser beam is focused on a dispersion of nanoparticles (NPs), leading to the formation of a microbubble due to laser heating. Convection currents around the microbubble carry NPs that are then pinned to the bubble/substrate interface. Moving the focused beam results in migration of the microbubble and the deposition of material at the bubble/substrate contact area. We have recently found that controlling the construction and destruction of the microbubble, through modulation of the laser, enables the formation of continuous patterns by preventing the microbubble from being pinned to the deposited material.[1] Moreover, we show that a similar mechanism could explain microstructure formation from an ion solution. Photo-thermal reduction leads to formation of NPs that are then pinned to the bubble/substrate interface. By analyzing the nanostructure of the deposits by TEM, we show that the deposition on the substrate is a combination of amorphous and crystalline moieties. This innovative approach can be applicable for producing thin conductive patterns and allow fabrication of electronic devices and sensors. 1. Armon, N. et al. Continuous Nanoparticle Assembly by a Modulated Photo-Induced Microbubble for Fabrication of Micrometric Conductive Patterns. ACS Appl. Mater. Interfaces 9, 44214–44221 (2017).

Authors : E. Gutiérrez1, I. Gabaldón2, M.C. García-Gutiérrez1, A. Nogales1, A. Rodríguez-Rodríguez1, A. Cirera2, A. Varea2, A. Vilà2, T.A. Ezquerra1, E. Rebollar3
Affiliations : 1Instituto Estructura de la Materia (IEM-CSIC), Serrano 121, 28006 Madrid, Spain; 2Departament d’Enginyeries: Electrònica, IN2UB-Universitat de Barcelona, 08028 Barcelona, Spain; 3Instituto de Química-Física Rocasolano (IQFR-CSIC), Serrano 119, 28006 Madrid, Spain

Resume : There is still a widespread interest in conducting polymers due to their potential applicability in organic solar cells, organic field-effect transistors and organic light-emitting diodes just to cite a few examples. Among the conducting polymers, poly(3,4-ethylenedioxythiophene) complexed with poly(styrenesulfonate) (PEDOT:PSS) presents a series of interesting properties gaining importance since, besides its conductivity, it is transparent in the visible region, soluble in water, thermally stable and flexible. In this work, PEDOT:PSS thin films have been irradiated under ambient conditions with the 4th harmonic of a Nd:YAG laser resulting in Laser Induced Periodic Surface Structures (LIPSS) parallel to the laser polarization with a period close to the laser wavelength. Shape and size of LIPSS can be characterized by Atomic Force Microscopy (AFM). The nanoscopic structure of PEDOT:PSS films before and after irradiation have been studied by Grazing-Incidence Wide-Angle X-Ray Scattering (GIWAXS) using synchrotron radiation. In order to analyze the impact of laser treatment on the electrical properties of PEDOT:PSS, conductive AFM (C-AFM) measurements have been performed, showing that LIPSS preserve electrical conductivity of PEDOT:PSS. These results are important regarding the possibility of achieving functional polymer nanostructures by a quick and reproducible approach.

Authors : Martin Ehrhardt1, Shengying Lai1,2, Pierre Lorenz1, Joachim Zajadacz1, Bing Han3, Klaus Zimmer1*
Affiliations : 1 Leibniz Institute of Surface Engineering (IOM); Leipzig 04318, Germany 2 School of Science; Nanjing University of Science & Technology; Nanjing 210094, P.R. China 3 Advanced Launching Co-innovation Center; Nanjing University of Science & Technology, Nanjing 210094, P.R. China *E-mail:

Resume : Submicron pattern fabrication by laser direct writing is still challenging due to the required resolution of the optics required for these pattern sizes. Therefore, various approaches of submicron pattern formation by bottom up processes such as laser-induced self-organizing processes, which allow submicron structure fabrication with dimensions equal or below the wavelength of the laser light, are under investigation. Here, the combination of two processing steps for the fabrication of hierarchical pattern is presented. Pre-patterned polymer substrates that feature polymer structures with micron dimensions are irradiated with pulsed UV laser radiation with a wavelength of 248 nm and a pulse duration of ~25 ns at low repetition rates. In consequence of this laser irradiation, laser-induced periodic surface structures (LIPSS) are formed at the surface of the pre-patterned polymer and allowing hierarchical pattern fabrication comprising micron and submicron features. Within the presentation the impact of the laser irradiation parameters such as laser fluence, repetition rate, spot size and confinement of the irradiation to the characteristics of the achievable LIPSS on top of the pre-patterned substrates are shown. In addition the geometry of the LIPSS for different dimensions and shapes of the pre-patterns is shown. The potential processes involved in the formation process of the hierarchical pattern will be discussed.

15:30 Coffee break    
Authors : Ryo Matsumura, Wipakorn Jevasuwan, Naoki Fukata
Affiliations : International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS)

Resume : To realize next generation thin-film devices and/or 3D-LSIs, growth of polycrystalline Ge and/or GeSn thin films on insulating substrates is essential. Here, we have investigated CW laser annealing method to fulfill this demand. In the experiment, amorphous Ge (a-Ge) films or a-GeSn films with Sn concentration of 17% were firstly deposited on quartz substrates. Laser lights (diameter: ~10 um, wavelength: 532 nm) were irradiated on the samples with scanning speed of 6.67 m/s. Here, CW Nd:YVO4 diode-pumped-solid state laser was used as the laser source, and the laser power was changed from 350 to 1200 mW. Nomarski microscopy and Raman spectroscopy supported that both Ge and GeSn films were successfully crystallized after laser irradiation. Interestingly, crystallinity of GeSn film showed strong dependence on annealing laser power, while that of Ge film showed little dependence. We speculate that this is due to the difference of crystallization phenomena. The details will be discussed on site.

Authors : Karima Tabakkouht, Mohamed Oujja, Mikel Sanz, Esther Rebollar, María Sánchez-Arenillas, J. F. Marco, Marta Castillejo, Rebeca de Nalda
Affiliations : Instituto de Química Física Rocasoalno, Consejo Superior de Investigaciones Científicas, C/ Serrano 119, 28006 Madrid

Resume : Silicon carbide (SiC) has attracted much attention in the last years due to its excellent physical and electrical properties, such as wide bandgap, high thermal conductivity, high breakdown electric field, high saturated electron drift velocity and resistance to chemical attack. These properties make SiC a promising material for high-temperature, high-power and high-frequency electronic devices as well as for optoelectronic such as solar cells, image sensors, gas sensors and photodiodes, just to cite a few. Thin films of SiC on Si (100) and SrTiO3 (100) substrates were grown by nanosecond pulsed laser deposition (PLD) at the wavelengths of 1064, 532 and 266 nm using a Q-switched Nd:YAG laser. Upon irradiation for two hours at a repetition rate of 10 Hz and a distance target-substrate of 4 cm, deposits consisted of smooth and uniform layers, holes and cracks free, with average roughness ≤ 1 nm and with 20 to 100 nm thicknesses as determined by atomic force microscopy in tapping mode. The effect of laser irradiation wavelength, laser fluence and the temperature of the substrate (300 K vs. 1025 K) on the morphology, composition and crystallinity of the deposits was determined. Deposits were analyzed by X-ray diffraction, micro-Raman spectroscopy and X-ray photoelectron spectroscopy to characterize their crystallinity and composition. Additionally, the nanomechanical properties of the deposited films and the photoluminescence were evaluated.

Authors : I. Boerasu1, R. Birjega1, N.D. Scarisoreanu1, M. Dinescu1, N. Enea1, V. Ion1, V. Leca2
Affiliations : 1National Institute for Laser, Plasma and Radiation Physics, Magurele, Romania; 2 Extreme Light Infrastructure - Nuclear Physics, Horia Hulubei National Institute for Physics and Nuclear Engineering, Magurele, Ilfov, Romania

Resume : Herein, we report about an anomalous behavior of the photoelectrochemical (PEC) response of Eu-doped BiFeO3 (BEFO) thin films, as a function of the film’s thickness. The aim of the study was to reveal the water splitting potential of doped BFO with rare-earth Eu element. Heterojunction composed of Eu-BiFeO3 and Nb-SrTiO3 (STON) single crystal substrates were fabricated via pulsed laser deposition technique (PLD). By X-ray diffraction, the crystal structures of all deposited thin films were identified as rhombohedral one, with the out-of-plane axis value as a function of film’s thickness. Optical absorption measurements were carried out for the grown films, an indirect and direct band gaps being identified, with the values for both types of bend-gaps depending on the epitaxial strain. The photoelectrochemical behavior (PEC) was analyzed in respect with the thickness of the deposited BEFO layer. To investigate the PEC performance of the fabricated heterojunctions, the photocurrent density ( Jph ) versus bias potential characteristics in-electrolyte PEC setups has been measured. We have found that the photoelectrochemical response was higher for the BEFO samples as compare with the undoped BFO ones. Moreover, the photocurrent density ( Jph ) is almost independent by the film thickness is ranging from 20 nm to 200 nm, while a significant higher photoelectrochemical response is characterizing the heterojunction based on a 180-200 nm thick BEFO films. These anomalous photoelectrochemical response behavior were analyzed in conjunction with the HR-SEM and scanning electron microscopy (SEM) - room-temperature cathodoluminescence (CL) surface imaging analysis.

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Laser ablation in liquids and nanoparticles formation : Stephan Barcikowski
Authors : David Amans (1), Tim Hupfeld (2), Gaétan Laurens (1), Samy Merabia (1), Stephan Barcikowski (2), and Bilal Gökce (2)
Affiliations : 1- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Lyon, France 2- Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Universitaetsstrasse 7, 45141 Essen, Germany

Resume : Producing colloids through laser ablation in liquid (LAL) has become a popular technique. LAL is scalable, economically viable, and a large variety of materials are accessible. LAL works in a one-step process and, as a consequence, LAL performed in oils or monomers has a high potential for additive manufacturing, or nanoparticle-polymer composites manufacturing. Energy deposition on a target immersed in a liquid with a nanosecond pulse leads to a confined laser-induced plasma, quickly quenched after a few microseconds, and then to a vapour bubble containing nanoparticles, which collapses after a few hundreds of microseconds. LAL has been extensively studied when performed in standard solvents, but not in viscous liquids. It is still mostly unknown how viscosity and surface tension influence the bubble dynamics (shape, size, lifetime), and then nanoparticles maturation inside the bubble. By investigating laser-induced bubbles as a function of the liquid viscosity, using an ultrafast shadowgraph imaging setup, we give a deeper insight into what determines the bubble dynamics. We showed that in highly viscous polyolefin, the bubble shape diverges from the semi-spherical shape usually observed: an increase in the viscosity and hereby in the capillary number Ca results in the appearance of a hysteresis between expanding and shrinking bubble. Moreover, laser-induced bubble formation leads to a large Ca number, which corresponds to a case poorly described in literature.

Authors : A. De Bonis, A. Galasso, A. Santagata, R. Teghil
Affiliations : A. De Bonis; A. Galasso; R. Teghil Dipartimento di Scienze, Università della Basilicata, Potenza, Italy A. Santagata UOS Potenza, CNR-ISM, Tito Scalo (PZ), Italy

Resume : Laser ablation of metal-transition solid targets in organic solvents is a versatile strategy to synthesize metal carbide and carbon encapsulated metal nanoparticles that are obtained by mechano-chemical synthesis, requiring severe experimental conditions, usually. The formation of MxCy and core/shell MC/M@C nanostructures has been studied during the ablation of Ti, Ta and Mo metallic targets in organic solvents with different C/H and C/O ratio. Ablation experiments have been carried out by two laser sources (Nd:YAG, 532nm, 7nm, 10Hz and Nd: glass, 527nm, 250fs, 10Hz) to highlight the effect of laser pulse duration on properties and composition of the obtained nanostructures. The synthesized materials have been characterized by microscopic (SEM, TEM and AFM) and spectroscopic (FTIR, microRaman and XPS) techniques. The several reactions involved during the ablation process determine nanostructures composition, that has been related to the reactivity and physico-chemical properties both of the ablated targets both of the liquid media.

Authors : A.Tymoczko1, M. Kamp2, C. Rehbock1, U.Schürmann2, O. Prymak1, L. Kienle2, S. Barcikowski1,
Affiliations : 1 University of Duisburg-Essen, Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE), Universitätsstr. 7, 45141 Essen, Germany 2 University of Kiel, Technical Department, Synthesis and Real structure, TEM- Centrum, Kaiserstr. 2, 24143 Kiel

Resume : Iron-gold core-shell (CS) nanoparticles (NPs) are interesting as they allow the combination of properties such as nanomagnetism, plasmonics and thiol-based conjugation chemistry in one particle1. Laser ablation in liquids (LAL) is a versatile technique which allows generation of these CS NPs in a one step process directly from alloy bulk targets2. However, CS formation by LAL is still limited, due to a competitive process generating metastable solid solution (SS) NPs as by-products3. Therefore, the main focus of our work lies in a detailed understanding of the formation mechanism of the FeAu NPs by LAL and in this context deduce process parameters, which allow a maximum in CS yield. The internal phase structure of the resulting particles is analyzed by X-Ray diffraction (XRD) and High Resolution Transmission Electron Microscopy (HR-TEM). The results indicate that primarily the target composition as well as the nanoparticle size critically influence the CS/SS ratios, while high CS yields were found when iron molar fractions in the target exceed 65% and particle diameters are bigger than 10 nm. The experimentally found size effect was confirmed by theoretical calculations which revealed that the lowest free Gibbs Energy, indicating the thermodynamically most stable morphology, was found for a Fe@Au core shell-structure in case of particle sizes > 10 nm. These results can open the way towards high yield one step green Fe-Au CS NPs synthesis based on laser ablation in liquids. [1] T. A Larson, J. Bankson, J. Aaron, K. Sokolov, Nanotechnol., 2007, 18, 325101. [2] P. Wagener, J. Jakobi, C. Rehbock, V. S. K. Chakravadhanula, C Thede, U. Wiedwald, M. Bartsch, L. Kienle, S. Barcikowski, Sci. Rep., 2016, 6, 23352. [3] A. Tymoczko, M. Kamp, O. Prymak, C. Rehbock, J. Jakobi, U. Schürmann, L. Kienle, S. Barcikowski, Nanoscale, 2018, 10, 16434-16437.

Authors : Bilal Gökce, Tim Hupfeld, René Streubel, Michael Schmidt, Johannes Henrich Schleifenbaum, Stephan Barcikowski
Affiliations : Technical Chemistry I, University of Duisburg-Essen, Germany; Technical Chemistry I, University of Duisburg-Essen, Germany; Technical Chemistry I, University of Duisburg-Essen, Germany; Department of Photonic Technologies, University of Erlangen-Nuremberg, Germany; Digital Additive Production, RWTH Aachen University, Germany; Technical Chemistry I, University of Duisburg-Essen, Germany;

Resume : Powder material development is crucial for laser-based additive manufacturing (LAM). Within the DFG Priority Program SPP2122 “Materials for Additive Manufacturing” we develop new composite materials with nanoparticles to overcome this limitation. These nanoparticles are generated by laser synthesis and processing of colloids (LSPC), a method that has been established as an economically feasible method to synthesize clean and surfactant-free colloidal nanoparticles in the gram-scale. To produce new compounds for powder-based LAM, laser-generated colloidal nanoparticles are adsorbed on metal or polymer powders through pH-variation under consideration of colloidal stability to avoid agglomeration. Due to the barrier-free surface of the small, highly dispersed colloidal nanoparticles, a high surface coverage and dispersion can be achieved even with mass loadings of 0.1 wt%, as will be shown in the contribution for silver nanoparticles supported on polyamide 12 powder or yttrium oxide nanoparticles supported on steel powder. Studies on LAM-built parts also show that the homogeneity of the surface coverage as well as the dispersion of the nanoparticles can be transferred to the final part. Within the additively manufactured metal component, we further show that the particle spacing of Y2O3 inclusion can be adjusted by the initial mass fraction of the adsorbed Y2O3 particles on the micropowder which finally leads to a significant increase in the compressibility at high temperatures.

09:45 Coffee break    
Authors : Alfred Vogel, Xiao-Xuan Liang, Sebastian Freidank, and Norbert Linz
Affiliations : University of Lübeck

Resume : We review nonlinear energy deposition by tightly focused laser pulses into water and the subsequent hydrodynamic events, with water representing large-band-gap materials. Tight focusing avoids nonlinear beam propagation effects and ensures spherical shock wave emission and bubble dynamics. The investigated parameter space encompasses pulse durations from fs to ns, wavelengths from UV to IR, and pulse energies from the bubble threshold to high-density plasmas far above threshold. We address the points: 1. Nonlinear energy deposition and plasma formation dynamics in the (pulse duration, wavelength, energy) parameter space. 2. Experimental results and model predictions on plasma energy density. 3. Modeling of plasma-induced hydrodynamic effects (breakdown - bubble formation and shock wave emission - bubble dynamics). 4. Partitioning of absorbed energy into a part necessary for the phase transition and parts going into bubble formation and shock wave emission. Partitioning is investigated as a function of volumetric plasma energy density, maximum bubble size (from macro to nano), and pulse duration (when is breakdown most “disruptive?). The comprehensive view on nonlinear energy deposition provides a framework for optimum laser parameter selection for different material processing tasks. Selection criteria are smooth onset and continuous tunability vs ‘big bang’, reproducability of energy deposition, and the disruptiveness of breakdown as a function of pulse duration.

Authors : N.Kutsevol, A.Naumenko, V.Chekhun
Affiliations : N.Kutsevol, A.Naumenko - Taras Shevchenko National University of Kyiv, Kyiv, Ukraine V.Chekhun - R.E. Kavetsky Institute of Experimental Pathology, Oncology and Radiobiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine

Resume : Photodynamic therapy (PDT) is a modern promising method of cancer therapy. It is characterized by lower systemic toxicity and fewer side effects as compared with radiation therapy and chemotherapy. The method works when three factors?light, a light-responsive substance (photosensitizer), and molecularoxygen?interact. Each of these individual components is harmless. However, upon irradiation with light of an appropriate wavelength, the photosensitizer becomes excited and transfers its energy to the surrounding molecular oxygen to generate cytotoxic singlet oxygen. The singlet oxygen can oxidize cellular macromolecules, inducing cell permeability alterations with the consequence of tumor cell death through apoptosis or necrosis. We have created a triple composite nanosystem consisting of gold nanoparticles in copolymer dextran-graft-polyacrylamide matrix and chlorin e6. These hybrid nanosystems have been studied by methods of optic spectroscopy and dynamic light scattering and tested in vitro on malignant cell line MT-4. Significant antitumor photodynamic activity of the nanocomposite photosensitizer was confirmed in experiments on photodynamic therapy of Lewis lung carcinoma, transplanted into laboratory mice, that warrants the photosensitizer prospective preclinical studies.

Authors : Zaneta Swiatkowska-Warkocka1, Tatiana Itina2, Alexander Pyatenko3, Naoto Koshizaki4, Marta Wolny-Marszalek1
Affiliations : 1. Institute of Nuclear Physics, Krakow, 31-342, Poland; 2. Laboratoire Hubert Curien, 42000 Saint-Etienne. France; 3. National Institute of Advanced Industrial Science and Technology, Tsukuba, 305-8565, Japan; 4. Hokkaido University, Sapporo, 060-8628, Japan.

Resume : In the last decades, laser processing has become an important route for producing nanoparticles. Pulsed laser ablation method uses a focusing laser beam which can bring high energy density on small areas on target what leads to explosive particles formation. Using an unfocused laser beam for irradiation nanoparticles dispersed in liquid results in a completely different formation of particles. These irradiated particles were melt, merged resulting in a submicrometer spherical particles formation. In this work taking metal oxides (alfa-Fe2O3, Fe3O4, CoO, NiO) particles as examples, we investigate and discuss the physical and chemical processes involved in particles formation by laser irradiation of nanoparticles dispersed in liquids. We will show the role of the solvent, and interaction not only between particles but also between particles and solvent molecules. The detailed discussion will be reported at the conference. We believe, that exploring the interactions between irradiated material and solvent molecules, and investigating the thermodynamic behavior of particles in various circumstances are needed to produce materials with specific structures and unique physical properties.

Authors : P. Camarda, L. Vaccaro, A. Sciortino, F. Messina, G. Buscarino, S. Agnello, F.M. Gelardi, M. Cannas
Affiliations : University of Palermo, Department of Physics and Chemistry, via Archirafi 36, I-90123, Palermo, Italy

Resume : One of the most intriguing challenges of modern nanotechnologies is the development of materials with physical/chemical properties favorable for highly efficient and color tunable lighting. To this purpose, pulsed laser ablation (PLA) is a versatile and environmentally friendly top-down strategy that is normally adopted to realize a large variety of luminescent nanomaterials. A key laser parameter is the pulse length (τ-laser) compared with the electron-phonon thermalization time, τ-therm, occurring in ps scale. In this work, we used two pulsed laser sources to irradiate a Zn target immersed in water, by which ZnO wurtzite nanocrystals (NCs) result from the Zn oxidation in water [1]: 1) Nd:YAG (1064 nm) emitting short pulses τ-laser≈ 5 ns >> τ-therm (thermal ablation); 2) Ti:Sapphire (800 nm) emitting ultra-short pulses τ-laser≈ 50 fs < τ-therm (non-thermal ablation). The different laser ablation settings strongly influence both the sizes and the optical properties of ZnO-NCs. Thermal ablation produces nanoparticles with sizes of ~30 nm that, under excitation above the direct bandgap (Eg ≈ 3.4 eV), emit two photoluminescence (PL) bands: the first, peaked at 3.3 eV (UV-band), is due to the excitonic recombination; the second, centered at 2.3 eV (green-band), is associated with oxygen vacancies [2]. In contrast, non-thermal ablation induces smaller nanoparticles with sizes <10 nm, that are comparable to the excitonic Bohr radius in ZnO-NCs, thus leading to quantum confinement effects. Indeed, both the optical gap and the UV and green PL bands shift towards higher energies on decreasing the ZnO-NCs sizes. Moreover, a third PL centered at 2.8 eV (blue-band), peculiar to fs PLA, is observed, its origin is still unclear. These results demonstrate that PLA is a successful method to synthesize ZnO nanosystems with controlled luminescence properties, thus increasing their application in lighting technologies. [1] P. Camarda, L. Vaccaro, F. Messina and M. Cannas, Appl. Phys. Lett. 107, (2015), 013103. [2] P. Camarda, F. Messina, L. Vaccaro, S. Agnello, G. Buscarino, R. Schneider, R. Popescu, D. Gerthsen, R. Lorenzi, F. M. Gelardi and M. Cannas, Phys. Chem. Chem. Phys. 18, (2016), 16237.

12:00 Lunch    
Diagnostics : Mihaela Filipescu
Authors : Changhao Liang, Dongshi Zhang, Chao Zhang, Jun Liu
Affiliations : Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China

Resume : Laser ablation of metal in organic solvents (LAMOS) has been proven to be an efficient technique for one-step synthesis of carbon-encapsulated metal/metal carbide/metal oxide core−shell nanostructures. However, the correlation between the influential factors and the final products, such as composition of the core and structure of the carbon shell, is still unclear to date. In this talk, comparative experiments of 16 transition metals were performed to clarify the panorama of LAMOS, including metal atomization and liquid decomposition into carbon and reductive gases, subsequent metal carbonization, surface precipitation, and metal-catalyzed graphitization to form amorphous and graphitic carbon shells. Importantly, it is found that the carbon solubility in metals and the affinity of metals to oxygen are the critical factors in determining the core composition: (1) inert metals Cu, Ag, Au, Pt, Pd are directly transformed into pure metal cores; (2) active metals Ti, V, Nb, Cr, Mo, W, Ni, Zr evolve into metal carbide cores, but Mn, Fe, and Zn give birth to the mixture of metal and metal oxides cores. Such processing obtained core-shell structure presented excellent performances in electrochemical applications due to their outstanding catalytic activity and stability.

Authors : Mónica Fernández1, Jesús del Val1, Mohamed Boutinguiza1, Antonio Riveiro1, Rafael Comesaña2, Fernando Lusquiños1, Cristian Covarrubias3, Fabiola Bastias3, Leyla Gómez4, Juan Pou1
Affiliations : 1.Applied Physics Department, University of Vigo, Spain. 2.Materials Eng., Applied Mech., and Construction Dpt., University of Vigo, Spain. 3.Laboratory of Nanobiomaterials, Institute for Research in Dental Sciences, Faculty of Dentistry, University of Chile, Independencia, Santiago, Chile 4.Laboratory of Microbiology, Department of Patology, Faculty of Dentistry, University of Chile, Independencia, Santiago, Chile

Resume : Metallic nanoparticles are receiving great attention as an alternative to overcome the continuous emergence of antibiotic-resistant bacteria. In this work Cu nanoparticles are prepared in liquid media by laser ablation to investigate their antibacterial activity. Colloidal solutions of Cu were prepared by ablating a copper metal foil submerged in distilled de-ionized water and methyl alcohol using a nanosecond Nd:YVO4 laser operating at 532 nm and a picosecond Nd:YVO4 operating at 1064 nm. Synthesized nanoparticles were characterized by X-ray diffraction (XRD), UV–Vis spectrophotometry, Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM). The antibacterial activity of the obtained nanoparticles by both laser sources and solvents was tested against Aggregatibacter actinomycetemcomitans, a gram negative bacteria which closely related to the dental implant failure. The kinetics of copper ion release was also tracked during the first 21 days by means of Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The obtained colloidal solutions resulted mainly in crystalline Cu nanoparticles ranging from few to 35 nm and rounded in shape. The nanoparticle size is more homogeneous when nanosecond laser is used as laser source and it decreases if methyl alcohol is used as solvent. Synthesized Cu nanoparticles exhibited inhibitory effect on bacteria strains with best results for those obtained by picosecond laser in water, which corresponds with a higher copper ion release. These results demonstrate not only the relation between copper nanoparticles size and their antibacterial activity, but also the influence of ion release on the biocidal process.

Authors : Valerio Pinchetti,1 Chiara Capitani,1,2 Graziella Gariano,2 Carlo Santambrogio,3 Mirko Prato,4 Rosaria Brescia,4 Andrea Camellini,5 Abhinav Anand,1 Margherita Zavelani-Rossi,5 Francesco Meinardi,1 Scott A. Crooker,6 & Sergio Brovelli1
Affiliations : 1 Dipartimento di Scienza dei Materiali, Università degli Studi di Milano – Bicocca, Via R. Cozzi 55, I-20125, Milano, Italy; 2 Glass to Power SpA, Via F. Daverio 6, I-20135, Milano, Italy; 3 Dipartimento di Scienze dell'Ambiente e del Territorio e di Scienze della Terra, Università degli Studi Milano-Bicocca, Piazza della Scienza, I-20125 Milano, Italy; 4 Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy; 5 Dipartimento di Energia, Politecnico di Milano and IFN-CNR, Milano, Italy. 6 National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, United States.

Resume : Electronic impurity doping of semiconductor nanocrystals (NCs) is a challenge in colloidal chemistry and holds promise in many photonic and spin-based nanotechnologies1. To date, our knowledge is limited to a few studies on a small number of compounds and dopants, with relevant electronic dopants still unexplored in nanoscale systems. Fine tuning of electronically doped NCs is also hampered by the statistical inhomogeneities of traditional approaches, restricting fundamental studies to statistical behaviours and complicating the realization of advanced devices. In our work2, we realize the first example of II-VI NCs electronically doped with an exact number of heterovalent gold atoms, a p-type impurity in bulk chalcogenides. Single-dopant accuracy across entire NC ensembles is obtained through a new non-injection synthesis employing Au clusters as ‘quantized’ dopant sources to seed the nucleation of CdSe NCs. Structural, spectroscopic and magneto-optical experiments trace a comprehensive picture of the physical processes due to the exact doping level of the NCs. Gold atoms are incorporated in CdSe NCs as nonmagnetic Au ions activating intragap photoluminescence. Fundamentally, the transient photoconversion of Au to Au2 artificially offsets the hole occupancy of the valence band states and results in diluted magnetic semiconductor behaviour revealing the contribution of individual paramagnetic centers to the magnetism of the NCs. 1Nat. Nano., 13 (2), 2018 2Nano Lett., In Press

Authors : S.A. Irimiciuc1, S. Gurlui2, P. Nica3, B. Hodoroaba4, M. Agop3, C. Focsa5
Affiliations : 1National Institute for Laser, Plasma and Radiation Physics – NILPRP, 409 Atomistilor Street, Bucharest, Romania 2Faculty of Physics, Atmosphere Optics, Spectroscopy and Lasers Laboratory “Alexandru Ioan Cuza” University of Iasi, 700506 Iasi, Romania 3Department of Physics, “Gh. Asachi” Technical University, 700050 Iasi, Romania 4University of Bucharest, Faculty of Physics, Bucharest – Magurele, Romania 5Univ. Lille, CNRS, UMR 8523 - PhLAM - Physique des Lasers, Atomes et Molécules, F-59000 Lille, France

Resume : Space-and time-resolved investigation techniques were implemented for the study of transient plasmas generated by laser ablation in various temporal regimes on a wide series of metallic and chalcogenide glass targets. The aim of this work was to implement two or three complementary investigation techniques in order to understand different aspects of the laser-produced plasmas. The experiments were performed on plasmas generated by ns, fs and ps laser ablation in similar irradiation (laser fluence: 5 - 20 J/cm2) and expansion conditions (p = 10-5 - 10-6 Torr). The optical investigations were performed by ICCD fast camera imaging and space- and time-resolved optical emission spectroscopy (OES), while for the analysis of the charged particles, the Langmuir probe (LP) method was implemented at various distances on the main expansion axis of the plasma plume. Despite the particularities of the laser-produced plasmas, the simultaneous use of both optical and electrical techniques was successfully implemented leading to quantitative comparisons between important plasma parameters extracted from each investigation technique. The global studies (ICCD imaging) revealed the splitting of laser plasma into two or three structures expanding with different center-of-mass velocities. The local investigations (OES and LP) allowed the determination of some key plasma parameters (temperatures, densities, collision rate or Debye length) related to the excited states from the plasma volume and the energy of the charged particles. The results are presented in a comparative manner discussing the effect of the pulse duration, laser fluence and target nature on the properties of the transient plasmas .

Authors : P.N. Terekhin (1, 2), P.D. Ndione (1), S.T. Weber (1), B. Rethfeld (1)
Affiliations : 1 - Department of Physics and OPTIMAS Research Center, Technische Universität Kaiserslautern, Erwin-Schroedinger-Strasse 46, 67663 Kaiserslautern, Germany 2 - National Research Centre ”Kurchatov Institute”, Kurchatov Sq. 1, 123182 Moscow, Russia

Resume : Surface nanostructuring is of great importance in technological applications. On a rough material surface ultrashort laser pulses can excite surface plasmon polaritons, i.e. surface plasmons coupled to a laser-electromagnetic wave. The interference of the plasmons wave and the incoming pulse leads to a periodic modulation of the deposited laser energy along the surface of a sample. The spatial and temporal evolution of the periodically modulated absorbed laser energy is studied after irradiation of gold in the framework of the two-temperature model (TTM). We present a new source term in the TTM, which takes into account the excited plasmon subsystem and therefore spatial periodicity. Our results show, that the electronic temperature follows the spatial profile of the source term. We investigate how these oscillations persist on large timescales when thermalization between electron and lattice subsystems is achieved, and we study their influence on the formation of surface structures. The developed method can be used to study the mechanisms of laser energy absorption under controlled conditions and the formation of the morphological effects. For example periodic surface structures, which could be of interest for medical applications, tribology, wetting, and others.

15:30 Coffee break    
Authors : Stefan Trautner (1), Chantal Zeppenfeld (1), Gerald Schwödiauer (1), Wolfgang Spendelhofer (2), Johannes Lackner (2), Johannes D. Pedarnig (1)
Affiliations : (1) Institute of Applied Physics, Johannes Kepler University, 4040 Linz, Austria; (2) KRAIBURG Austria GmbH & Co. KG, 5132 Geretsberg, Austria

Resume : Laser ablation and optical plasma spectroscopy of soft non-vulcanized rubber is reported. Bulk samples from industrial tire rubber production and thin film samples prepared from rubber solutions were ablated in ambient air by single-pulses (SP) and double-pulses (DP) of a Nd:YAG laser. The size of ablation craters was measured as function of number of laser pulses N and pulse energy E. The optical emission of laser-induced plasma was measured and the concentration of Sulphur and Zinc oxide was quantified (Laser-induced breakdown spectroscopy, LIBS). On bulk rubber the depth of ablation craters was strongly different for SP and DP irradiation. The crater diameters were almost constant. Emission lines of S and Zn were detected in the near IR and UV ranges, respectively [1]. Low limits of detection for S and ZnO were obtained [2]. On rubber thin films, the LIBS spectra showed an unexpected and strong decrease of emission intensity with increasing film thickness. Rubber films of same thickness revealed linear LIBS calibration curves. [1] S. Trautner et al., Laser-induced optical breakdown spectroscopy of polymer materials based on evaluation of molecular emission bands. Spectrochim. Acta Part A 174 (2017) 331-338. [2] S. Trautner et al., Quantification of the vulcanizing system of rubber in industrial tire rubber production by laser-induced breakdown spectroscopy (LIBS) (submitted to Anal. Chem.). Financial support by the Austrian Research Promotion Agency FFG (project 843546 imPACts, project 871974 PSSP) is acknowledged.

Authors : Kyriaki Savva, Bojana Višić, Ronit Popovitz-Biro, Athanasia Kostopoulou, Christina Lanara, Emmanuel Stratakis and Reshef Tenne
Affiliations : Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, 71110 Heraklion, Physics Department, University of Crete, Heraklion, 71004 Crete, Greece Weizmann Institute of Science, 7610001 Rehovot, Israel

Resume : The study of inorganic nanometer-scale materials with hollow closed-cage structures, such as inorganic fullerene-like nanostructures (IF) and nanotubes (INT), is a rapidly growing field. To date, numerous kinds of IF and INTs TMDs were synthesized for various applications, particularly for lubrication. In this work we demonstrate new simple, room temperature and environmentally friendly approaches for the synthesis of IF and INTs via a) ultrashort pulse laser ablation of TMDs in bulk form in ambient air as well as b) via pulsed laser deposition (PLD) of bulk TMD targets. In the first part is presented the synthesis of IF and INTs via ultrashort pulse laser ablation of a mixture of transition-metal dichalcogenides in bulk form mixed with Pb/PbO, in ambient air. The method can be considered as a synergy of photothermally and photochemically induced chemical transformations. In the second section is presented the application of the pulsed laser deposition technique (PLD) for the growth of hierarchical TMD structures, specifically the formation of WS2 nanostructures onto microstructures. These techniques can be further developed for the formation of nanostructures at any preselected location, such as microsized asperities, which are destined to numerous applications, including for electron emission cathodes and scanning probe microscopy field emitters.

Authors : Sergej Orlov, Pavel Gotovski, Paulius Šlevas, Justas Baltrukonis, Vytautas Jukna, Orestas Ulčinas, Titas Gertus
Affiliations : Center for Physical Sciences and Technology, Industrial laboratory for photonic technologies, Sauletekio ave 3, LT-10257 Vilnius, Lithuania

Resume : Geometrical phase elements (GPE) and their applications are booming nowadays: from devices like high NA metalenses to special optics like top-hat elements, from wavelengths in the ultraviolet to the THz diapason. The reason behind such flexibility is due to variety of different production approaches – lithography based, sculptured coatings etc. and due to the varying orientation and individual properties of sub-elements of the GPE. Such elements can act as both scalar and vectorial diffractive optical elements (or as shapers of the spatial spectra of the input beam), but usually their vectorial properties are largely ignored due to the complexity of mastering phases and amplitudes of both transverse components. Here, we propose a new polarization independent approach, which enables us to encode information into the both x and y components of the geometrical phase element. We report on our numerical study on the efficiency and feasibility of such elements. Moreover, we use a femtosecond laser based setup to inscribe nanogratings in the bulk of the glass. By controlling the orientation and retardance of those nanogratings we effectively manufacture a GPE, where the amplitudes of the x and y components are encoded independently. Lastly, we present an experimental study on few selected GPE’s, which were fabricated using new encoding technique.

19:00 Graduate Student Award ceremony followed by the social event    
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Laser writing of materials and applications : Alexandra Palla-Papavlu
Authors : P.M. Ossi
Affiliations : Dipartimento Energia, Politecnico di Milano, via Ponzio 34-3, 20133 Milano Mi, Italy

Resume : Therapeutic Drug Monitoring (TDM) is a clinical practice to assess the drug concentration in a biological fluid, usually blood plasma. TDM is critically important for Narrow Therapeutic Index (NTI) drugs, including Anti-Epileptic Drugs (AEDs), where small differences separate therapeutic from toxic doses. Blood concentration of AEDs is measured with the time consuming and costly Immunoassay tests, or High-Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS). Light scattering with ad hoc engineered plasmonic substrates made of noble metal (Au) nanoparticles (NPs) grown by pulsed laser ablation is a fast and comparatively inexpensive TDM approach for AEDs. Ablating in a transparent liquid a colloidal solution of Au NPs is obtained, while in a dense, inert, massive gas (Ar) NPs form in the expanding plasma plume and are deposited on an inert support (100-Si). Ambient gas pressure and laser pulse number in gas-phase synthesis and pulse duration and laser energy density in liquid-phase ablation affect the size, size distribution, shape and optical properties of the NPs and the NP arrays that self-assemble on the support, making possible to adjust the wavelength of the Surface Plasmon Resonance (SPR) peak. Thus, Surface Enhanced Raman Scattering (SERS) on samples of different origin, with various AEDs at concentrations of clinical interest become feasible. Our results on the SERS response of the AEDs Lamotrigine and Perampanel of relevant clinical interest are discussed.

Authors : V. H. Nguyen, C. Masse de la Huerta, S. Quessada, L. A. Angurel, L. C. Estepa, G. F. de la Fuente, D. Muñoz-Rojas
Affiliations : Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP, F-38000 Grenoble, France. ICMA(CSIC-Univ. Zaragoza), 50018, Zaragoza, Spain

Resume : The use of lasers to achieve transformations at interfaces, either on solids under air, controlled atmospheres or a diversity of liquid environments, is evolving at a fast pace and in-line with recent advances in photonic technologies. The singular properties of lasers, which provide a choice of emission parameters, such as emission wavelength, pulsed or cw mode and pulse width, together with the use of optomechanical means to scan in beam or line fashion, are ideal in order to trigger physico-chemical phenomena which are not available with alternative methods and are, at large, based on thermally activated processes. In this communication we will introduce the Laser Ablation Backwriting (LAB) method and we will show how it can be used to perform dry chemical reactions with spatial control and at room temperature. This research is supported by the project SPRINT (EU H2020-FETOPEN 801464).

Authors : Stéphane Guizard (1), Allan Bildé (2), Ahmed Maghraoui (1), Alexandros Mouskeftaras (3), Willem Boutu (1), Hamed Merdji (1).
Affiliations : 1: Laboratoire Interactions Dynamique Lasers, CEA Saclay, 91191 Gif Sur Yvette France; 2: Laboratoire des Solides Irradiés, CEA/CNRS/Ecole Polytechnique, 91118 Palaiseau,France; 3: Aix-Marseille University, CNRS, LP3, Marseille 13009, France.

Resume : When an intense ultrashort light pulse – in the visible domain- interacts with a wide band gap dielectric, a plasma can be generated by non-linear photoexcitation of carrier from the valence band to the initially empty conduction band. These carriers can be further excited in the conduction band, leading to an increase of their energy distribution, and thus of the amount of energy transferred to the material. If this deposited energy exceeds some critical threshold, permanent modification like damage or ablation may take place. The two key parameters determining the energy deposition are the density and the temperature of the plasma. In this presentation, we wish to demonstrate that a sequence of double pulse can be used to better control these two parameters, and thus to optimize energy deposition and facilitate for instance ablation of insulators and semi-conductors in the VUV domain. First, in the visible domain, using the second harmonic and the fundamental of a Ti-Sa laser, we show that time resolved double pump- and probe experiment allows to directly observe the sequence of events carrier excitation/ carrier heating, provided the parameters (energy, duration, delay) are appropriately chosen. Then, the ablation threshold (due to the first pulse) is dramatically reduced by the presence of the second pulse, while the characteristic of ablation are still determined by the first pulse [1]. Finally, new information regarding the excitation mechanisms, in particular impact ionization and avalanche are obtained [2]. In the second part, we show that this double pulse technique can be extended in the VUV domain. Using high order harmonics of a Ti-Sa laser (harmonic 25, ie. wavelength of 32 nm), whose intensity of far too low to damage any material, we could observe direct ablation of a dielectric, namely quartz, -SiO2, when the VUV pulse if followed by an IR pulse, whereas no effect is observed with each of these pulses alone. [1] Guizard, S.; Klimentov S.; Mouskeftaras A. ; Fedorov N., Geoffroy G.; Vilmart G., Applied Surface Science 336, p. 206, 2015. [2] A Mouskeftaras, S Guizard, N Fedorov, S Klimentov Applied Physics A 110 (3), 709-715, 2013.

Affiliations : 1 Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS-Université Bourgogne Franche-Comté (UBFC), 9 Av. A. Savary, BP 47 870, F-21078 Dijon Cedex; 2 Laboratoire PIMM, UMR 8006 CNRS/Arts & Métiers ParisTech, 151 Bd Hôpital, F-75013 PARIS; 3 NIMBE, CEA, CNRS, Université Paris-Saclay, CEA-Saclay, F-91191 Gif sur Yvette; 4 LEM3-UMR-CNRS 7239, 7 rue Félix Savart, BP 15082, F-57013 Metz Cedex 03

Resume : Advanced gas-turbine engines need new materials with excellent mechanical properties and resistance to high temperature oxidation. The combination of light-weight and good mechanical properties makes the titanium alloys very attractive for compressor section components [1]. Titanium offers the potential for component weight savings in the order of up to 50% compared to super alloys of Ni and steels. However, the mechanical properties of titanium deteriorate beyond 500 °C. Mechanical surface treatments such as shot-peening (SP) have shown their ability to improve the high temperature oxidation resistance of pure zirconium and titanium [2], but SP may be accompanied by surface pollution. Laser shock peening (LSP) appears as a good alternative to avoid this problem as it has been reported for pure titanium [3]. Here, we have investigated the effect of LSP treatments on the high temperature oxidation behavior of Ti-beta21S (TIMET, Ti-15Mo-3Nb-3Al-.2Si). LSP treated samples have been compared to untreated ones for oxidation times going from 5 to 3000 h at 700 °C in dry air. The mass gain variation was recorded by TGA for short durations. For long durations, the samples placed in a furnace set at 700 °C were periodically extracted to be weighed. Oxidized samples were studied by scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), x-ray photo-electron spectroscopy, nuclear reaction analysis, x-ray diffraction, micro-Raman spectroscopy and hardness measurements. A higher resistance of LSP treated samples against oxidation at 700 °C has been observed. The contribution of different mechanisms such as the changes in the microstructure due to the LS treatment and the eventual diffusion of nitrogen will be discussed.

09:45 Coffee break    
Authors : Paloma Fernández
Affiliations : Dept. Physics of Materials, Faculty of Physics, University Complutense

Resume : Metal oxide semiconductors are gaining more and more importance due to the many applications in fields as different as optoelectronics and photocatalysis, among many other. One of the most extensively studied materials in the group of MOS is ZnO. Nevertheless, many aspects of its use for the production functional nanostructures are still open. Probably the most challenging issues regarding this material, is to attain an efficient doping (in particular p-type). The tailoring of the material properties through the introduction of dopants is one of the most active fields in the ZnO research. However, the rise of severe environmental problems has brought to front different applications for which not only composition and defect structure is important. Photocatalys or sensing applications require surface conditions that can be achieved by laser treatment. Different patterning approaches in MOS substrates will be reviewed. As an example, polycrystalline substrates were structured by ultrafast laser pulses to induce the formation of Laser Induced Periodic Surface Structures (LIPSS). The performance of the irradiated areas as growth patterns for the production of highly ordered nanostructures was then analysed. Three main types of periodic structures were induced upon fs-laser structuring depending on the irradiation conditions: LSF (Low Spatial Frequency) and HSF (High Spatial Frequency) LIPSS and pseudo-spikes (PS). It has been found that the growth of micro- and nanostructures in the irradiated regions is much faster than in the non-irradiated ones. Our results indicate that using LIPSS as growth patterns can reduce the growth time to periods much shorter than those normally used from Vapor-Solid (VS) or Vapor- Liquid-Solid) VLS growth processes. Strong differences in morphology and luminescent properties are appreciated, not only between irradiated and non-irradiated areas, but also between areas irradiated under different conditions. The best regions to be used as growth templates for VS processes are found to be those irradiated in the highest energy deposition regime, featuring pseudospikes. This widens largely the current possibilities to tailor the characteristics of the grown structures

Authors : P. Sopeña (1,2), J.M. Fernández-Pradas (1,2), P. Serra (1,2)
Affiliations : (1) Department of Applied Physics, Universitat de Barcelona, Martí i Franquès 1, 08028, Barcelona, Spain (2) Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Av. Diagonal 645, 08028, Barcelona, Spain

Resume : Direct-write (DW) techniques stand out from other more conventional approaches for their ability to print inks in a digital manner, which is desirable for short production runs or in defect repair. Laser-induced forward transfer (LIFT) is a DW technique capable of transferring user-defined patterns by means of laser irradiation. In LIFT a layer of ink is spread on a transparent donor substrate and faced down, at a convenient gap, above a receiver substrate where the pattern will be printed. Then, a laser pulse is focused on the donor film and a portion of the ink is ejected towards the receiver, where it is deposited as a voxel. By printing multiple voxels in a sequential way any pattern can be reproduced. Unlike its major competitor, inkjet printing, LIFT allows depositing a wider range of ink rheologies, since it is nozzle-free and therefore not prone to clogging issues. This is especially relevant in printed electronics, where high solid content inks are usually required. In this study we investigate the LIFT of silver inks with high solid content for the fabrication of highly conductive pads. Through the variation of the main process parameters, such as laser pulse energy or donor-receiver gap, we determine the optimum working conditions that allow obtaining continuous conductive lines with the lowest sheet resistance. As a proof-of-concept of the feasibility of the technique, we print an RF inductor and show that it performs according to the design specifications.

11:15 Plenary Session 2    
12:30 Lunch    
Laser induced periodic structures : Esther Rebollar
Authors : P. Martinez, J. Gaudin, I. Papagiannouli, V. Blanchet, D. Descamps, C. Fourment, S. Petit, J. Y. Raty, N. Bernier, J.-B. Dory, P. Noé
Affiliations : CEntre Lasers Intenses et Applications, 43 rue Pierre Noailles, 33405 Talence, France ; CEntre Lasers Intenses et Applications, 43 rue Pierre Noailles, 33405 Talence, France ;CEntre Lasers Intenses et Applications, 43 rue Pierre Noailles, 33405 Talence, France ;CEntre Lasers Intenses et Applications, 43 rue Pierre Noailles, 33405 Talence, France ;CEntre Lasers Intenses et Applications, 43 rue Pierre Noailles, 33405 Talence, France ;CEntre Lasers Intenses et Applications, 43 rue Pierre Noailles, 33405 Talence, France ;CEntre Lasers Intenses et Applications, 43 rue Pierre Noailles, 33405 Talence, France ; Université de Liège, Institut de Physique B,5B-4000 Sart-Tilman, Belgium - Univ. Grenoble Alpes, CEA, LETI, MINATEC Campus, F-38054 Grenoble, France ; Univ. Grenoble Alpes, CEA, LETI, MINATEC Campus, F-38054 Grenoble, France ; Univ. Grenoble Alpes, CEA, LETI, MINATEC Campus, F-38054 Grenoble, France ; Univ. Grenoble Alpes, CEA, LETI, MINATEC Campus, F-38054 Grenoble, France

Resume : Chalcogenide Phase-Change Materials (PCMs), mainly GeSbTe-based alloys, have already been widely used for optical data storage (DVD-RAM or CD-RW). Thanks to their unique reversible and very fast amorphous to crystalline phase transition which is characterized by an uncommon huge change in optical and electrical properties. PCMs are now extensively studied to produce phase-change memory or aiming at developing further innovative non-volatile memories such as or storage class memories (SCM). The interaction of PCMs with a femtosecond light pulse has attracted significant attention since the possible non-thermal amorphous↔crystal phase transition could be used to drive the phase-change above the thermal “speed limits”. We used frequency domain interferometry (FDI), a pump-probe technique to investigate femtosecond dynamics in highly excited amorphous GeTe films. A pump pulse (25 fs, 800 nm, 1kHz) is used to trigger the phase transition. The interference patterns of the two probe pulses (120 fs, 532 nm) are measured simultaneously along S and P polarization to give access to complex refractive index as well as the surface hydrodynamics. In the sub-ps time scale a very rapid switch to a metallic state mainly attributed to the real part of the refractive index is observed while the surface is clearly moving within few hundreds of femtoseconds. Ab-initio simulations show that the change of chemical bonding of GeTe amorphous structure explains the trends observed in the experimental results.

Authors : Mario Garcia-Lechuga, Olivier Utéza, Nicolas Sanner, David Grojo
Affiliations : Aix Marseille Université, CNRS, LP3, UMR7341, 13288 Marseille, France

Resume : In the context of ultra-short pulse machining of transparent materials important progresses in terms of resolution, accuracy and quality of the induced modification have been realized. However, the experimental studies exploring the spectral domain have been rare, mainly due to the difficulties of obtaining sufficiently powered pulses at multiple wavelengths. In this work, we report on ablation thresholds of fused silica at 257 nm, 515 nm, 1030 nm, 1550 nm and 1900 nm; all obtained through non-linear optical processes by making use of the same femtosecond amplifier laser system (1030 nm wavelength and 180 fs pulse duration). Experiments have been carefully carried out ensuring similar irradiation conditions, making the comparison possible. Among the results, we observe the increase of the single-shot fluence ablation threshold from the ultraviolet to the near-infrared, followed by a saturation from 1030 to 1900 nm. Also, on the interest of exploring possible benefits on laser micromachining a morphological analysis of the craters is performed. We observed that once the energy threshold is exceeded, larger ablated depth and higher depth tuneability can be accessed with short-wave infrared pulses. As perspective, the values presented in this work can help for validation of theoretical models, as well as to suggest ablation strategies with longer wavelengths for extending the range of aspect ratio that can be accessed with femtosecond Gaussian beams.

Authors : M. Kanidi1,2, A. Dagkli3, N. Kelaidis4,5, D. Palles1, S. Aminalragia-Giamini4,6, J. Marquez-Velasco4,7, A. Colli8, A. Dimoulas4, E. Lidorikis3, M. Kandyla1, E.I. Kamitsos1
Affiliations : 1Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vasileos Constantinou Avenue, 11635 Athens, Greece; 2Department of Material Science, University of Patras, University Campus, 26504 Rio, Greece; 3Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina, Greece; 4Institute of Nanoscience and Nanotechnology, National Center for Scientific Research ‘Demokritos’, 15310 Athens, Greece; 5Faculty of Engineering, Environment and Computing, Coventry University, Priory Street, Coventry CV1 5FB, UK; 6Department of Physics, University of Athens, Zografou University Campus, 15784 Athens, Greece; 7Department of Physics, National Technical University of Athens, 9 Iroon Polytechniou st., 15780 Athens, Greece; 8Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, UK

Resume : We take advantage of the remarkable properties of graphene to combine it for the first time with 3D plasmonic nanostructured Si substrates for SERS. Large-area arrays of Si nanopillars were developed by femtosecond laser processing of Si in water. Coating the structured Si surface by a thin Au layer results in the spontaneous formation of Au nanoparticles. The whole process is scalable. Monolayer graphene was grown on a Cu foil by CVD and transferred on the substrates. Raman spectra were acquired with a Raman microscope (488, 514, 633, and 785 nm excitation). We also employed 3 reference substrates: a) nano-Si without Au, b) flat Si with 50-nm Au layer, c) pristine Si. We complement Raman measurements with FDTD simulations. The Raman signal of graphene on the plasmonic 3D substrate is enhanced by 2-3 orders of magnitude, which is comparable to the highest enhancements of graphene measured to date. For the first time, this enhancement is observed for all excitation wavelengths, across the entire visible spectrum. Numerical simulations elucidate the advantages of the substrate 3D topography. When the Si nanopillars are decorated with Au nanoparticles, graphene conforms around them as it bends between nanopillars, emitting a strong Raman signal. Due to synergistic effects with the Si nanopillars, the Au nanoparticles are no longer indistinguishable, as on a flat substrate. Instead, different nanoparticles become more active for different wavelengths and locations on the pillars. The Raman signal is calculated to increase monotonically with the depth of graphene bending, demonstrating the advantages of exploiting a 3D topography. These results pave the way for future real-world applications of large-area hybrid nanomaterials.

Authors : Catalin-Daniel Constantinescu [1], Emanuel Axente [2], Frédéric Pelascini [3], Jörg Hermann [4]
Affiliations : [1] University of Limoges / CNRS, SPCTS, 87068 Limoges, France; [2] National Institute for Lasers, Plasma and Radiation Physics, 77125 Măgurele, Ilfov, Romania; [3] Cetim Grand Est, 67305 Schiltigheim, France; [4] Aix-Marseille University / CNRS, LP3, 13009 Marseille, France

Resume : Elemental analyses of thin films with complex composition are challenging as the standard analytical techniques based on measurement calibration are difficult to apply. We show that calibration-free laser-induced breakdown spectroscopy (LIBS) presents a powerful solution, enabling quantitative analyses of multielemental thin films with analytical performances better than those obtained with other techniques. The demonstration is given for a nickel-chromium-molybdenum alloy film of 150 nm thickness that was produced by pulsed laser deposition. The LIBS spectra were recorded in experimental conditions that enable simple and accurate modeling of plasma emission [1]. Thus, a calibration-free approach based on the calculation of the spectral radiance of a uniform plasma in local thermodynamic equilibrium was applied to deduce the elemental composition. Supported by analyses via Rutherford backscattering spectrometry and energy-dispersive Xray spectroscopy, the LIBS measurements evidence nonstoichiometric mass transfer of the alloy during the thin film deposition process [2]. [1] Hermann J., Grojo D., Axente E., Gerhard C., Burger M., Craciun V., Phys. Rev. E 96, 053210 1-6 (2017) [2] Hermann J., Axente E., Pelascini F., Craciun V., Anal. Chem. //, online published (2019)

Authors : Igor Shishkovsky, Vladimir Scherbakov
Affiliations : Igor Shishkovsky - Skolkovo Institute of Science and Technology; Vladimir Scherbakov - Lebedev Physics Institute of RAS

Resume : In the present work, we demonstrated how powder bed fusion (PBF) technology can contribute to a better understanding of functional and structural properties of shape memory alloys (SMAs) in Ni-Ti systems. Correlation of specific resistance and phase structure in porous nickel-titanium intermetallic phases after the PBF was experimentally observed. The electrical resistivity of the phases studied (austenite, R-phase, martensite) was shown to increase with temperature but the slopes are quite different. The intermediate R-phase in nitinol (NiTi – intermetallic phase) shows generally higher electrical resistivity than the austenite phase, but its value grows with a decrease of temperature for the laser fused samples. We explained this fact by the accumulation of dislocation with the continuous increase of the R-phase with the temperature decrease. Hysteresis loop of the electrical resistivity is more remarkable in the laser sintered samples than in the laser melted ones due to different 3D part’s porosity and is a lot higher than that of solid material having a similar composition.

Authors : J. A. Hillier, D. C. Koutsogeorgis, S. Camelio, P. Patsalas, W. M. Cranton, A. Nabok, N. Kalfagiannis*
Affiliations : School of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, UK; School of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, UK; Institut Pprime, Université de Poitiers, TSA 41123, 86073 Poitiers cedex 9, France; Aristotle University of Thessaloniki, Department of Physics, GR-54124 Thessaloniki, Greece; Faculty of Science, Technology and Arts, Sheffield Hallam University, Howard St., Sheffield, S1 1WB, United Kingdom; Faculty of Science, Technology and Arts, Sheffield Hallam University, Howard St., Sheffield, S1 1WB, United Kingdom; School of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, UK

Resume : The ongoing development of nanofabrication capabilities ever increases our ability to exploit the light-matter interactions occurring at the nanoscale, promising breakthroughs in many technological sectors. To translate these capabilities into practical optical devices, we require materials which can expand the window of low-loss plasmonic responses into the IR. Transparent conductive oxides are appealing candidates due to their high DC conductivity, refractory character, durability and CMOS compatibility. An additional asset is their non-stoichiometric character which allows for modulating their opto-electronic properties. In this work we utilize excimer laser annealing on room temperature sputtered indium tin oxide, aluminium-doped zinc oxide and gallium-doped zinc oxide thin films in oxidising and reducing environments. We investigate the role of laser fluence, number of pulses and ambient composition in altering the crystal structure, composition and opto-electronic properties. We perform extensive characterization via Hall-effect, x-ray diffractometry, atomic force microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and spectroscopic ellipsometry in the wide spectral range from 0.3-40 μm. We report a modulation of the carrier mobility and concentration while preserving the amorphous nature of the thin films, providing a route to selectively tune the plasmonic response of TCO based nanostructures by controlling the laser annealing parameters.

15:30 Coffee break    
Authors : Michael GAUDIN (1), Pascal MARCHET (1), Laure HUITEMA (2), Aurelian CRUNTEANU (2), Frederic DUMAS-BOUCHIAT (1), Corinne CHAMPEAUX (1), Catalin CONSTANTINESCU (1)
Affiliations : (1) IRCER (UMR 7315) - CNRS / University of Limoges, F-87068 Limoges, France (2) Xlim (UMR 7252) - CNRS / University of Limoges, F-87060 Limoges, France

Resume : BST is a representative material whose dielectric constant can be controlled by applying a direct-current (DC) bias to change the capacitance in planar capacitors. We demonstrate a significant improvement in the growth of such perovskite dielectric films on (100), (110), and (111)-cut MgO substrates, with iridium (Ir) as bottom and top electrodes, in metal-insulator-metal planar micro-capacitors. 300-nm-thick Ba2/3Sr1/3TiO3 (BST) films are deposited by pulsed laser deposition (PLD) on top of 100 nm thick Ir films, to be used as bottom electrode. The Ir electrodes are also grown by PLD as a full film (bottom) and through a photo-lithographically designed masques, i.e. 125x125 µm, 250x250 µm, and 500x500 µm squares, serving as top electrodes, respectively. A numerical model of such MIM devices is considered in order to explain their electrical behaviour and properties. The design, fabrication and characterization of such tunable capacitive devices is presented and discussed with respect to their typically low losses even at high frequency, i.e. several kHz and up to several GHz, in low-to-medium power applications and providing high efficiency and tunability of up to 97-99%.

Authors : Noemí Casquero, Miguel Martinez-Calderon, Alejandro San-Blas, Angela Veiga, Mikel Gomez-Aranzadi, Santiago M. Olaizola, Ainara Rodriguez
Affiliations : a CEIT-IK4, Manuel Lardizabal 15, 20018 Donostia / San Sebastián, Spain b Universidad de Navarra, Tecnun, Manuel Lardizabal 13, 20018 Donostia / San Sebastián, Spain

Resume : In the last decades, numerous and intensive studies have been focused on the interaction between ultrashort laser pulses and solid surfaces to create micro- and nanostructures in metals to change their surface properties. In particular, Laser Induced Periodic Surface Structures (LIPSS) have been widely explored to produce surface corrugations for this purpose. Apart from the aforementioned topographical micro- and/or nano-modifications, most of the available studies report a laser induced modification of the material composition, together with an associated effect on the surface functionalities -either by increasing the wettability or by improving cell adhesion among others-. However, little efforts have been made in order to establish a correlation between the laser processing conditions and the resulting chemical modifications in the ultrashort pulse regime. In this work, we present an exhaustive EDX and XRD analysis of the oxide formation on Ti6Al4V surfaces as a function of laser irradiation parameters. Two different regimes were found: Low Spatial Frequency LIPSS with no oxide formation for low accumulated fluences and High Spatial Frequency LIPSS with an increasing oxygen content for higher accumulated fluences. The effect of the repetition rate of the laser source on the oxidation process is also studied and a discussion on the formation mechanism is presented.

Authors : S. Stephan, R. Streubel, C. McDonnell, H. P. Huber, S. Barcikowski, B. Gökce
Affiliations : University of Duisburg-Essen, Technical Chemistry I and Center of Nanointegration Duisburg-Essen (CENIDE), Universitaetsstrasse 7, Essen D-45141; University of Applied Sciences Munich, Department of Applied Sciences and Mechatronics, Lothstr. 34, 80335 Munich

Resume : Laser ablation in liquid is a versatile method for the production of nanoparticle colloids. However, due to the high purchasing price of laser systems this method is perceived to be expensive. In this contribution, we compare lasers of different price categories with regard to their maximal ablated mass per time (productivity), maximal ablated mass per time and power input (efficiency), and the resulting price per volume of colloid (economic efficiency). Moreover, the difference in laser ablation in air and in water is examined. Lasers with pulse durations of 3 ps, 1 ns and 5 ns are chosen and their fluence-dependent productivity is determined in a continuous flow experiment. From this data, the threshold fluence and the efficiency are extracted. For one, the ablation threshold fluence increases between 1.7 to 3.0 times, when changing from ablation in water to air. On the other side, the maximal productivity and the efficiency is higher in air. The latter can be correlated to beam shielding by the NP and redepositing of ablation material in the liquid environment. Comparing the ablation efficiency for the different laser systems in water, the 1 ns laser reached the highest value. Due to the low purchasing price of this system, a colloid can be produced the most efficient way with this system. We further find that compared with a commercially available colloid, the production of colloids via laser ablation in liquids is economically feasible for amounts larger than 4 mL per day.

Authors : Alina Irina CĂLUGĂR 1,2, Marius DUMITRU 1, Antoniu MOLDOVAN 1, Mihaela FILIPESCU 1, Maria DINESCU 1
Affiliations : 1 The National Institute for LaserS, Plasma & Radiation Physics (INFLPR), Atomistilor Street, No.409,Magurele city, Ilfov county, Postal code: RO-077125, Romania P.O. Box MG-36 2 University of Bucharest, Faculty of Physics, 405 Atomistilor, P.O. BOX MG-11, 077125, Magurele, Ilfov, Romania

Resume : High levels of atmospheric pollutants have a negative impact on human health and the environment. The sensitive sensors have great interest for an accurately measuring of pollutants. In this paper we present results regarding the active membrane of sensors based on metal oxide nanoparticles (NPs) (SnO2, WO3, CeO2 - materials with a wide band-gap semiconductor and remarkable chemical stability and electrical properties). These membranes were fabricated as thin films by MAPLE deposition technique on different type of substrates. In order, to obtain thin films with morphological, structural (AFM, SEM, XRD analyses) and electrical properties suitable for a qualitative response of the sensors, the deposition parameters (NPs concentration in the liquid, laser fluence, the solvent type) were varied. In particular, the CeO2-NPs (1% concentration in water) were uniformly distributed over the surface of the layer; the high roughness (RMS) around 107 nm indicates a large specific area required for sensors. In order, to achieve a uniform surface and high RMS, the concentration of WO3-NPs in the liquid and the laser fluence were varied. For SnO2, the sample obtained at lower laser fluence has a more uniform, denser surface than that obtained at higher fluence. „This work was supported by a grant of the Romanian Ministery of Research and Innovation, project number 33PCCDI/ 2018, within PNCDI III”.

Authors : S. Chertopalov, T. Zikmund, J.Bulíř, M. Novotný, E. Marešová, L. Volfová, J. Lančok
Affiliations : Institute of Physics of CAS, Na Slovance 2, Prague, 18221, Czech Republic

Resume : Fluoride doped by rare-earth (RE) makes them excellent for optoelectronics and photonics applications. However, due to the low absorption cross-section of the RE ions, the efficiency of the converting layer needs to be increased. One of concept to overcome this drawback is to combine RE with metallic nano-particles (NPs) which exhibit local surface plasmon resonance (LSPR) in UV and visible spectral range. The presentation reports on fabrication of metal-fluoride nanostructured thin films by pulsed laser deposition and evaporation supported by auxiliary plasma. This method operates under new physical conditions. Therefore, it makes possible to fabricate new advanced nanostructured films with unique functional properties such as the metal fluoride films with a unique plasmonic and luminescence properties. In our work we demonstrated successfully fabrication of Ag, Al and Bi NPs embedded by LiF , CaF2 and Pr3+:CaF2 films. The fabrication of metallic NPs in UHV conditions embedded in fluoride matrix prevent the oxidation, which could degrade of plasmonic properties of NPs. The effect of additional laser annealing on crystalline structure of the metals nanoparticles will be presented. The prepared layers were analysed by spectral ellipsometers in the spectral range from 145 nm to 5000 nm. The analysis of the measured date revealed an absorption band in the range from 200nm up to 450 nm corresponds to LSPR of incorporated metallic NPs depending on the metals and size, respectively. The calculated absorption cross absorption effective cross-section will be compared with experimental results.

Authors : N. Khemiri, D. Abdelkader, F. Antoni, M. Kanzari
Affiliations : Université Tunis El Manar, Ecole Nationale d’Ingénieurs de Tunis, Laboratoire de Photovoltaïque et Matériaux Semi-conducteurs, BP37, 1002 Le Belvédère, Tunis, Tunisie Université de Tunis El Manar, Institut Préparatoire aux Etudes d'Ingénieurs El Manar, BP 244, Tunis 2092, Tunisie ICube-Laboratoire des Sciences de l’Ingénieur, de l’Informatique et de l’Imagerie, Université de Strasbourg-CNRS, 23, rue du Loess, 67037 Strasbourg Cedex, France

Resume : Tin antimony sulfide (SnSb4S7) is one of the most promising compounds for the next generation of optoelectronic and thin film photovoltaic devices. SnSb4S7 material was synthesized by a solid-state reaction using earth-abundant tin, antimony and sulfur elements. The effects of excimer laser annealing (ELA) at different pulse energies on the structural, morphological and optical properties of thermally evaporated SnSb4S7 films were investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy measurements showed that the films annealed by an excimer laser of 248 nm were amorphous for weak energy densities whereas the sample irradiated with 111 mJ/cm-2 was polycrystalline with a preferential orientation. The ELA effects on the optical properties were also studied in the wavelength range 300-1800 nm by using UV-Vis-NIR spectroscopy. The absorption coefficient of all samples in the fundamental absorption region is higher than 104 cm-1. We also found that the optical band gap decreases from 2.04 to 1.84 eV after irradiating the thin films under different laser energy densities.

Authors : V.I. Mazhukin, M.M. Demin, A.V. Shapranov, A.V.Mazhukin
Affiliations : Keldysh Institute of Applied Mathematics of RAS, National Research Nuclear University MEPhI

Resume : The use of ultrashort superpower pulses in modern laser technologies is accompanied by the appearance of new physical phenomena. Their study leads to the need to make appropriate adjustments to the mathematical models used. One of these effects is the effect of pressure of collectivized electrons in a metal under conditions of strong thermodynamic nonequilibrium. The correct formulation of the mathematical model in the continual approximation is carried out within the framework of the single-speed two-temperature hydrodynamic model. In the atomistic model, by analogy with the continual model, an additional force arises in the equations of motion (the so-called blast force) from the electronic subsystem in the form of a gradient of the “non-equilibrium” part of the electronic pressure. The effect of electron pressure was studied in a series of computational experiments based on the molecular dynamics simulation of femtosecond action on an Al target. A large gradient of electron pressure at the surface at an early stage of development leads to the breakaway of a thin subsurface subnanometer layer of matter flying away at high speed. At the stage of a slower process of unloading ionic pressure, a rarefaction wave with negative pressure is formed, leading to the separation of melt films with a thickness of 10-20 nm. The speed of dispersion of liquid fragments is significantly lower than the speed of the first split layer. This work was supported by RSF, project 18-11-00318.

Authors : N. Tarasenka, V. Kiris, A. Nevar, N. Tarasenko
Affiliations : B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus

Resume : In this paper, we demonstrate the capabilities of liquid assisted laser ablation technique in combination with laser-induced modification for synthesis of binary SiSn and GeSn nanocrystals (NCs). Nanostructures based on the GexSn1-x and SixSn1-x alloys are interesting due to the possibility of adjusting the lattice parameters and the width of the band gap, changing the mobility of charge carriers that makes them promising for the applications in optoelectronics and photovoltaics. For the alloyed NCs synthesis a two-step technique was developed based on the laser ablation of a germanium (silicon) target immersed in a cell filled with the preliminarily prepared Sn suspension in ethanol with the subsequent laser irradiation of the formed colloid. For the ablation and additional irradiation the Nd3+: YAG laser (1064 nm, energy 80 mJ/pulse, repetition rate 10 Hz, pulse duration 10 ns) and its second harmonic (532 nm) were used, respectively. The phase composition, morphology, structure and optical properties of the synthesized NCs have been investigated. Laser induced rapid heating, subsequent co-melting, and re-solidification processes at high cooling rates have been considered to be experimentally achieved at the optimized laser processing parameters. The prepared NCs with an average diameter of about 5 nm exhibited a shift of the Raman peaks attributable to Ge and Si (to the lower wavenumbers) that can indicate the incorporation of Sn into the lattice and alloy formation. The potential of the prepared alloyed NCs as a photovoltaic material will be demonstrated.

Authors : A. Guarnaccio 1, C. Belviso 2, A. Santagata 1*, P. Dolce 1, E. Lucia 1, G. Grippo 1, D. Mollica 1, A. Bellucci 3, A. De Stefanis 3, F. Toschi 3, D. M. Trucchi 3, V. Valentini 3, F. Cavalcante 2, A. Lettino 2, L. Medici 2, P. P. Ragone 2, S. Orlando 1 (* corresponding author)
Affiliations : 1 CNR – ISM, Sede di Tito Scalo, Zona Industriale di Tito Scalo; 85050 (PZ), Italy; 2 CNR – IMAA, Zona Industriale di Tito Scalo; 85050 (PZ), Italy; 3 CNR – ISM, Sede di Montelibretti, Via Salaria Km 29,300; 00016 Montelibretti (RM), Italy.

Resume : Polymers are replacing progressively metals and metallic alloys in technological applications over the past few decades and there is great interest in physico-chemical treatments for modifying polymeric surfaces. The aim of our studies is to change physical and chemical properties of the polymeric surfaces in order to enhance performances in some specific applications such as automotive. Laser treatments are of particular interest in morphological and chemical modifications of the polymer for nano-particles coating and surface functionalization in general. We employed a fs Ti:Sa laser source in order to evidence differences in the obtained results induced by photo-chemical, photo-physical, and photo-thermal processes by means the change of the main laser parameters such as: pulse energy, spot dimension according to the distance of the focused laser beam to the sample surface. Laser-irradiated samples were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffraction (XRD), m-Raman spectroscopy, FT-IR spectroscopy and contact angle measurement. Morphological results indicated that ripple-like structures of micrometer and sub-micrometer size were formed after the laser irradiation keeping the main chemical features of polymer surface.

Authors : A.F. Bonciu 1,2; S. Iosub 3; M. Filipescu 1;V. Dinca and M. Dinescu 1
Affiliations : 1) National Institute for Lasers, Plasma and Radiation Physics, Magurele, Bucharest, 077125, Romania 2) University of Bucharest, Faculty of Physics, RO 077125, Magurele, Romania; 3) Institute of Biochemistry of the Romanian Academy, 060031 Bucharest, Romania;

Resume : In the last decades, there is an increased interest in developing strategies for improving bio-interfaces in the field of orthopedic implants. Understanding interaction of cells with bio-interfaces is essential to the design of scaffolds that can control cell adhesion, proliferation and differentiation in regenerative medicine. Ceria nanostructures may not only improve the biointerface mechanical properties, but also stimulate the regenerating tissue biochemical activity. It is well-known that formation of compounds derived from molecular oxygen (i.e. hydroxyl radicals, hydrogen peroxide) during cellular growth hinders cell proliferation, which can be prevented by nanostructured CeO2 that neutralize the oxidative stress. Based on the unique benefits of ceria on cells, the aim of this work was to prepare specific micro and nanostructured CeO2 films, and to determine their in vitro biological performance as correlated to the coating architecture. Pulsed Laser Deposition (PLD) method was used for obtaining CeO2 thin films. The resulting morphologies and the main features were characterized using scanning electron microscope (SEM). The wetting behavior and surface free energy of CeO2 films were studied using the contact angle measurement. The initial adhesion of the MG-63 osteosarcoma cell and the effect of the micro and nanostructured coatings on their morphology and adhesion was analyzed by fluorescence and SEM microscopy. It was observed that the different structured ceria films obtained by PLD influenced especially the early response of MG-63 cells, but with little influence on viability, therefore being promising candidates for improved orthopedic implants. In perspective, different cells lines response will be analyzed toward establishing an osteogenic response.

Authors : N. Nedyalkov1, M. Koleva1, N. Stankova1, R. Nikov1, A. Dikovska1, L. Aleksandrov2, R. Iordanova2, E. Iordanova3, G. Yankov3, K. Grochowska4, G. Sliwinski4
Affiliations : 1Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784, Bulgaria; 2Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. Georgi Bonchev str. bld.11, 1113 Sofia, Bulgaria; 3Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784, Bulgaria; 4Department of Photophysics, The Szewalski Institute, Polish Academy of Sciences, Fiszera 14, Gdańsk 80-231, Poland

Resume : The process of laser radiation induced formation and decomposition of Ag nanoparticles in glass is studied. Glass samples with composition of 50 wt% SiO2, 20 wt% Al2O3, 20 wt% B2O3, 5 wt% CaO, 2 wt% Li2O, 3 wt% MgO are fabricated by melt quenching method. AgNO3 is added in the fabrication stage in amount to form final glass samples with compositions of 0.1 and 1 wt% Ag. The fabricated samples are irradiated by laser pulses delivered by Nd:YAG nanosecond and Ti:sapphire femtosecond laser systems. The laser parameters as wavelength, fluence and the applied pulse number are varied in a broad range in order to estimate the glass response. It is found that at certain conditions laser radiation can induce direct formation of silver nanoparticles in the irradiated zones. The process is different from the already presented in the literature that requires annealing after the laser processing. Based on XPS, TEM, and optical transmission and luminescence analyses the mechanism of nanoparticles formation is discussed. It is also found that the laser radiation of the formed nanoparticles can result in their decomposition. The efficiency of the process is studied for a wide range of laser parameters for both nanosecond and femtosecond laser pulses. In this process a complete recovery of the native glass optical properties can be achieved. The obtained results can be used in a technology for modification of the optical properties of composite glasses and design of complex photonic and data storage devises.

Authors : H.H. Gullu 1, O. Bayrakli Surucu 2, M. Terlemezoglu 3,4,5, C. Emir 1, and M. Parlak 4,5
Affiliations : 1-Department of Electrical and Electronics Engineering, Atilim University, Ankara 06830, Turkey; 2-Department of Physics, Kirsehir Ahi Evran University, Kirsehir 40200, Turkey; 3-Department of Physics, Tekirdag Namık Kemal University, Tekirdag 59030, Turkey; 4-Department of Physics, Middle East Technical University, Ankara 06800, Turkey; 5-Center for Solar Energy Research and Applications (GÜNAM), Middle East Technical University, Ankara 06800, Turkey

Resume : II-VI semiconducting chalcogenides have become a great part of research interest due to their possibility to use in a wide range of device applications with their remarkable optoelectronic properties as ideal direct band gap, high absorption coefficient and photosensitive behavior in the visible region of spectrum. Based on these optical and electrical properties, these compounds have been investigated as an alternative material system in the fabrication of low cost optoelectronic devices and used as promising materials for the development of current technological devices. Among these compounds, cadmium selenide (CdSe) thin film has long been popular in the field of optoelectronics due to their high transparency in visible region, direct and wide band gap value, photoconductivity, high electron affinity and n-type semiconducting behavior. Although this type of films have potential applications in fabrication of light emitting diodes, thin film transistors, gas sensors, photodetectors and solar cells, in recent years, attention has been directed to alternative methods as variations in chemical constituents, doping, formation of ternary analogues, surface patterning in order to manipulate the material characteristics of thin films to improve the performance of the devices. In this study, CdSe thin films were deposited on a soda-lime bare glass and indium tin oxide (ITO) coated glass substrates using direct evaporation of high purity and stoichiometric CdSe powder at room temperature. Bare glass substrates were used in thin film characterization processes and ITO coated glass substrates was employed to create transparent conducting oxide layer for possible device applications. For the deposited CdSe thin films, energy dispersive X-ray (EDS) analysis showed an average atomic percentage of CdSe is near to stoichiometric composition of the source material as Cd:Se ratio (50:50). The X-ray diffraction profile of the samples was indexed according to JCPDS files and the characteristics diffraction peaks were observed in a good agreement with the literature without any formation of secondary phase in the structure. The surface imaging using scanning electron microscopy (SEM) and detailed surface morphology analysis by using atomic force microscope (AFM) showed that the deposited CdSe thin films are dense and compact in nature. From the optical transmission studies, films were found in direct optical transition characteristics and the band gap values of the samples were calculated using Tauc plots. In addition to the film analysis on different substrates, substrate-assisted laser patterning was investigated as an alternative technique to create functional structures for possible optoelectronic applications. The straight and continuous line patterns on bare and ITO coated glass substrates were optimized in terms of pulse repetition rate, laser power, pulse energy and the feeding speed of the nanosecond pulsed Nd:YAG laser system. Uniform periodic pattern without any damage to the glass substrates were achieved with a wavelength in the infrared region. It was observed from EDS spectrum of the films that the stoichiometric transfer of material from source powder to the deposited films on different substrates with different line patterns was achieved. In the case of surface morphology, the effects of laser patterning on characteristics of the CdSe thin films deposited on bare and coated glass substrates were investigated by SEM and AFM images. UV/Vis spectrophotometer was used to discuss the transmittance and reflectance characteristics of these patterned samples. Acknowledgement: This work was partially supported by the Scientific and Technological Research Council of Turkey (TUBITAK) Project No: 118F317

Affiliations : 1Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS-Université Bourgogne Franche-Comté (UBFC), 9 Av. A. Savary, BP 47 870, F-21078 Dijon Cedex 2 NIMBE, CEA, CNRS, Université Paris-Saclay, CEA-Saclay, F-91191 Gif sur Yvette 3 Laboratoire PIMM, UMR 8006 CNRS/Arts & Métiers ParisTech, 151 Bd Hôpital, F-75013 PARIS

Resume : The increase of aeronautical transport with environmental constraint needs to make planes as fuel-efficient as possible. One of the solutions is to make aircrafts lighter. Some materials, especially the dense nickel alloys, should be substituted with lighter materials. To improve some of the materials properties mechanical treatments could be efficient, like shot peening [1] or laser shock peening [2]. In this last case, laser irradiance must be very high, above 10 GW/cm², which needs powerful specially designed laser sources. Laser irradiance effects on the composition modification of the extreme surface of pure titanium was studied during the first stage of high temperature oxidation, at 700 °C. Laser shock-peening treatments with irradiance in the range of 2 to 11 GW/cm² were performed. Direct surface analysis of laser-shocked and oxidized samples were conducted by SEM/EDS microprobe and completed by Ion Beam Analysis (IBA) to observe the evolution of light elements like nitrogen and oxygen during the different steps of oxidation. A furnace coupled with XPS analysis allowed us to investigate the superficial layers of laser-shocked samples after short oxidations. Raman spectroscopy shows rutile formation. Analyses underline that the oxidation of pure titanium leads to nitrogen insertions under the native rutile oxide. For longer exposures, up to 100 h, the concentration of large quantities of nitrogen was revealed at the oxide/-case interface for the laser-shocked samples. This accumulation could be the main reason of the improved oxidation resistance of laser-shocked pure titanium in air at 700°C. References [1] A. Kanjer et al., Surf. Coat. Technol. 326 (2017), 146–155. [2] A. Kanjer et al., Surf. Coat. Technol. 343, (2018) 93-100.

Affiliations : 1Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS-Université Bourgogne Franche-Comté (UBFC), 9 Av. A. Savary, BP 47 870, F-21078 Dijon Cedex 2 LEM3-UMR-CNRS 7239, 7 rue Félix Savart, BP 15082, F-57013 Metz Cedex 03 3 Laboratoire PIMM, UMR 8006 CNRS/Arts & Métiers ParisTech, 151 Bd Hôpital, F-75013 PARIS

Resume : Titanium is a metallic material with good mechanical properties, very interesting in aeronautic applications for its low-weight characteristic. Unfortunately, the oxidation resistance of this material drastically decreases over 550°C. To improve the oxidation resistance some mechanical treatments as shot peening and laser-shock peening can be applied. Nevertheless, the origin of the improvement of this oxidation resistance is not yet clearly understood. Previous studies underlined the importance of some parameters of the treatments on the mechanical efficiency of LSP. In this study, we explore the influence of two parameters (the number of impact per area and the laser irradiance value) on the microstructural modifications. The number of superposed impacts varies from one to three. The laser irradiance was in the range of 8 and 9 GW/cm2. The higher value is suggested by previous studies. The impact zones were observed by 3D optical microscopy and interferometric analysis. Cross-section observations were made by SEM (in BSE mode) and EBSD. The microstructure evolution as a function of the number of impact and laser irradiance was highlighted. The type and density of twinning seem to be the most affected features. These evolutions give some explanations on the effect of the shock wave on the local modifications inside the material. Compressive twins are directly induced during direct shock wave, while tensile twins are produced by interference between the main and secondary reflected waves. Previous works showed that the LSP treatment led on the whole sample surface induces thinner oxide layers than on untreated samples. In this work samples with single impact zone of few mm of diameter were oxidized under air at 700°C. The oxide layer in the laser-impacted zones was similar with those of non-impacted areas. This suggests that, for protection against oxidation purposes, the laser-shock penning treatment needs a large surface recovery.

Authors : R. Saifutyarov*, A. Barkanov*, O. Petrova*, I. Taydakov**, A. Akkuzina*, A. Khomyakov*, A. Lipatiev*, V. Sigaev*, V. Korshunov***, R. Avetisov*, I. Avetissov*
Affiliations : *Dmitry Mendeleev University of Chemical Technology of Russia **P. N. Lebedev Physical Institute, Russian Academy of Science *** Bauman Moscow State Technical University

Resume : Nanoscale hybrid luminescent structures are promising for development of a new generation of long-live storage devices with high resolution and easy fast access. One of the techniques for organic-inorganic hybrid materials synthesis is a melt synthesis when the exchange reaction between organic constituent and metal ions of inorganic matrices results in the formation of hybrid material with new luminescent properties. In the research we conducted the exchange reaction by the action both femtosecond and continuous-wave lasers on nanosize heterogenic or multilayer films preliminary fabricated by thermal sputtering on a substrate. As initial materials high pure metal-organic complexes of 8-hydroxyquinoline with aluminum and gallium and inorganic binary compounds (PbO, PbF2, B2O3) were used. The obtained 2D HM images demonstrated strong difference in luminescent characteristics depending on the initial materials and preparation conditions. The research was financially supported by the grant of the Ministry of Science and High Education of the Russian Federation, project ID RFMEFI57418X0186.

Authors : T.T.D. Huynh1, M. Tabbal2, AL. Thomann1, H. Rabat1, E. Millon1, N. Semmar1
Affiliations : 1- GREMI-UMR 7344-CNRS-University of Orleans, 14 rue d’Issoudun, BP6744, 45071 Orleans Cedex2, France 2- Department of Physics, American University of Beirut, Bliss St., P.O. Box: 11-0236, Beirut, Lebanon 1107 2020.

Resume : Titanium oxide, Copper and titanium thin films (with closely 200 nm thickness) are grown on Si substrate using magnetron-sputtering technique. The first objective is to establish the incubation curves for ultrashort beams (fs and ps) at 266 nm. The working fluences are in the range 10 to 500 mJ/cm2 and the number of pulses is varied from 10 to 105. The induced micro-craters are analyzed by Scanning electron microscopy (SEM) and interferometric optical microscopy (IOM). The last technique allows to scan the micro/nano craters in order to evaluate the anisotropy of the ablation mechanisms in correlation to the laser ablation regime. Two kind of incubation curves (by SEM and IOM are compared and discussed and the corresponding incubation curves are proposed. The LIPSS formation conditions (regular LIPSS, spikes and dots) under both laser beams (fs and ps) are also investigated and discussed versus the incubation phenomena in each thin film case.

Authors : R. Milazzo,(1,5) C. Carraro,(1,5) G. Impellizzeri,(2) J. Frigerio,(3) A. Ballabio,(3) A. Pecora,(4) A. Sanson,(1) D. De Salvador,(1,5) D. Scarpa,(5) A. Andrighetto,(5) A. Portavoce,(6) D. Mangelinck,(6) M. Ortolani,(7) G. Isella,(3) G. Fortunato,(4) A. Carnera,(1) and E. Napolitani(1,2,5)
Affiliations : (1) Dipartimento di Fisica e Astronomia, Università di Padova, Via Marzolo 8, I-35131 Padova, Italy; (2) CNR-IMM, via S Sofia 64, I-95123; (3) L-NESS, Dipartimento di Fisica, Politecnico di Milano, Polo di Como, Via Anzani 42, I-22100 Como, Italy; (4) CNR-IMM, Via del Fosso del Cavaliere 100, 00133 Roma, Italy; (5) Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Viale dell’Università 2, 35020 Legnaro (PD), Italy; (6) IM2NP, CNRS-Universités d’Aix-Marseille et de Toulon, Faculté de saint Jérôme, 13397 Marseille, France; (7) Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Rome, Italy;

Resume : Owing to its high carrier mobility as well as compatibility with silicon-based technology, germanium recently attracted a renewed interest for its high performances in various technological area such as photonics, nano- and opto-electronics. Nevertheless, Ge-based devices often require both very high (>1e20 cm^-3) and ultra-shallow doping, which are challenging for most of dopants due to their low solubility and high diffusivity. For this purpose, pulsed laser melting (PLM) is the most promising technique, being able to promote ultra-fast liquid phase epitaxial regrowth allowing both enhancement of incorporation together with diffusion confinement, at the same time. Our latest experimental results on p- and n-type doping of Ge or Ge-on-Si as obtained by performing PLM in different conditions will be presented. In particular, the talk will be focused on possible issues (like contaminations, clustering and thermal stability) along with different strategies employed to improve electrical activation and to meet different applications: for example, PLM combined with ion-implantation or in-situ doping. Fundamental information about non-equilibrium diffusion or strain evolution will be discussed thanks to advanced chemical (1D and 3D), electrical and structural characterizations with nanometer resolution.

Authors : Sergey V. Starinskiy 1,2, Alexander V. Bulgakov 1,3, Elizaveta Gatapova 1,2, Yuri G. Shukhov 1, Veronica Sulyaeva 4, Nikolay Timoshenko 1, Alexey Safonov 1
Affiliations : 1 Kutateladze Institute of Thermophysics SB RAS; Novosibirsk, Russia 2 Novosibirsk State University, Russia 3 HiLASE Centre, Institute of Physics ASCR, Dolni Brezany, Czech Republic 4 Nikolaev Institute of Inorganic Chemistry SB RAS; Novosibirsk, Russia

Resume : The laser treatment is widely used to control the wettability properties of material surfaces. In present work we propose a novel approach for obtaining of silicon surfaces ensuring an arbitrary apparent contact angle within the range from 0° to 170° for water. We found a narrow range of regimes of infrared laser irradiation leading to formation of a unique self-organized structure on the silicon surface – microcolumn grid with spacing about tens microns. Formation of the structure within the laser spot is due to a combination of ablation, oxidation, product ablation redeposition and cracking along the crystal lattice. A study of degradation of the self-organized structure for overlapping laser spots was carried out. It is demonstrated that scanning of the laser beam in the regimes of self-organized structure formation on the silicon substrate allows to obtain an extended surface area with superhydrophilic properties. The extreme wettability retains preserved when the samples are stored in air for six months. Hot-wire CVD of fluoropolymer coating onto the superhydrophilc silicon was used to further control the silicon wettability properties. An increase in the fluoropolymer film thickness up to 100 nm allows to change gradually the surface from superhydrophilic to superhydrophobic. The wettability properties of the produced fluoropolymer–silicon system were analyzed using the Wenzel and Cassie theories. The work was supported by the Russian Science Foundation (grant number 18-79-10119).

Authors : O.N. Koroleva, A.V. Mazhukin, V.I. Mazhukin
Affiliations : Keldysh Institute of Applied Mathematics of RAS, National Research Nuclear University MEPhI

Resume : Laser treatment of silicon with short pulses has been rapidly developing over the past few decades. The ability to deposit large amounts of energy in a densely localized area has found use in pico- and femtosecond laser processing and nanostructuring of semiconductors. Nevertheless, the fundamental mechanisms underlying such processes as ultrafast melting, layering and removal of matter, caused by laser radiation are still the subject of scientific debate. A theoretical study of these mechanisms, based on mathematical modeling, is faced with the problem of determining material properties in a wide range of temperature and pressure. Polymorphic transformations in silicon, arising from the transition of a substance from one crystalline state to another, affect its properties. In the vicinity of the phase transition, all properties undergo qualitative changes and significantly differ from similar characteristics of metals. The report presents the properties of silicon in a wide range of temperature and pressure including the critical region, obtained using molecular dynamics modeling. Such important characteristics of Si as the pressure dependences of the temperature and heat of melting, temperature dependences of the heat of evaporation, the coefficient of linear expansion, heat capacity, and density are determined. Results are compared with experimental data. This work was supported by RSF, project 18-11-00318.

Authors : A. Nikolov (1), N. Stankova (1), N. Nedyalkov (1) and D. Karashanova (2)
Affiliations : (1) Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria (2) Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences, Acad. G. Bonchev str., bld. 109, 1113 Sofia, Bulgaria

Resume : The second harmonic (λSH = 532 nm) of a Nd:YAG system is utilized to produce nanowire networks by pulsed laser ablation of a silver target immersed in double-distilled water. A static electrical field is applied perpendicularly to the direction of the laser beam propagation to investigate its impact on the nanowires formation. The intensity of the electric field and the fluence of the laser beam are varied. The profile of the optical transmission spectrum is used to indirectly assess the morphology of the material being ablated. The nanostructures obtained are visualized by transmission electron microscopy and their microstructure is studied by selected area electron diffraction (SAED). The nanowire networks are of importance for biomedical application and in surface-enhanced Raman spectroscopy.

Authors : D. Craciun1, I. Anghel1, S. Irimiciuc1, B. Hodoroaba2, G. Dorcioman1, P. Garoi1, O. Uteza3, and V. Craciun1, 4
Affiliations : 1National Institute for Lasers, Plasma and Radiation Physics, Măgurele, Romania; 2Physics Faculty, University of Bucharest, Magurele, Romania; 3Laboratoire LP3, Universite de Marseille, Campus de Luminy, Marseille, France; 4Extreme Light Infrastructure-Nuclear Physics, Magurele, Romania

Resume : Recent advances in ultra-high power fs-laser physics and technology materialized in the construction of several operational PW-level installations worldwide. Beam steering and focalization at such high intensities is performed using high quality mirrors, which are using either dielectric layers/multilayers or metallic layers. We used the pulsed laser deposition technique (PLD) to obtain thin HfO2 and ZrO2 dielectric layers that were investigated as coatings for fs-lasers mirrors. The PLD installation uses an ArF excimer laser, since its 193 nm radiation is better absorbed in oxide targets than the 248 nmwavelength of KrF lasers. Films were deposited on Si and quartz substrates under various oxygen pressures to optimize their optical properties. The single and multiple pulses fs laser damage threshold (LDT) of deposited films were tested using two laser installations. One installation is a CPA 2101 (Clark - MXR) system who delivers pulses at 2 KHz with 200 femtosecond pulse duration at 775 nm wavelength. The other fs-laser installation is the ASUR system in the University of Marseille delivering 25 fs pulses at a repetition rate of 10 Hz. The irradiated spots were investigated using optical and scanning electronic microscopy to obtain the damage threshold of the deposited films versus the PLD growth conditions. The obtained results are compared to those reported in the literature and open the way to obtain optical layers for fs-laser mirrors possessing good LDT values by using the PLD technique. Acknowledgements The work presented was funded by Nucleu –INFLPR program and ELI 17/2017 project.

Authors : Iulian IONITA (1), Adrian BERCEA (2),(3), Simona BRAJNICOV (2),(4), Andreea MATEI (2), Valentin ION (2), Valentina MARASCU (1),(2), Bogdana MITU (2), Catalin CONSTANTINESCU (3)
Affiliations : (1) University of Bucharest, Faculty of Physics, RO-077125 Magurele (Bucharest), Romania (2) INFLPR - National Institute for Lasers, Plasma, and Radiation Physics, RO-077125 Magurele (Bucharest), Romania (3) IRCER (UMR 7315) - CNRS / University of Limoges, F-87068 Limoges, France (4) University of Craiova, Faculty of Sciences, RO-200585 Craiova, Romania

Resume : Thin films of pentacene, i.e. a polycyclic hydrocarbon consisting of five linearly-fused benzene rings, are grown on silicon and quartz (SiO2) substrates by matrix assisted pulsed laser evaporation (MAPLE) and by using toluene as a frozen matrix (melting point: −95 °C). The thin film samples are subsequently investigated for their optical, morphological and chemical structure, i.e. by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and spectroscopic-ellipsometry (SE). Due to its highly conjugated aromatic behaviour, pentacene exhibits semiconductor properties and has been shown to generate excitons upon absorption of ultra-violet (UV) or visible light. Here, we studied the ultrafast excited state dynamics of pentacene, in bulk and as thin films, after optical excitation by using femtosecond (fs) time-resolved second harmonic generation (SHG). A pulsed femtosecond Ti:sapphire laser (80 MHz repetition rate, 800 nm, 100 fs) was employed to demonstrate SHG potential of such polycyclic aromatic hydrocarbon simple molecule. The substrates used in studying the films are inert and non-interacting, known to deliver no noteworthy contribution to the SHG-signal. Therefore, the pure response of pentacene to the electronic excitation can be resolved in contrast to the measurements on SiO2. This study provides important insights on the excited states dynamics of pentacene, an essential step for understanding the photophysics of simple, linearly-fused arenes.

Authors : Ro.G. Nikov1, N.N. Nedyalkov1, D.B. Karashanova2
Affiliations : 1 Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, Sofia 1784, Bulgaria 2 Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences, G. Bonchev Street, bl. 109, Sofia 1113, Bulgaria

Resume : This study presents a methodology for the synthesis of one-dimensional colloidal nanostructures. The method consists of laser ablation of a ferromagnetic target (Fe) in a liquid medium carried out in the presence of an external magnetic field. Direct deposition of the ablated material is realized as a substrate was placed in the liquid. At certain experimental condition deposition of nanoparticle chains on the substrate can be realized. The ablation experiments were performed in two different liquids – ethanol and distilled water, as their role on the characteristics of the ablated material is clarified. The influence of different laser processing parameters and ablation geometry on the features of the nanostructures deposited on the substrate and these dispersed in the liquid were also investigated. On a basis of detailed analyses using Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy, and Transmission Electron Microscopy the morphology, composition, and size distribution of the fabricated nanostructures were studied. The optical properties of the produced colloids were also evaluated by optical transmittance measurements in the UV–VIS spectral range. The presented method allows fabrication of contamination-free nanostructures with potential application in biotechnology, catalysis, sensorics and magneto-optics devices.

Authors : L. Gavrila-Florescu1, C. Fleaca1, A. Tiliakos1, I. Morjan1, A. Ilie1, E. Dutu1, C. Mihailescu1, A. Marinoiu2, G. Prodan3, F. Dumitrache1
Affiliations : 1. National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., PO Box MG-36, Magurele, Ilfov, Romania 2. National Research and Development Institute for Cryogenic and Isotopic Technologies, ICSI Rm. Valcea, 4 Uzinei Street, Ramnicu Valcea, Valcea, Romania 3. Faculty of Mechanical, Industrial and Marine Engineering, “Ovidius” University, Mamaia Bd. 124, Constanta, Romania

Resume : With platinum established as the most commonly used electrocatalyst for the sluggish oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEM-FCs), its high demand and limited supply present an obstacle for the full commercialization of FC technology by raising the overall costs at non-competitive levels. Thus, considerable research efforts have been dedicated to doping nanocarbons with low-cost heteroatoms (e.g. N, B, P, S) proven to enhance catalytic activity, with less attention having been directed to iodine as a dopant. However, the volatility of iodine renders it an appropriate heteroatom donor in elemental or compound form as hydroiodic acid for laser pyrolysis: the application of high-powered lasers to homogeneous gas-phase media based on the resonance between the laser radiation and a gaseous photosensitizer. Laser pyrolysis constitutes a versatile method for the bulk production of fine powders with uniform and controllable particle size distribution and morphology. Using typical carbon donors, such as acetylene, and introducing iodine fumes into the precursor mixture leads to the production of iodine-doped core-shell nanocarbons. These are extensively characterized via spectrometric (Raman, XRD, XPS), thermogravimetric/adsorption (TGA, BET), and microscopy (SEM, HRTEM) techniques; their electrocatalytic performance is evaluated on dedicated PEM-FC testing stations.

Authors : P. Martinez(1); J. Gaudin(1); I. Papagiannouli(1); V. Blanchet(1); D. Descamps(1); B. Fabre(1); S. Petit(1); A. Lévy(2); J. Marthelot(3); N. Bernier(4); J.-B. Dory(4);P. Noé(4)
Affiliations : (1) CEntre Lasers Intenses et Applications, 43 rue Pierre Noailles, 33405 Talence, France (2) Sorbonne Universités, CNRS, UMR 7588, Institut des Nanosciences de Paris, Cedex-05-Paris, 75252, France (3) Princeton, Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08540, United States (4) Univ. Grenoble Alpes, CEA, LETI, MINATEC Campus, F-38054 Grenoble, France

Resume : Functionalizing physical or chemical properties of surfaces is nowadays routinely achieved by means of light-matter interaction using laser beams. We present a way to generate random fingerprint-like patterns resulting from the surface melting of 500 nm-thick amorphous thin films of Ge-Sb-Te chalcogenide alloys covered by a 10-nm thick SiN capping layer after exposition to different laser pulses (30 fs 800 nm Ti:Saph, 400 fs and 400 ps Yb fiber 1030 nm) in the µJ range energy. The patterns were investigated by AFM and optical phase contrast microscopy. The spatial frequency of the obtained wrinkles is determined to be on the μm-1 scale. The latter is related to the thickness of the melted layer of material which depends on the laser fluence (in the tenth of mJ/cm2 range); the higher the intensity, the thicker the layer and the smaller the spatial frequency. The origin of the physical mechanism at play here is clearly different from so called laser induced periodic surface structure (LIPSS) patterns. Further HR-TEM measurements indicate that the irradiated layer of material is still amorphous, but seems to be made of a different amorphous phase than the pristine underlying one. A straightforward application of these patterns is to use them as anti-counterfeiting tags. We show as well how a neuron based algorithm is able to unambiguously retrieve a pattern among a test samples to 100.

Authors : L.N. Dumitrescu1, A. Vlad1*, R. Birjega1, A. Matei1, M. Dinescu1, R. Zavoianu2, M. Secu3, V. Raditoiu4, M.C. Corobea4
Affiliations : 1National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 077125 Bucharest, Magurele, Romania 2University of Bucharest, Faculty of Chemistry, Department of Chemical Technology and Catalysis, 4-12 Regina Elisabeta Bd., Bucharest, Romania 3National Institute for Materials Physics, P.O. Box MG-7, 77125 Bucharest-Magurele, Romania 4RomaniacNational R.&D. Institute for Chemistry and Petrochemistry, ICECHIM, 202 Splaiul Independentei Str., CP-35-274, 060021 Bucharest, Romania

Resume : Nowadays stimuli-responsive materials have received increasing interest due to their potential applications in smart systems, sensors, printed or stamped elements. Here, we report on the fabrication of a photochromic thin films using Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. Two types of photochromic dyes were used: an organic pigment with a spirooxazine structure encapsulated in an appropriated organic resin and an AZO organic dye intercalated in an inorganic layered double hydroxide (LDH). The nanocomposites were transferred by UV laser (266 nm) on different substrates: Si (001), polyamide and flexible transparent polymers. Water, ethanol were used as solvents for the preparation of the targets for MAPLE experiments. The optical, structural, morphological and photochromic properties of the as deposited films revealed the role guest chromophores and of the host matrix either resin or LDH.

Authors : C. Carraro(1,2), R. Milazzo(1,2), F. Sgarbossa(1,2), G. Maggioni(1,2), W. Raniero(2), S. Carturan(1,2), D. Scarpa(2), L. Baldassarre(3), M. Ortolani(3), A. Ballabio(4), G. Isella(4), S. Modak(5), L. Chernyak(5), A. Andrighetto(2), D.R. Napoli(2), D. De Salvador(1,2) and E. Napolitani(1,2)
Affiliations : (1) Dipartimento di Fisica e Astronomia, Università di Padova, Via Marzolo 8, I-35131 Padova, Italy; (2) Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, Viale dell’Università 2, 35020 Legnaro (PD), Italy; (3) Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Rome, Italy; (4) Dipartimento di Fisica, L-NESS, Politecnico di Milano, Polo di Como, Via Anzani 42, I-22100 Como, Italy (5) Department of Physics, University of Central Florida, Orlando, FL 32816 USA

Resume : The fabrication of highly doped and high quality Ge layers is currently a challenging hot topic in nanoelectronics, photonics and radiation detectors, particularly regarding n-type doping. In this matter, dopant deposition followed by pulsed laser melting (PLM) has demonstrated to be a simple and cheap doping method, with a thermal budget lower than other methods commonly used and, at the same time, able to achieve record activation levels with no residual damage and excellent electrical and optical properties relevant for Ge future advanced devices. Ge samples with a n-type dopant Sb sputtered on the surface have been treated with PLM using a 7 ns, 355 nm Nd:YAG solid status laser or a 25 ns, 248 nm KrF excimer laser. A broad characterization has been performed, based on secondary ion mass spectrometry, channeling-Rutherford backscattering spectrometry, single and differential Van der Pauw-Hall, high resolution x-ray diffraction, infrared reflectivity. We show that PLM promotes an efficient diffusion of high Sb concentrations in the Ge melted subsurface layer followed by fast epitaxial regrowth, leading to samples with exceptional crystalline quality and active concentrations well above 1e20 cm^-3. Key properties such as substitutional fraction, electron mobility, residual strain, infrared reflectivity and plasma frequency are also characterized and discussed.

Authors : M. Jalili 1, H. Ghanbari 2, R. Malekfar 1
Affiliations : 1 Atomic and Molecular Physics Group, Department of Physics, Faculty of Basic Sciences, Tarbiat Modares University, Tehran, P.O.Box 14115-175, I.R. IRAN 2 School of Metallurgy & Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran, Iran

Resume : Laser as a source of radiation is a versatile form of energy with a various range of application. In this research, liquid-phase pulse laser ablation (LP-PLA) was used to produce graphene nano-sheets. For this purpose flexible graphite have been exfoliated in four different solvents by employing 1064 nm laser wavelength using 70 mJ/pulse energy. They were then characterized using X-Ray Diffraction Pattern (XRD), acetone was selected as a desired liquid medium, and afterward, the morphological and structural studies of graphene nano-sheets prepared by LP-PLA method in acetone medium was done by Field Emission Scanning Electron microscopy (FESEM), UV-Vis-NIR and Raman spectroscopy. In addition, it is found that increasing the energy of laser pulses to 120 mJ/pulse in acetone as the liquid environment, leads to the formation of undesired nanoparticles remained on the surface of the graphene nano-sheets. Also, pinned graphene-nano-sheets on the surface target was demonstrated by FESEM analysis.

Authors : F. Zacharatos, K. Andritsos, I. Theodorakos, I. Zergioti
Affiliations : National Technical University of Athens, Physics Department, Iroon Polytehneiou 9, 15780, Zografou, Athens, GR

Resume : The field of flexible and stretchable electronics has evolved very rapidly over the past 10 years, enabling unprecedented innovations in consumer electronics and sensors. As the demand for miniaturization and power of flexible devices increases, so does the need for novel manufacturing processes and materials, but also for technologies addressing the fabrication of reliable and durable interconnections under large mechanical stress and small bending radii. Laser Induced Forward Transfer (LIFT) of metal nanoparticle and nanowire inks, has emerged as a key-enabling technology for flexible electronics. In this paper, we demonstrate how this technology can also be applied for achieving high resolution flexible interconnections, with form factors in the order of 10 micrometers. In particular, we have employed different Ag nano-inks in terms of nanoparticle size and various flexible substrates such as PEN and PDMS for the validation of the performance of these interconnections: an all-laser fabricated flexible platform comprising Ag microelectrodes has been developed for test cycles of bending at radius < 1cm and stretching. Moreover, emphasis has been given on the study of electro-migration of Ag, a phenomenon occurring when Ag atoms diffuse under high current densities. For test structures comprising Ag nanoparticles, we have conducted acceleration stress tests in order to shed light on the effect of nanoparticle size and substrate (joule heating) on the electro-migration process.

Authors : Linda Pabst, Robby Ebert, Horst Exner
Affiliations : Laserinstitute Hochschule Mittweida

Resume : Silicon wafers with a passivation layer of silicon dioxide are a commonly used substrate in micro technology especially in microelectronic. Besides lithography, laser processing obtains an increasing role in the processing of such microelectronic devices. The laser is used to separate functional structures or partially remove the passivation layer. Ultra-short pulse laser increase the processing quality, precision and can achieve a higher selectivity compared to longer pulse durations. The knowledge of the ablation behaviour of the SiO2 layer is essential to avoid damage to functional structures by the laser processing of microelectronic devices. Therefore, the selective ablation of a 100 nm thin silicon dioxide layer on silicon substrate was investigated using an ultra-short pulse laser with a wavelength of 1028 nm. The influence of the pulse duration, in the range between 200 fs and 10 ps, on the ablation process was examined. Single and multiple pulses ablation thresholds of the SiO2 layer were determined and the corresponding incubation coefficients calculated. Optical, scanning electron and atomic force microscopy were used to characterize the irradiation area. As a result, different ablation morphologies were observed, dependent on the processing parameters. These results were applied to realize simple structures by selective ablation of the SiO2 layer.

Authors : E. Dutu1, M. Scarisoreanu1, A. Ilie1, F. Dumitrache1, C. Fleaca1, L. Florescu-Gavrila1, I. P. Morjan1, A. Tiliakos1, A. Badoi1, A-M. Banici1, A. Smarandache1, E. Tanasa2
Affiliations : 1 National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania;; 2 Politehnica University of Bucharest, Bucharest, Romania

Resume : In this work we prepared carbon nanostructures doped with halogen by laser pyrolysis method, starting from tin precursor - SnCl4 and ethylene / DMDS. The inert gas (Ar) was used to confine and cool the nanoparticle species from reaction. The study of the effect of the synthesis parameters on the resulting nanoparticles morphology and structure was made by X-ray diffraction (XRD), electronic transmission microscopy (TEM), electronic scanning microscopy (SEM), spectroscopy (EDS) and optical spectrometry (UV-Vis). The results of these studies will be useful in optimizing the synthesis of halogen doped carbon nanostructures and determine the parameters appropriate to the desired result, regarding efficient energy generation.

Authors : L. Rusen1, L. E. Sima2, A. Bonciu1,3,I. Anghel1, V. Dinca1, and M. Dinescu1
Affiliations : 1National Institute for Lasers, Plasma and radiation Physics, Bucharest, Romania 2Institute of Biochemistry of the Romanian Academy IBAR, Bucharest, Romania 3University of Bucharest, Faculty of Physics, Bucharest, Romania

Resume : The design and processing of instructive surfaces with synergic mechanical, chemical or topographical properties capable of directing cell behaviour represents both the main challenge and the main strategy to guarantee the long-term success of a biomedical device or implant. Nevertheless, the design must take in consideration the correlation between cell type, material characteristics and the specific function to be accomplished for the aimed application. In this work, laser processing of micro-structured biomaterials ( i.e ceramics) with convex and concave topographies for evaluating the role of materials surface topography on Mesenchymal Stem Cells-MSCs responses are presented. Ti Saphire fs laser was used to obtain optimized architectures of zirconia ceramics. All the surfaces were analysed by Atomic Force Microscopy and Scanning Electron Microscopy and the contact angle measurements revealed a direct correlation between the material type and morphology with Mesenchymal stem cells response. The physico-chemical characteristics of the microstructured surfaces, along with the in vitro analyses, suggest that our designed biointerfaces represent an efficient way to tackle the design of implant surfaces or smart interfaces for wide range of biomedical applications. Acknowledgment: Financial support from Nucleu Program 2019 is acknowledged.

Authors : A.F. Bonciu1,2, A. Palla-Papavlu1, V. Dinca1, M. Filipescu1 and M. Dinescu1
Affiliations : 1) National Institute for Lasers, Plasma and Radiation Physics, Magurele, Bucharest, 077125, Romania; 2) University of Bucharest, Faculty of Physics, RO 077125, Magurele, Romania; *Corresponding author:

Resume : Chemical sensors and biosensors are the main components in products designed for healthcare monitoring systems as they are attractive competitors of the bulky, expensive, and complex analytical instruments currently used in medical applications. However, recent estimates show that the biosensor and electrochemical sensor market are dominated by glucose sensors. Therefore, there is a great need to expand the application of biosensors beyond glucose. Even more, taking into account the rapid development of the society’s needs, concepts such as intelligent clothing and wearable devices receive increasing attention. In addition, new features such as portable, flexible, and real-time monitoring become more and more important. In the last years, recent approaches are focused on wearable electrochemical sensors, which can detect target analytes (i.e. a variety of heavy metals) in saliva, tears, sweat, and interstitial fluid. The aim of this work is the development of an original flexible and wearable biosensor based on nanocomposite materials (polymers and graphene) fabricated by laser-induced forward transfer. In particular we focus on the synthesis of donor materials and the optimization of the LIFT process for obtaining reproducible pixels which are used as electrodes for the electrochemical biosensors. We printed different polymer:graphene nanocomposites onto flexible substrates (coated with an insulating layer, for ex. Parylene C, which prevents electrical contact with the body fluids). The biosensors fabricated by LIFT are used for the detection of heavy metals in human body fluids. Promising results i.e. high sensitivity and detection limits were obtained, which proves LIFT as an alternative method for printing nanoscale materials aiming at the fabrication of wearable sensors. Acknowledgement Financial support from i) NILPRP through the NUCLEU program and ii) UEFISCDI, though the “Smart flexible biosensor via laser transfer for body fluids monitoring (iFLEX)” project are gratefully acknowledged.

Authors : A. Petris1, C. Vasiliu2*, S. Mei3#, J. Yang3, S. Etemadi4 , R. Wendelbo4, P. Gheorghe1, L. Ionel1, L. Rusen1, A. M. Iordache1, M.Elisa1
Affiliations : 1.National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Str., Magurele, Romania; 2.National R&D Institute for Optoelectronics – INOE 2000, 409 Atomistilor Str., Magurele, Romania; 3. 4. Abalonyx AS, Forskningsveien 1, 0373 Oslo, Norway

Resume : Lasers are currently indispensable for many civilian and military applications and there is a considerable need to develop optical limiting materials for laser damage prevention of optoelectronic devices and for people protection. Specific to an optical limiting material is the linear increase of the transmitted power/fluence of the laser beam when the incident one is increasing, below a threshold, while above the threshold the transmitted power/fluence remains constant, independently of the power/fluence of the incident laser beam. The optical limiting capability of several synthesized reduced graphene oxide (rGO) based materials, as films, organic/inorganic solutions, and silico-phosphate composite materials have been investigated by intensity scan at different wavelengths and temporal regimes of excitation: fs pulses at 1550 and 775 nm, ns pulses at 1064 nm. The experimental transmittance has been determined in all performed experiments. The value of the optical transmittance, in the linear regime, and the saturation intensity of the nonlinear transmittance curves, where applied, have been determined. The laser induced damage in the synthesized materials, under the action of laser beams, was also investigated. Our results evidenced the influence of the “matrix” that embed the rGO. The influence of rGO concentration and of P2O5, in silico-phosphate matrix, on optical limiting potential was discussed. Acknowledgements: MANUNET Program, Project MNET17/NMCS-0114, OLIDIGRAPH

Authors : M. Socol1*, N. Preda1*, C. Breazu1, A. Costas1, O. Rasoga1, A. Stanculescu1, G. Popescu-Pelin2, G. Socol2
Affiliations : 1National Institute of Material Physics,405A Atomistilor Street, PO Box MG-7, 077125, Bucharest-Magurele, Romania 2National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-36, 077125, Bucharest-Magurele, Romania

Resume : Hybrid organic-inorganic thin films based on zinc phthalocyanine (ZnPc) and ZnO nanoparticles were deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE). Synthesized by a simple wet chemical precipitation method, the ZnO nanoparticles were featured by hexagonal wurtzite structure, band-gap value at ~3.3 eV and emission bands typical for this semiconductor. The organic (ZnPc) - inorganic (ZnO) hybrid films were obtained by MAPLE involving the following experimental conditions: dimethylsulphoxide (DMSO) as solvent, 350 mJ/cm2 laser fluence, 40 000 number of laser pulses and 5 cm target-substrate distance. The properties of the hybrid films containing ZnO nanoparticles in various amounts were evaluated by a complex characterization. Thus, scanning electron microscopy confirms the presence of the ZnO in the prepared hybrid films. No chemical decomposition of the pristine organic and inorganic compounds was observed in the FTIR spectra. The optical spectra recorded on MAPLE films disclose the signature of the raw materials (ZnPc and ZnO). The current-voltage (I-V) measurements carried out in dark and under illumination reveal the influence of the ZnO nanoparticles amount on the electrical properties of the hybrid films. Our study provides new insight in the MAPLE deposition of the organic-inorganic hybrid films which can find applications in the photovoltaic cells area.

Authors : A.Stanculescu1, C.Breazu1,4, M.Socol1, O.Rasoga1, N.Preda1, T.Ivan2, A.M.Solonaru2, M.Grigoras2, F.Stanculescu 3, G.Socol 4, M.Girtan5
Affiliations : 1National Institute of Materials Physics, 405A Atomistilor Street, P.O. Box MG-7, Bucharest-Magurele, 077125 Romania,; 2P. Poni Institute of Macromolecular Chemistry, 41 A Gr. Ghica Voda Alley, 700487-Iasi, Romania; 3University of Bucharest, Faculty of Physics, 405 Atomistilor Street, P.O. Box MG-11, Bucharest-Magurele, 077125 Romania; 4National Institute for Laser, Plasma and Radiation Physics, Str. Atomistilor, Nr. 409, PO Box MG-36, Magurele, Bucharest, 077125, Romania; 5Laboratoire LPHIA, Université d’Angers, LUNAM, 2 Bd. Lavoisier 49045, Angers, France

Resume : The main limitations of the organic devices’ performances come from the low mobility of the charge carriers, reduced diffusion length of exciton and reduced interfacial contact area between the donor and the acceptor compound. The synthesis of new organic semiconductors and development of new device configurations represent alternatives for obtaining an efficient charge carriers transport and devices with improved performances. This paper presents some studies of the organic heterostructures realized in both bi-layer and mixed layer configurations on flat and patterned glass covered by ITO substrates by Matrix assisted pulsed laser evaporation/MAPLE (solvent=chloroform, fluence=300 mJ/cm2, number of pulses=15000). A start-shaped arylenevinylene compound was used as donor and perylene tetracarboxidiimide, a non-fullerene compound, as acceptor. The glass substrate was covered by a grating of nanostructures developed by UV-Nanoimprint Lithography characterized by a cylindrical shape, periodicity=1.1 m, diameter=400 nm, depth~300 nm. The ITO electrode has been subsequently deposited on this nanostructured surface by Pulsed Laser Deposition (fluence=1.2 J/cm2, number of pulses=7000, p_oxygen=1.5 Pa). SEM and AFM measurements have evidenced the influence of the ITO electrode nano-patterning on the morphology of the organic layer deposited by MAPLE. The effect of the periodically array of (nano)structures on the optical and electrical properties of the heterostructures with bi-layer compared to the heterostructure with mixed layer has also been analyzed.

Authors : A. Daskalova1, I. Bliznakova1, L. Angelova1, A. Carvalho 2, 3, 4, A. Trifonov 5, C. Nathala 6, H. Declercq 7, F. Monteiro 2, 3, 4, I. Buchvarov 5
Affiliations : 1 Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee Blvd., 1784, Sofia, Bulgaria; 2 i3S - Instituto de Investigação e Inovação em Saúde, U. Porto, Porto, Portugal; 3 INEB - Instituto de Engenharia Biomédica, U. Porto, Porto, Portugal; 4 Faculdade de Engenharia, Departamento de Engenharia Metalúrgica e Materiais, U. Porto, Porto, Portugal; 5 Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 James Bourchier Blvd., 1164, Sofia, Bulgaria; 6 High Q lasers Gmbh, Spectra Physics, 9 Feldgut, 6830 Rankweil, Austria; 7 Department of Basic Medical Sciences, Ghent University, De Pintelaan 185 6B3, 9000 Gent, Belgium

Resume : Bioceramic scaffolds have been widely used as templates for cell adhesion, proliferation, and differentiation thus promoting tissue regeneration. However, their brittleness, constrains application in tissue engineering. The most common bioactive materials that are used in bone and dental tissue engineering are zirconia (Zr), hydroxyapatite (HAp) and calcium phosphates ceramics (CaP). Zirconium possess suitable mechanical properties, but its inertness is a big challenge to develop a scaffold with excellent bioactive characteristics. On the other hand, polymers can be easily fabricated into complex shapes and porous structures. Thus, a combination of bioceramics with biodegradable polymers is employed to achieve better biological features. In this study we have employed femtosecond laser texturing for surface processing of zirconia ceramics and its blends with biopolymers. Altering morphology and roughness of Zirconium based ceramics is an effective way of improving its adhesive properties. In this study, femtosecond Ti: sapphire laser was selected to provide treatment of chitosan/hydroxyapatite thin films reinforced by nano ZrO2 (CH/HAp/ZrO2) at different ratios and Alumina Toughened Zirconia (ATZ) ceramics. SEM analysis of produced microstructures demonstrated creation of surface modification in the form of stripes, evenly distributed with well-defined boundaries resulting in increased effective surface area of the sample. EDX analysis revealed that the typical elements for CH/ HAp/ZrO2 and ATZ were preserved after laser treatment. The ability of the patterns to enhance adhesion and orientation of MC3T3 osteoblasts and adipose derived (ADSC) stem cells, as measured by fluorescence microscopy imaging, due to changes in surface morphology, were assessed. The obtained results suggest that femtosecond laser treatment offers a fast and promising approach to introduce controlled topography at the micrometric scale by creating a path for optimization of ceramic scaffold surface properties.

Authors : A. Matei, A. Vlad, R. Birjega, M. D. Ionita, E. R. Ionita, V. Marascu, A. Lazea-Stoyanova
Affiliations : National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, 077125 Magurele, Romania

Resume : Montmorillonite (MMT) is lamellar clay material, part of smectite group of phyllosilicate mineral species. Montmorillonite has an interesting lamellar structure allowing guest absorption between the lamellas. The absorption can take place at the surface, or interlayer. The aim of this work is to produce lamellar montmorillonite (MMT) thin films as active surfaces for the absorption of organic and inorganic pollutants from residual waters. Pulsed laser deposition (PLD) and matrix assisted pulsed laser evaporation MAPLE are the techniques employed for the deposition of montmorillonite thin films. The deposition parameters, especially the laser wavelength, substrate temperature and background deposition pressure, play an important role in the composition and morphology of the films. The chemical composition, crystalline structure, surface morphology of the MMT thin films were thoroughly investigated and crystalline films with good adhesion to the substrate and controllable thickness were obtained. The possible applications of the as deposited films, especially in electrochemical sensors, are presented and discussed.

Authors : José M. Zárate-Reyes, Oswaldo Sánchez-Dena, Alberto Peralta-Angeles, Erick Flores-Romero, Carlos A. Luna-Mayo, Cecilia Salinas, Juan-Carlos Cheang-Wong, Alejandro Reyes-Esqueda
Affiliations : José M. Zárate-Reyes; Oswaldo Sánchez-Dena; Alberto Peralta-Angeles; Carlos A. Luna-Mayo; Cecilia Salinas; Juan-Carlos Cheang-Wong; Alejandro Reyes-Esqueda; Instituto de Física, Universidad Nacional Autónoma de México, Cd. Universitaria, Coyoacan, Ciudad de México, 04510, México. Erick Flores-Romero; Catedrático CONACYT, Instituto de Física, UNAM, Ciudad de México, México.

Resume : Composites consisting of metallic nanoparticles (NPs) embedded in dielectric matrices have attracted considerable interest due to their possible applications in nonlinear optical devices such as optical computing, switching, real time holography, and phase conjugators. These composites may present large nonlinear optical response due to electronic transitions in the NPs. In this work, ordered arrays of plasmonic gold nanoparticles embedded in fused silica plates were produced by 2 MeV Au ion implantation at normal incidence through a lithographic mask, followed by a post-implantation annealing treatment. As lithographic masks we used monolayers of silica microspheres with three different sizes (590, 650 and 900 nm in diameter) onto quartz substrates and the implantation fluences ranged from 1E16 to 1E17 ions/cm2. A strong optical absorption band associated with the Localized Surface Plasmon Resonance (LSPR) was observed at 520 nm. The third-order nonlinear optical response of the samples was characterized by using the Z-Scan technique with a wavelength of 532 nm and a pulse duration of 26 ps.

Authors : Y.M. Andreeva-1, V.V. Koval-1, R.A. Zakoldaev-1, M.M. Sergeev-1, F. Vocanson-2, and T.E. Itina-1,2
Affiliations : 1-ITMO University, 49 Kronverkskiy pr., 197101, Saint-Petersburg, Russia 2-Laboratoire Hubert Curien, UMR CNRS 5516, UJM-Saint-Etienne, Univ. Lyon, Campus Manufacture, Saint-Etienne, France

Resume : We demonstrate a possibility of a controlled laser writing of well-organized arrays of silver nanoparticles (AgNPs) with a size of 10 nm in initially mesoporous SiO2 films (180 nm thickness). The films were fabricated by the sol-gel method and pre-doped with silver nitrate. The obtained metasurfaces consist of the ordered 2D structures with a period of Λ = 410 and 520 nm and a track width of ~150 μm. These structures were formed by a progressive laser scanning. Picosecond laser pulses (λ=355nm, τ=30ps, f=10Hz) were used. The beam profile was linearly polarized and transformed into a two-beam interference pattern. To obtain an interference pattern, a confocal optical system was used, where the function of a diffraction spreader was performed by a phase grating made on fused quartz using the laser-induced black-body heating method. The mechanisms of laser recording of the obtained structures are then examined. The processes, such as photochemical synthesis of AgNPs and formation of a film nanorelief, are shown to be involved. The optical properties of the plasmonic 2D metasurface were also investigated at different angles and directions of the incidence of natural light, as well as for both TE and TM polarized light. As a result, we observed and explained an increase in the plasmon resonance at λ = 486 and 520 nm and a change in the diffuse reflection depending on the direction of the incident light with respect to the periodic structure. These results are promising for photonics applications.

Affiliations : 1) National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor St, RO-077125, Magurele, Romania; 2)University of Bucharest, Faculty of Physics, 405 Atomistilor St, RO-077125, Magurele, Romania; 3) CNR-Instituto dei Sistemi Complessi, Via del Fosso del Cavaliere 100, I-00133, Rome, Italy

Resume : The non-lead piezoelectric materials with strong piezoelectric response are regarded as key materials for replacing Pb-based materials in functional devices. Lead-free (Ba1−xCax)(ZryTi1−y)O3 is a perovskite material which exhibits values of the piezoelectric coefficients similar or even superior to the hard PZT materials. Doping with Ca and Zr allows flexibility in the stoichiometry to be obtained, the tunability of the functional properties by varying the level or doping ratio being the main advantage. By incorporating the piezoelectric ceramic material BCTZ into the PVDF matrix, high-piezoelectric and flexible heterostructures can be obtained, which will allow incorporation of the pressure sensor device in various applications. Thin film of BCZT45 and PVDF/BCZT45 were deposited on Pt-kapton substrate by MAPLE technique. Thin films of BCZT45 on different substrates have been deposited by PLD for comparison purposes. Piezoforce microscopy measurements on PVDF/BCZT/Pt/Kapton films revealed high values of the d33 effective piezoelectric coefficient and good switching behavior, as shown by phase variation under electric field. The out-of-plane PFM response shows strong domain contrast, indicating that the material is polar with a polarization vector oriented mainly along the c-axis. The good piezoelectric properties of the PVDF/BCZT films indicate the possibility to employ these structures as piezoactive elements.

Authors : Alina Irina CĂLUGĂR1,2,Sorina IFTIMIE1, Adrian RADU1, Maria DINESCU2, Vlad-Andrei ANTOHE1, Lucian ION1, and Stefan ANTOHE,1,3,*
Affiliations : 1University of Bucharest, Faculty of Physics, 405 Atomistilor, P.O. BOX MG-11, 077125, Magurele, Ilfov, Romania 2The National Institute for Laser, Plasma & Radiation Physics (INFLPR), Atomistilor Street, No.409,Magurele city, Ilfov county, Postal code: RO-077125, Romania P.O. Box MG-36 3Academy of Romanian Scientists, 54 Splaiul Independentei, 030167, Bucharest, Romania Corresponding author:, phone: +4021 4574535, fax: +4021 4574418, 405Atomistilor, P.O. BOX MG-11, 077125, Magurele, Ilfov, Romania

Resume : Organic photovoltaic cells (OPV) present big interest due to their specific properties as mechanical flexibility, light weight, ease to process and low cost fabrication. The organic semiconductors are very good absorbers (absorption coefficients>105cm-1) and their photogeneration mechanism is an excitonic one. Taking into account that the diffusion length of exciton in organic materials is smaller than 80 nm, the bulk heterojunction configuration resulting from the blend of a Donor and an Acceptor molecules, such as P3HT:PCBM, seems to be a promising way to obtain performant OPVs. Unfortunately, the P3HT:PCBM polymeric blend is unstable in light interaction and exhibits a different behavior when mixed and deposited layer-by-layer, so solvents should be carefully chosen. For this reason we use for deposition of polymers two techniques: MAPLE (Matrix Assisted Pulsed Laser Evaporation) and spin-coating. First technique allows the polymer to be deposited regardless of the chosen solvent. The proposed configuration of our structures is IZO-5nm/Ti/SnO2 nanoparticles/PEDOT:PSS/P3HT-PCBM-Si:PCPDTBT/ZnO/Ag, in which a low band gap polymer, e.g. poly[2,1,3-benzothiadiazole-4,7-diyl[(4,40-bis(2ethylhexyl)dithieno[3,2-b:20,30-d]silole)-2,6-diylalt-(2,1,3-benzothiadiazole)-4,7-diyl], (Si-PCPDTBT), is added to increase the number of photons harvested from solar spectrum and also to improve the stability. Acknowledgements: The study was supported by project 40PCCDI/2018, funded by UEFISCDI.

Authors : M. E. Koleva1, N. N. Nedyalkov1, Ru. Nikov1, Ro. Nikov1, V.I. Nuzhdin2, V.F. Valeev2, Y.N. Osin2, A.L. Stepanov2
Affiliations : 1Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd., Sofia 1784, Bulgaria; 2Kazan Physical-Technical Institute, Russian Academy of Sciences, 420029, Kazan, Russia

Resume : The composite Ag/ZnO nanostructures are fabricated by combining the laser and ion implantation techniques. The ZnO thin films are grown by pulsed laser deposition (PLD). The Ag+-ion implantation technique is used for surface embedding the silver nanoparticles in the ZnO thin film matrix. The implanted samples are also laser annealed by Nd:YAG laser at 355 nm and 532 nm at different laser fluences and number of laser pulses. The proposed structures are examined as SERS substrates, and the results are considered with respect to their microstructure, composition and optical properties. The heterostructures of optical transparent semiconductors and noble metal nanoparticles attract grate attention, as a higher SERS effect could be achieved due to contributions from both the electromagnetic enhancement, excited by the LSPR (localized surface plasmon resonance) of noble metal nanostrustures and the semiconductor supporting chemical enhancement, caused by the charge transfer between the noble metal and semiconductor. The effect of surface topography on SERS response is investigated. The properties of implanted nanostructures before and after the laser annealing are studied by SEM (scanning electron microscopy), AFM (atomic force microscopy), XPS (X-ray photoelectron spectroscopy) and UV-VIS spectroscopy. This paper provides a relation between the nanoscopic features of the prepared Ag/ZnO nanocomposites and their effectiveness as SERS active substrates. Acknowledgements: This work is financially supported by the Bulgarian National Science Fund under the Russian-Bulgarian bilateral project DNTS/Russia 02/3 – 14.06.2018 “Combined laser and ion implantation techniques for nanostructuring of Ag/ZnO composites for SERS applications”; in Russia - RFBR grant No. 18-58-18001.

Authors : E. Cantelar (1), G. Lifante (1), L. Grima (2), J.I. Peña (2), D. Sola (3)
Affiliations : (1) Departamento de Física de Materiales, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain; (2) Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-CSIC, Dpto. Ciencia y Tecnología de Materiales y Fluidos, 50.018 Zaragoza, Spain; (3) Laboratorio de Óptica, Centro de Investigación en Óptica y Nanofísica Universidad de Murcia, Campus Espinardo, 30.100 Murcia, Spain;

Resume : The incorporation of trivalent rare-earth ions in a glass matrix allows developing active optical devices such as laser, IR-to-visible up-converters, optical amplifiers, phosphors, thermometry, etc. Among the large variety of matrix composition studied, the most noteworthy are calcium silicate, calcium alumino-silicate and magnesium alumino-silicate glasses due to their excellent physical properties, which beside their ability to incorporate high concentration of rare-earth active ions, have led to various applications in solid state lasers, optical waveguides, luminescence probes, and even in medicine as in vivo radiation delivery vehicles for cancer treatment of internal organs. In this work, the energy transfer processes between Er3+ and Yb3+ ions in Ca3Al2Si3O12 and Mg3Al2Si3O12 glasses have been characterized by using several samples containing a fixed Er3+ concentration (0.5 mol%) and variable Yb3+ concentration (0.1, 0.5, 1 and 2 mol%). A relationship between the energy transfer parameters was established under selective Er3+ excitation at 800 nm (4I15/2 -> 4I11/2 absorption band) by using a Ti:Sapphire laser. Additionally, the dynamics of the resonant infrared levels (4I13/2 (Er3+):2F5/2 (Yb3+)) together with the dominant erbium emitting manifolds (2H11/2:4S3/2 and 4I13/2) have been investigated under pulsed excitation at 532 nm (4I15/2 -> 2H11/2 absorption band) using the second harmonic of a pulsed Nd:YAG laser. The use of both Er3+-pumping schemes, CW and pulse excitation, has allowed the full quantification of the macroscopic transfer and back transfer coefficients Finally, these macroscopic parameters have been used to establish a rate-equation model that allows to describe the dynamics of Er3+/Yb3+ co-doped alumino-silicate glasses.

Authors : D. Sola (1), J.R. Vázquez de Aldana (2), P. Artal (1)
Affiliations : (1) Laboratorio de Óptica, Centro de Investigación en Óptica y Nanofísica, Universidad de Murcia, 30100 Murcia, Spain; (2) Aplicaciones del Láser y Fotónica, University of Salamanca, 37008 Salamanca, Spain;

Resume : In this work the fabrication of diffraction gratings by femtosecond laser inscription in poly-hydroxyethyl-methacrylate and silicone hydrogel polymers used as soft contact lenses is reported. Linear diffraction gratings were inscribed by focusing the laser radiation 100 µm underneath the surface of the samples. As laser sources low- and high-repetition-rate Ti:sapphire laser with a pulsewidth of 120 fs working at 1 kHz and 80 MHz were used. Periodic patterns were produced by the variation of the pulse energy as well as the distance between tracks and scanning speed. Compositional and structural modifications on the materials were studied by means of micro-Raman spectroscopy. Far-field diffraction pattern was characterized under illumination of a continuous-wave He-Ne laser at 632.8 nm. First- and second-order efficiency as well as total efficiency were assessed. Finally, refractive index changes induced in the processed areas were evaluated to determine the processing conditions at which the modification was the optimal.

Authors : D. Abdelkader, F. Antoni, M. Kanzari,‎
Affiliations : Université de Tunis ElManar, Ecole Nationale d’Ingénieurs de Tunis, Laboratoire de Photovoltaïque et Matériaux Semiconducteurs, BP37, 1002 Le Belvédère, Tunis, Tunisia ‎ICube-Laboratoire des Sciences de l’Ingénieur, de l’Informatique et de l’Imagerie, Université de Strasbourg-‎CNRS, 23, rue du Loess, 67037 Strasbourg Cedex, France

Resume : Sodium doped CuInS2 materials (CIS:Na) was synthesized by a solid-state reaction using ‎earth-abundant copper, indium and sulfur elements. Sodium was used as dopant element (0.1, ‎‎1 and 3 wt %). The thermal evaporation technique was used to prepare CIS:Na thin films. ‎Then, the films were irradiated at room temperature in ambient air using a KrF excimer laser ‎with ‎a wavelength 248 nm. The irradiation was performed under laser energy density of 50 ‎mJ/cm2. ‎The Raman and XRD characterization revealed the amorphous character of the films ‎due to the porous behavior shown by the confocal microscopy. A strong change of the surface ‎morphology of the films was observed and it depends on the Na weight percent doping. ‎Optical constant were calculated from transmittance T and reflectance R spectra using a ‎special MATLAB program. CIS:Na thin films exhibit high absorption coefficients (104 - 2×105 ‎cm-1) in the visible range and the higher values were obtained for 3 wt % and it has the highest ‎Surface Energy Loss Function (SELF) values. The direct band gap (Eg dir) was in the range ‎‎1.61-2.06 eV. The refractive indices show an anomalous behavior in the optical gap region. ‎The CIS:Na 3 wt % sample exhibits a lower refractive index. All the dispersion curves of ‎refractive index were analyzed using Wemple-DiDomenico model. The real dielectric constant ‎and relaxation time were calculated.‎

Authors : L. Nedelcu, G. Annino*, C. Chirila, L. Trupina, A. C. Galca, M. G. Banciu
Affiliations : National Institute of Materials Physics, Bucharest-Magurele, Romania, *Istituto per i Processi Chimico-Fisici, IPCF-CNR, Pisa, Italy

Resume : Ba0.6Sr0.4TiO3 (BST) ferroelectric thick films were grown on single-crystal MgO substrates by using pulsed laser deposition (PLD) method. A KrF excimer laser, emitting at 248 nm wavelength with a fluence of 2 J/cm2 and repetition rate of 5 Hz, has been used. Structural, morphological, optical, and terahertz characterization of the BST films were performed by X-ray Diffraction, Scanning Electron Microscopy, Atomic Force Microscopy, Spectroscopic Ellipsometry (SE), and Terahertz Time-Domain Spectroscopy (THz-TDS). As a result of a parametric study, single-phase samples with appropriate microstructure were achieved. SE was employed to extract the thickness and optical properties by using a 3-layer optical model (substrate / thin film / roughness). The inferred refractive index @630nm is approximately 2.07, while the optical interference is visible until 3.3 eV. The THz-TDS measurements in transmission set-up were carried out one after the other on substrates before and after the BST film deposition. The standard THz-TDS analysis of double-layer samples proved difficult to complete in the cases in which a thin or thick film is deposited on a much thicker substrate of known dielectric properties. The effect of the film on the propagation of the electromagnetic wave is usually weak and often obfuscated by spurious effects, with the result of inconsistent values for the dielectric quantities. Nevertheless, we have been able to extract the complex dielectric permittivity in THz domain for BST samples with thicknesses higher than 2 micrometers, by developing a specific procedure of data analysis. Acknowledgments: This work was supported by a grant of Ministry of Research and Innovation, CNCS - UEFISCDI, project number PN-III-P1-1.1-TE-2016-1711, within PNCDI III”.

Authors : V. Ion, N. D. Scarisoreanu, A. Andrei, N. Enea, F. Andrei, A. Moldovan, A. Bonciu and M. Dinescu
Affiliations : National Institute for Laser, Plasma and Radiation Physics, Magurele, Bucharest, Romania

Resume : Microwave antenna developed for space industry must be able to operate in harsh environments where the radiation dose and temperature gradients are high. In order to protect these electronic devices, various coating techniques and materials were developed. Pulsed laser deposition (PLD) coatings allow the deposition of different materials on the microwave antenna for shielding it from the outer space harsh conditions. In this work we report the obtaining of multilayer structures for electronic devices protection in space environments. For this purpose, the heterostructures of Al2O3/Y:ZrO2 were deposited by PLD on microstrip coplanar antenna. The frequency response of microwave antenna was measured before and after deposition of heterostructure. The crystalline and morphologic properties of the coatings were studied by X-ray diffraction and atomic force microscopy (AFM) techniques. The optical properties and the thicknesses of layers were investigated by spectroscopic ellipsometry (SE). The dependence of optical constant with temperature was determined by SE in the 23-3000 C range of temperature. Acknowledgements: This work was supported by a grant of the Ministry of National Education and Scientific Research, RDI Programe for Space Technology and Avanced Research - STAR, project number 168/20.07.2017

Authors : Yao Wang Yong Li Zongren Xing Duo Tang Liang Wang
Affiliations : Institute of chemical materials, CAEP

Resume : Film is a widely used material in all kinds of fields. In weapon research field, it is used as ablation layer of the laser slapper detonator which has attracted attention due to high anti-electromagnetic interference, high-resolution timestamp and high safety. The energy transformation of the laser slapper detonator is “laser energy-heat energy-flyer kinetic energy”. In the process, the ablation layer play an important role in absorbing laser energy and transforming laser energy to heat energy. Several kinds of materials are used as ablation layer, among which reactive multilayers are new and has the potential to improve plasma performance induced by pulsed laser. In this study, Al/NI based reactive multilayers with two different modulation periods were integrated into ablation layer using magnetron sputtering technology. The structure and chemical composition of Al/Ni multilayers were confirmed by transmission electron microscopy. The effects of the Al/Ni multilayers on the plasma properties induced by pulsed laser were systematically investigated in terms of the electron temperature and density using laser-induced breakdown spectroscopy. Measurements of the plasma expansion velocity were performed using ICCD systems. It is found that the electron temperature and density has a relative to modulation period of Al/Ni multilayers, which is much higher than Al or Ni layer alone. The laser induced plasma expansion velocity is consistent with that found using electron temperature. Thus the conclusion that the ablation layer of Al/Ni reactive multilayers exhibited a high level of plasma and promoted laser induced plasma energy efficiency.

Authors : Wang Liang, Wang Zhihao, Tang Duo
Affiliations : Institute of Chemical Materials

Resume : Boron and potassium nitrate composites (B/KNO3) is one of the most widely used pyrotechnics for laser ignition applications. As main components of B/KNO3, boron and potassium nitrate serve as fuel and oxidizer, respectively, with trace additives mostly function as binder. Compared with other fuels, boron owns the highest volumetric energy density. However, the oxide layer (B2O3) on its surface will hinders its combustion and ignition, which have limited the application of boron in practical utilizations. Therefore, enhancing the combustion and ignition performance of B/KNO3 powders is valuable and significant. In this study. Carbon nano-tube aerogel loaded with boron and potassium nitrate (CABPN) energetic composite was prepared by ice template method. SEM images proved the micro structure of CABPN to be porous and nearly laminar. The Brunauer–Emmett–Teller (BET) specific areas of CABPN and BPN were 57.9 m2/g and 28.8 m2/g, respectively, indicating that the porous structure doubled the surface area, which is helpful for the reaction of combustion. Thermal-decomposition behavior of CABPN was studied by TG/DSC, and two consecutive exothermic peaks at around 410 ℃ and 460 ℃ were observed. Finally, a series laser ignition experiments were conducted and it was found that the boron content could regulate the laser ignition threshold of CABPN. Additionally, by loading Carbon nano-tube aerogel into B/KNO3, the ignition performance can be significantly enhanced.

Authors : Adrian BERCEA (1), Lucian TRUPINA (2), Liviu NEDELCU (2), Gabriel BANCIU (2), Laure HUITEMA (3), Aurelian CRUNTEANU (3), Frédéric DUMAS-BOUCHIAT (1), Corinne CHAMPEAUX (1), Catalin CONSTANTINESCU (1)
Affiliations : (1) IRCER UMR 7315 - CNRS / University of Limoges, Limoges, France (2) INFM - National Institute for Materials Physics, Bucharest, Romania (3) XLIM UMR 7252 - CNRS / University of Limoges, Limoges, France

Resume : Iridium thin films with a thickness varied between 20 and 100 nm are grown on MgO substrates with various crystallographic orientations by using by two different techniques, i.e. direct-current magnetron sputtering (DC-MS) and pulsed laser deposition (PLD). First, we present and discuss results on high resolution X-ray diffraction (XRD) and atomic force microscopy (AFM). Both types of analysis reveal that substrate temperature / annealing of up to 1200°C has significant effects on their structure and morphology, yet no effects are observed upon the electrical resistivity (~12 µΩ⋅cm) of the films, and no traces of iridium oxide are identified. High resolution transmission electron microscopy (HR-TEM) of the substrate-thin film interface show that iridium exhibits epitaxial growth with no diffusion effects. This aspect is challenging in electrode applications due to the difficulty in controlling phenomena occurring at the interfaces. Finally, we compare the advantages and disadvantages of each deposition technique, and present results with respect to their use as highly thermally resistant electrodes in tunable micro-capacitive components.

Authors : V. Dinca1, L.E. Sima2, M. Icriverzi2,3, A. Bonciu1,4, S. Brajnicov1, L. Rusen1, A. Roseanu2, A. Campean3 and M. Dinescu1
Affiliations : 1National Institute for Lasers, Plasma and radiation Physics, Bucharest, Romania 2Institute of Biochemistry of the Romanian Academy IBAR, Bucharest, Romania 3University of Bucharest, Faculty of Biology, Bucharest, Romania 4University of Bucharest, Faculty of Physics, Bucharest, Romania

Resume : For the application related to tissue engineering, implants, the controlled interfacial properties of materials and modulated behaviours of cells and biomolecules on their surface are important requirements. Roughness, chemistry and mechanics of biomaterials are all sensed by cells. Organization of the environment at the nano- and the microscale, as well as chemical signals, triggers specific responses with further impact on cell fate. Producing smart bio-interfaces with targeted functionalities represents the key point in effective use of hierarchically topographical and chemical bioplatforms. In this work, we present laser-based approaches (e.g. Matrix-Assisted Pulsed Laser Evaporation (MAPLE) and laser texturing used for the design of bio-interfaces aimed at controlling cell behaviour in vitro. Keywords: Bio-interfaces, laser processing, topography, protein-based coatings, stem cells

Authors : Han Huang, Lih Juann Chen
Affiliations : Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan, Republic of China

Resume : Nanolasers play an important role in transmitting messages with high speed, low energy loss and without interruption to each other when propagating in the same path. In this work, we report a semiconductor-insulator-metal (SIM) structure of ultraviolet nanolaser based on surface plasmon polariton (SPP) breaking through the diffraction limit. A gain medium of the single high crystallinity zinc oxide nanowire fabricating by chemical vapor deposition is crucial for laser operating at room temperature. The two-dimensional material, hexagonal boron nitride (hBN), which acts as the plasmonic nanocavity is prepared by mechanical exfoliation and is placed between a nanowire and the single crystal aluminum film. The SIM structure was found to exhibit higher optical intensity than the single nanowire without SPP effect. The high crystallinity of the hBN and the aluminum film are both the key factors to decrease the plasmonic losses when the light propagating at the interface between the dielectric layer and the metal substrate.

Authors : Chen Zhihui1, Vaishali Anandrao Sawant1, Monalisa Garai1, Hong Sheng Quah1,2, Jagadese J. Vittal1& Xu Qing-Hua1,2
Affiliations : 1. Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543; 2. NUS Graduate School for Integrative Sciences & Engineering (NGS), Singapore 117456.

Resume : Nonlinear optical materials with functions of generating second harmonic generation (SHG) or/and two photon photoluminescence (TPPL) have attracted great interest because of their applications in extending coherent light frequencies from the given lasers[1], biological imaging and photodynamic therapy[2]. Here we report on two metal–organic frameworks, namely, Bis{4-[2-(4-pyridyl)ethenyl]benzoato}-zinc(II) and -copper(II) with 7-fold diamondoid network structures, which are capable of generating SHG, and TPPL depending on an excitation wavelength in the range from 680 nm to 1400 nm. The second order optical nonlinearity, |deff|, of the single crystals has been determined to be 20.05 pm/V (zinc(II) at 900 nm) and 114pm/V (copper(II) at 1000 nm). The two photon absorption cross-section, σ2, is measured to be ~17.86 GM at 680nm for zinc(II). 1. Liu M, Quah H S, Wen S, et al. J. Mater. Chem., 2017, 5(11): 2936-2941. 2. Quah H S, Chen W, Schreyer M K, et al. Nat. Commun., 2015, 6: 7954.

Authors : A.A. Prokhorov1, L.F. Chernush2, R. Minikayev3, J. Lančok1, A.D. Prokhorov2
Affiliations : 1 Institute of Physics AS CR, Na Slovance 2, 18221 Prague, Czech Republic 2 A.A. Galkin Donetsk Institute for Physics and Engineering, R. Luxembourg 72, 83114 Donetsk 3 Institute of Physics, P.A.S., al. Lotnikow 32/46, 02-668, Warsaw, Poland

Resume : Trigonal rare-earth borates RM3(BO3)4 (where R = Y, Eu, La-Lu; M = Al, Ga, Fe, Cr) belong to a new class of multiferroics, in which magnetic, electrical, and order parameters coexist. Rare-earth aluminum borates and gallium borates combine good luminescent and pronounced nonlinear optical properties. They belong to the new generation of materials for lasers. Magnetic properties of the YGa3(BO3)4: x% Cr samples (where x = 0.1, 0.2) were studied using electron paramagnetic resonance (EPR) and X-ray diffraction analysis. Received a new data about the state of doping ions of Cr3 in a single crystal of YGa3(BO3)4 have been obtained when studying the spectra of electron paramagnetic resonance. It is demonstrated that the ions of Cr3 substitute for the trivalent gallium ions. The spectra of three magnetically equivalent ions rotated through 120 degrees are registered. The obtained parameters of spin Hamiltonian of the Cr3 ions in the YGa3(BO3)4 single crystal have been analyzed. The absorption lines associated with the transitions between the levels characterized by unlike quantum numbers differ in width. At the frequency of 9,3 GHz (X band), the width of transition ( -1/2) is 83 Gs, the width of the interdoublet transition is 270 Gs. At the frequency of 33.458 GHz (Q band), the width of transition( -1/2) is 100 Gs, the width of the interdoublet transition is 360 Gs. The width of an absorption line is determined by a number of factors: spin-spin interaction between the chromium ions, electron-nuclear interaction of the Cr3 ions with the nuclear moments of the neighbors, inhomogeneity of the crystal field. Spin-spin interaction between the chromium ions is insignificant because of small concentration of the doping ions. Additionally, the crystallographic structures of the Cr-doped YGa3(BO3)4 in ambient conditions and structure temperature stability in high temperature range were established by in-situ X-ray diffraction. High-temperature XRD measurements demonstrate structure stability of Cr-doped borates in the high temperature range from 300 to 1073 K. Also we have found the unit cell thermal expansion anisotropy for Ga-based borates is 1.26 times higher than for Al-based one.

Authors : Arne Behrent, Antje J. Baeumner
Affiliations : Institute of Analytical Chemistry, Chemo- and Biosensors, University of Regensburg, Germany

Resume : Laser-induced graphene (LIG) is a porous graphene-like material created on commercial polyimide foil with a strong IR laser. By varying the parameters - i.e. laser duty cycle, scanning speed and laser pulse density – one obtains LIG of different morphologies and likely different electrochemical properties. LIG has proven interesting as electrode material for bioanalysis. However, to make reliable electrochemical sensors, a thorough understanding of electrochemical properties as a result of varying LIG process parameters is direly needed. Electrical sheet resistance and peak-to-peak separation in CVs were hence studied and parameters varied systematically on a 30 W CO2 laser system. As the duty cycle is proportional and the scanning speed inversely proportional to the resulting energy density (fluence), it was found that low duty cycles at high speed have no effect while high duty cycles at low speed result in disintegration. However, a broad array of workable settings in between result in highly reproducible and durable electrodes. Furthermore, low pulse density of 500 PPI (pulses per inch) caused anisotropic electrical sheet resistance which changed to isotropic at 2000 PPI. Higher PPI resulted in higher conductivity and lower peak-to-peak separation values with the lowest sheet resistance of approx. 15 Ohm/sq, which is similar to best values reported for screen printed carbon. These electrodes enable fast electron transfer kinetics for a broad range of bioanalytically relevant molecules such as dopamine and acetaminophen. The simple and fast fabrication using low-cost equipment makes these LIG-electrodes a powerful electrode material in point-of-care sensors where otherwise screen-printed electrodes are used.

Authors : Nongnoot Wongkaew,Marcel Simsek, Palaniappan Arumugam, Arne Behrent, Sheela Berchmans, Antje J. Baeumner
Affiliations : Institute of Analytical Chemistry, Chemo- and Biosensors, University of Regensburg, Germany; Council of Scientific and Industrial Research- Central Electrochemical Research Institute, India

Resume : Electrospun polyimide (PI) nanofibers are a potential carbon precursor for generating high performance carbon nanofiber (CNF) electrodes integrated in miniaturized electrochemical sensors where the 3D-structure offers benefits to the system. Using a laser to carbonize electrospun nanofibers is attractive as CNF electrodes can be in situ created with favorable designs and mass production capability. However, unlike lasing PI film their non-uniform and delicate 3D structure can lead to the difficulty in maintaining the nanofibrous features after lasing. In the present work, we aim to unravel crucial factors that facilitate the laser-induced CNFs (LCNFs) with intact morphology and desirable electroanalytical performance. Here, PI nanofibers contained iron and were spun onto an ITO electrode prior to writing the LCNF electrodes by CO2 laser. Control over electrode morphology and electroanalytical performance via electrospinning conditions, iron content, and lasing strategy were thoroughly investigated. Moreover, the effect of these findings on design constraints for electrode fabrication was studied. The as-prepared LCNF electrodes exhibit favorable morphologies and remarkable electron transfer kinetic for both outer- and inner-sphere redox species that are highly comparable to thermal treated CNFs. This work will strengthen the application of 3D-LCNFs in point-of-care diagnostic devices where high sensitivity, short response time, high reproducibility, and low cost are required.

Authors : Bruno Sanches de Lima Valmor Roberto Mastelaro
Affiliations : Sao Carlos Institute of Physics, University of Sao Paulo, 565-905 São Carlos, SP, Brazil

Resume : Nano-composites materials based on reduced Graphene Oxide (rGO) and metal oxide semiconductors (MOS) have been attracting the attention of the scientific community due to its great variety of physical properties and potential applications as solar cell materials, supercapacitors, photocatalytic materials, and chemical sensors. Different synthesis procedures have been employed in order to produce materials with tunable properties and microstructural homogeneity. Within this context, several laser-based methods have been pointed out as a greener and more efficient manner to reduce graphene oxide. Here, we report the reduction of a graphene oxide solution when a nanosecond Nd:YAG pulsed laser is directly focused in the solution under agitation. The rGO solution was then deposited in a substrate with Pt interdigitated electrodes and ZnO nanoparticles were deposited over the rGO layer via RF magnetron sputtering. Our results demonstrate a greener and cheaper path to produce thin films of this nanocomposite based on rGO and ZnO. Also, the gas-sensing performance of this nanocomposite was evaluated regarding ozone detection.

Authors : Bi-Hsuan Lin
Affiliations : National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan

Resume : We have developed successfully the synchrotron based time-resolved X-ray excited optical luminescence (TR-XEOL) and X-ray excited optical luminescence (XEOL) at the TPS 23A X-ray Nanoprobe (XNP) beamline at Taiwan Photon Source (TPS). Not only the TR-XEOL and XEOL, the multifunctional XNP with hard X-ray energy range (4-15 keV) but also includes other featured methods, such as X-ray absorption spectroscopy (XAS), X-ray fluorescence (XRF), cathodoluminescence (CL), X-ray diffraction (XRD) and Bragg ptychography. Based the temporal and high spatial resolution, so that the XNP in a single probe can simultaneously obtain the compositional, optical and structural information. Advanced by energy-tunable hard X-rays, the XNP at TPS provides 40nm spatially resolving means for investigating the optical properties of specific elements in the novel luminescent materials, such as 2D materials, trihalide perovskite and wide bandgap semiconductors. An ultrafast streak camera is synchronized with the pulse structure of the synchrotron ring to investigate the dynamics of luminescence of the materials with temporal resolution 30 ps ~ 1.72 μs in the single bunch mode. In parallel to the construction of the XNP endstation, demonstrative XEOL experiments were studied by unfocused X-ray beam at Taiwan Light Source (TLS). Temperature dependent XEOL and polarization-dependent XEOL were used to study the peculiar near-band-edge (NBE) emission of c-plane and a-plane ZnO wafers, respectively. The detail design of the TR-XEOL and XEOL at XNP, and the demonstrative experimental results of trihalide perovskite CH3NH3PbBr3, 2D materials and a single ZnO microrod will be reported.

Authors : Anita Visan1, Natalia Mihailescu1, Anton Ficai2, Mihai Adrian Sopronyi1, Gianina Popescu Pelin1, Nicolae-Cristian, Mihailescu1, Mihaela Bojan1, José M.F. Ferreira3 and Ion N. Mihailescu1
Affiliations : 1National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, Magurele, Ilfov, RO-77125, Romania; 2Politehnica University of Bucharest, Faculty of Applied Chemistry and Material Science; 1-7 Polizu Str., 011061 Bucharest, Romania; 3Department of Ceramics and Glass Engineering, University of Aveiro, CICECO, 3810-193 Aveiro, Portugal;

Resume : Magnesium/Magnesium alloys layers stand for a hot topic in recent research devoted to the development of biodegradable metallic implants which are safely dissolved, in time, with a controlled rate. This is due to an accumulation of positive circumstance such as: degradability, excellent biocompatibility, low density and relatively low costs. Once in the body, Mg is progressively resorbed, and no secondary surgery is required to remove implant remains after healing. Mg/Mg alloys are prone to rapid corrosion in physiological environment resulting in the synthesis of magnesium oxide/hydroxide layers and release of hydrogen gas. Bioactive glasses are recognized as “intelligent” materials, which convert inside human body to hydroxyl-carbonated apatite layers, very similar to the inorganic part of the bone. We report herewith on deposition of Bioactive Glass films by PLD onto biodegradable metallic (Mg/Mg alloy) substrates. The deposition was conducted with a KrF* excimer laser source. The coatings well reproduce the initial composition in targets, as demonstrated by complementary physical-chemical analyses via: IR spectroscopy, SEM, EDS and XPS. In vitro tests after immersion in physiological fluids were conducted to evaluate the corrosion resistance of uncovered vs covered biodegradable metallic implants. The results support the idea of fabrication of efficient shield barriers against corrosion on Mg/Mg alloys for use in a new generation of biodegradable metallic implants.

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Novel laser patterning and processing applications : Thomas Lippert
Authors : A. Cubero 1, E. Martínez 1, L.A. Angurel 1, G.F. de la Fuente 1, R. Navarro 1, H. Legall 2, J. Krüger 2, J. Bonse 2.
Affiliations : 1 - ICMA (Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza), Zaragoza, Spain; 2 - BAM (Bundesanstalt für Materialforschung und –prüfung), Berlin, Germany.

Resume : It is well known that the use of ultrashort (fs) pulsed lasers can induce the generation of (quasi-) periodic nanostructures (LIPSS, ripples) on the surface of metallic samples[1]. Such nanostructures have also been observed in sample’s surfaces that have been irradiated with UV lasers with a pulse duration of 300 ps. In this work, we compare the characteristics of these nanostructures on 25-micrometer thick Nb sheets induced by different pulsed lasers, and we analyze the influence of the different parameter conditions that were selected for the laser processing. In addition to conventional continuous or burst mode processing configurations, a meandering laser line scanning has also been investigated. This configuration allows the processing of large areas with a more uniform distribution of nanostructures at the surface. The influence of these nanostructures on the superconducting properties of Nb has also been investigated. With this aim, magnetic hysteresis loops have been measured at different temperatures to analyze how these laser treatments can affect the flux pinning behavior and, in consequence, their critical current values. This research is partially supported by projects ENE2017-83669-C4-1-R (Agencia Estatal de Investigación & Programa FEDER), Gobierno de Aragón (Research group T54_17R). References [1] J. Bonse, S. Höhm, S. V. Kirner, A. Rosenfeld, and J. Krüger, “Laser-induced periodic surface structures – a scientific evergreen,” IEEE J. Sel. Top. Quantum Electron., vol. 23, no. 3, p. 9000615, 2017.

Authors : Rajath Sawant, Purva Bhumkar, Alexander Y. Zhu, Peinan Ni, Federico Capasso, Patrice Genevet
Affiliations : [Rajath Sawant; Purva Bhumkar;Peinan Ni;Patrice Genevet - CNRS CRHEA, Université Côte d’Azur, rue Bernard Gregory, Sophia Antipolis 06560, Valbonne, France] [Alexander Y. Zhu; Federico Capasso - John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA]

Resume : Conventional optical components like lenses undergo dispersion leading to chromatic aberrations resulting in poor imaging. The most popular technique in practice to correct it is to use series of cascading lenses, which results in bulky devices. Metasurfaces, an array of nanoantennas of sub-wavelength thickness can be employed to achieve this as they are compact and effective. Through our work, we demonstrate dispersion compensation using metasurface in a simpler case of a prism and show the design of a dispersion compensator metasurface for a plano-convex lens with ray tracing results. Metasurfaces are known to cause abrupt phase and polarization shift in the outgoing light. For a desired functionality, one can fabricate the metasurface with corresponding phase profile using nanoantennas. For our study, we use constant phase gradient metasurface made of TiO2 nanopillars (dielectric material) on SiO2 substrate. This can be obtained by placing 0 to 2π phase elements in the increasing order along one particular direction and periodically repeating the same arrangement. One can see that this mimics the conventional blazed gratings in design and also functionality. All in all, the motivation of this work is to combine refractive and diffractive components to mitigate dispersion as both have opposite sense of dispersion. The generalized laws of refraction at the metasurface-air interface are used for the calculations. The phase gradient is a parameter to design the metasurface given the angle of transmission, incidence and the wavelength of incident light. The technique of Fourier plane imaging and spectroscopy is utilized to study minute angles of dispersion in the prism’s case. The results obtained are for broadband visible region of 550-700 nm.

Authors : C. Kapnopoulos1, E. Mekeridis2, A. Zachariadis1, P. Prodromidis1, A. Laskarakis1, C. Gravalidis1, S. Logothetidis1
Affiliations : 1 Lab for Thin Films - Nanobiomaterials - Nanosystems & Nanometrology (LTFN), Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece 2 Organic Electronic Technologies (OET), Antoni Tritsi 21B, 57001 Thessaloniki, Greece

Resume : Ultra-fast laser processes are among the key technologies for the manufacturing of flexible organic electronic devices. These are alternative techniques to photolithographic methods and they have the advantage for im-plementation to roll-to-roll (R2R) manufacturing processes for the low-cost and large area production of numer-ous flexible Organic Electronic devices, such as Organic Photovoltaics (OPVs). The optimization of the laser pro-cess parameters for the selective removal of the different nanomaterials for OPVs (transparent electrodes, pho-toactive blends, buffer layers, cathode electrode) with high precision and without affecting the underlying nanolayers is of paramount importance. In this work, we present a robust process for the precise laser patterning (P1, P2 and P3) of OPV nanolayers in inverted device structure onto flexible polymer substrates using ps laser system. These include state-of-the-art inorganic nanomaterials (e.g. Indium Tin Oxide, Ag Nws, IMI, AZO, WOx), as well as transparent polymers (e.g. PEDOT:PSS) and photoactive polymers as electron donors (e.g. polythiophenes) and acceptors (e.g. fullerene derivatives, PCBM, etc.) or state of the art ready to use photoactive inks (e.g. PI-5, OETD1A1) in single and multilayer structures. Also, we investigate the effect of the laser process parameters (e.g. fluence, speed) on the patterning shape and quality, in order to obtain high quality patterned shapes with minimum amount of debris and sharp interfaces. Finally, we present the implementation of the ultra-fast laser patterning process in the manufacturing of OPV modules and we demonstrate the potentiality of low cost ultra-fast laser processes to be used as a standard pro-cess step for r2r manufacturing processes for Organic and Printed Electronics devices.

Authors : Lin Chai
Affiliations : Dr Artem Bakulin (AB);Dr Aleksandar Ivanov (AI);Prof Joshua B. Edel (JBE)

Resume : Single-molecule electrochemical sensors are currently used in DNA and protein sequencing and for analysis of protein-protein interaction. Nanopore-based sensors would potentially benefit from higher spatial and temporal resolution when achieving more accurate sequencing. We will report the initial results of the project that aims to combine tunnelling nanojunctions based on device reported by Nadappuram1 with ultrafast spectroscopy approaches. Ultrafast spectroscopy developed to reveal electronic dynamic at a picosecond level can potentially increase the time resolution of electrochemical sensors. A sequence of ultrafast optical pulses will illuminate the devices. First, ‘pump’ pulse can bring molecular to excited states, and then ‘push’ pulse can modify the excited state in an extremely short time and give rise to changes of tunnelling current. We believe the combination of ultrafast spectroscopy with nanoscale tunnelling current detection will lead to a new single-molecule characterisation method with high spatial and temporal resolution. 1 B. P. Nadappuram, P. Cadinu, A. Barik, A. J. Ainscough, M. J. Devine, M. Kang, J. Gonzalez-Garcia, J. T. Kittler, K. R. Willison, R. Vilar, P. Actis, B. Wojciak-Stothard, S.-H. Oh, A. P. Ivanov and J. B. Edel, Nat. Nanotechnol., , DOI:10.1038/s41565-018-0315-8.

Authors : Jen Manerova, Dominika Gastol, Chris Smith, Matthew Capener, Anna Alvarez-Reguera, Emma Kendrick, Vannessa Goodship, James Shaw-Stewart, Ben Millsom
Affiliations : University of Warwick, M-Solv Ltd, and University of Birmingham

Resume : The use of Li-ion batteries (LIBs) in electric vehicles (EVs) is increasing the need to improve and optimise LIB manufacture and recycling. Recycling can involve complete material breakdown into constituent elements, often termed urban mining, or reclamation of individual components. In LIBs the most valuable components are the electrodes, and so retaining the high value of these components is a priority in end-of-life processing. This work focusses on laser cleaning of LIB electrodes, particularly targeting a concept known as the ?solid-electrolyte interface? (SEI) where resistive materials build up on the surface of the electrode, increasing the impedance of charge-transfer within the cell. For the negative electrode the most conventional chemistry of graphite on copper foils has been used, and the positive electrode aluminium coated in Li-metal oxide (where the metal is a mixture of Ni, Mn & Co). The original surface processing has involved cleaning of the top of used electrodes to revitalise the electrodes before re-inserting them into coin cells to test the electrochemical properties. The used electrodes are usually double-sided, and so laser cleaning was also used to completely remove the electrode from the reverse side in preparation for single-sided coin-cell fabrication. A 70W 1064nm, ns-pulsed fibre laser has been used with a rep rate of up to 1 MHz. The parameters have been tuned to optimise the removal of material from the electrodes, with the corresponding electrochemical results presented clearly. This work explores the effect of laser cleaning of the surface of used LIB electrodes, a process that could reclaim more value from used LIBs than conventional urban mining.

09:45 Coffee break    
Authors : D. Kuczy?ska-Zem?a (1), E. Kije?ska-Gawro?ska (1), M. Pisarek (2), P. Kwa?niak (1), P. Borowicz (2), H. Garbacz (1)
Affiliations : (1) Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw, Poland; (2) Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland

Resume : A promising method for producing surface patterns in the micro- and sub-microscale is direct laser interference lithography (DLIL). In this technique two or more laser beams interfere each other and generate a periodic pattern on the surface. Especially important feature, when it comes to functionalization of implantable elements with original roughness, such as passive middle ear implants, is possibility of local modification of the surface after two commonly used surface treatments ? shot peening and acid etching. Therefore, in this study DLIL was used to produce periodic grooved and island pattern on titanium surfaces after shot peening and acid etching. In this study Nd:YAG laser operating 1064 nm wavelength, with the pulse duration 10 ns, energy density 400 mJ cm-2 and 7 laser pulses was applied. In order to characterized biological response the bioactivity and cell adhesion tests were performed. The bioactivity of the surface was investigated using SBF immersion tests, in different soaking times (0.5 h to 168 h). The deposited apatite layers on titanium surface were deeply evaluated using SEM, XPS, EDS and FTIR. For the cell (MG 63) adhesion tests similar short incubation times were applied. The adhered cells were analyzed using confocal microscopy and SEM observations. The obtained results of biological response were analyzed by correlating with the results of the physicochemical properties of the modified titanium surfaces. Our results showed that DLIL modified surfaces exhibit better biological activity compared to shot peened and acid etched one. Presented methodology can be used as an effective tool for manufacturing controlled surface structures improving the bone?implants interactions. This research was financially supported by The National Science Centre Poland under Grant no. 2016/23/N/ST8/02044.

Authors : Andrei Popescu1, Marc Leparoux2
Affiliations : 1. Center for Advanced Laser Technologies - CETAL, National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania 2. Laboratory for Advanced Materials Processing, EMPA, Feuerwerkerstrasse 39, 3602 Thun, Switzerland

Resume : Metal matrix nanocomposites are materials with enhanced mechanical resistance, tensile strength, wear resistance or thermal conductivity as compared to bare metals or alloys, with the added benefit of reduced weight. They could be the materials of the future and replace at large scale the metallic alloys of today in automotive, military or aeronautic fields. However, these are materials that allow for limited machining. In case of laser processing of nanocomposites, there are difficulties caused by melting that can induce dispersed phase segregation and thus possible mechanical properties downgrade. Moreover intense ablation during laser irradiation and generation of intense spatter are also severe drawbacks in machining. We tried to overcome this last aspect by tuning the laser parameters under high speed monitoring during processing of an aluminium alloy reinforced with alumina nanoparticles. Imaging via an optical microscope allowed for recording at millimeter level, providing new information on liquid-metal dynamics during laser irradiation as well as plausible explanations for spatter occurrence and pores formation. Droplets trajectory and speed were assessed by computerized image analysis. It was found that the velocity of visible droplets expulsed laterally or at the end of the plume emission from the metal surface was not dependent on the plasma plume speed. It was observed that the number of droplets on surface was 1.5–3 times higher when the laser beam was focused in depth as compared to focused beams, even though the populations average diameter were comparable. Three methods were tested for removing droplets in situ, during plume expansion: an argon gas jet crossing the plasma plume, a fused silica plate collector transparent to the laser wavelength placed parallel to the irradiated surface and a mask placed onto the aluminium composite surface.

Authors : Maxim Neradovskiy, Aurélie Jullien, Umberto Bortolozzo, Stefania Residori, Adriana Scarangella, Michel Mitov
Affiliations : Institut de Physique de Nice, Université de Nice Sophia-Antipolis, CNRS UMR 7010, 1361 route des Lucioles, 06560 Valbonne, France; Institut de Physique de Nice, Université de Nice Sophia-Antipolis, CNRS UMR 7010, 1361 route des Lucioles, 06560 Valbonne, France; Institut de Physique de Nice, Université de Nice Sophia-Antipolis, CNRS UMR 7010, 1361 route des Lucioles, 06560 Valbonne, France; Institut de Physique de Nice, Université de Nice Sophia-Antipolis, CNRS UMR 7010, 1361 route des Lucioles, 06560 Valbonne, France; Centre d’Elaboration de Matériaux et d’Etudes Structurales, CNRS UPR 8011, University Paul-Sabatier, 31055 Toulouse, France; Centre d’Elaboration de Matériaux et d’Etudes Structurales, CNRS UPR 8011, University Paul-Sabatier, 31055 Toulouse, France

Resume : Cholesteric liquid crystal (CLC) phase exhibits a helical structure with a twist axis perpendicular to the local molecular director. When light propagates in the Bragg regime through a CLC slab with a planar texture, the medium gives rise to Bragg reflection. As shown previously, CLCs are involved in ultrafast optical applications (e.g., slow light and temporal laser pulse shaping). In particular, they can be used to compress laser pulses due to their 1-D photonic nature, and a combination of high birefringence and nonlinearity. Here we propose to use a femtosecond source and an advanced statistical experimental approach for detailed characterization of the ultrafast temporal changes undergone when a pulse propagates through the bandgap edges of CLC. Home-made CLC samples with a thickness ranging from 14 to 56 µm present a variable spectral bandgap so that the laser spectrum overlaps partly with the blue or red edge Fourier-transform spectral interferometry analysis then enables to recover the changes of spectral intensity and phase of pulses transmitted through. Furthermore, a cluster analysis technic of collected from 1000 to 2000 data points allowed us to estimate the microscopic homogeneity of the samples. As a result, we estimate the temporal changes undergone by the laser pulse, depending on the relative position of the laser spectrum and bandgap edges.

Authors : K. Huet 1, J. Aubin 1, B. Curvers 1, A. Verstraete 1, B. Lespinasse 1, F. Mazzamuto 1, A. Sciuto 2, S.F. Lombardo 2, A. La Magna 2, P. Acosta-Alba 3, L. Dagault 3, S. Kerdiles 3
Affiliations : 1 Laser Systems and Solutions of Europe, SCREEN Semiconductor Solutions, Co., Ltd., 14-30 rue Alexandre, 922230 Gennevilliers, FRANCE;2 CNR-IMM, VIII Strada 5, 95121 Catania, ITALY;3 Univ. Grenoble Alpes, CEA, LETI, 38000 Grenoble, France

Resume : Pulsed laser annealing is one of the promising low thermal budget approaches to overcome process limitations and develop alternative schemes to achieve better device performance and enable 3D architectures. Its applications range from the Front End Of Line (doping, contacts, strain engineering) to Back End Of Line (Cu grain engineering) in logic and memory. One key enabler for integrating this disruptive technology in the coming highly challenging technology nodes is an accurate time-resolved modeling of laser matter interaction, thermal diffusion, phase change and species diffusion at the nanosecond timescale, all to be solved self-consistently. In this paper, we will present the 3D TCAD simulation package of the Laser Annealing process (Laser Annealing Innovation Application Booster or LIAB), with a specific focus on the enthalpy and phase field models and calibration of relevant materials. The coupled partial differential equation system is described and a methodology for materials calibration, especially challenging in the melting regime, is detailed with results shown for group-IV and Back End Of Line materials.


Symposium organizers
Mihaela FILIPESCUNational Institute for Lasers, Plasma and Radiation Physics

409 Atomistilor Street, Magurele, 077125, Romania

+40 214 574 414
Stephan BARCIKOWSKIUniversity of Duisburg-Essen

Technical Chemistry I - Universitaetsstraße 7, 45141 Essen, Germany

+49 201 183 3150
Tatiana ITINAUMR CNRS 5516 / UJM / University of Lyon

Laboratoire Hubert Curien, Campus Manufacture, 18 rue du Pr. B. Lauras, 42000 Saint-Etienne, France

+33 477915829
Thomas LIPPERTPaul Scherrer Institut

OFLB U110, CH-5232 Villigen PSI, Switzerland

+41 56 310 4076