2018 Spring Meeting
MATERIAL PROCESSING AND CHARACTERIZATIONX
Photon-assisted synthesis and processing of materials in nano-microscale
After more than fifty years since its “birth”, the laser is a modern, efficient and elegant tool, with applications in physics, chemistry, biology, analytics, material science, medicine, space and security. The proposed symposium provides an interdisciplinary forum to discuss recent progress in the area of laser-matter interaction and photon processing of materials for basic and applied research.
The main pillars of laser-matter interaction, synthesis, processing and diagnostics will be covered from the nanosecond to the femtosecond time scale, pointing at the fabrication and characterization of nanostructures, thin films, heterostructures, for fundamental and applied research. The symposium will have a cross-discipline framework based on physics, chemistry, and the various theoretical modeling aspects of photon-matter interactions.
Current and futuristic applications in materials engineering from nano to microscopic scale will be discussed, including application in optoelectronics, biomaterials, sensors, nanocatalysis and electronics, synthesis of non-conventional materials with Free Electron Laser, medicine and non-contact art restoration. In addition to laser light, the interaction of high-energy photons for photochemical processing is also among the scientific topics of the symposium. The photo-induced chemical reactions and material modifications are of wide interest for the processing of organic, inorganic and biological surfaces, as well as for a number of industrial applications.
Hot topics are methods that overcome the optical diffraction limit, 3D nano and micro fabrication (including fabrications buried inside a material), growth of innovative nanostructures for applications ranging from photonics to bio-engineering, ultrashort high intensity lasers and applications, eco-design through processing of photovoltaic cells, thermoelectric materials and devices, micro and nanosystems for energy storage and conversion.
This symposium will focus on the inherent interdisciplinarity of laser and photon materials processing thus offering to all participants of the E-MRS conference a multidisciplinary forum covering a wide range of fundamental and applied applications.
Bringing together young scientists with experts in the field of photon materials processing will promote the discussion of exciting ideas as well as the transfer of knowledge to the next generation of scientists.
Hot topics to be covered by the symposium:
- Laser nanostructuring and nanoparticle generation
- Laser processing of soft matter (polymers, biomaterials): LIFT, MAPLE
- Pulsed laser deposition of thin films: interface phenomena
- Ultrashort high intensity laser pulse; interaction with materials
- Laser-based spectroscopy and plasma diagnostics
- Ripple formation in fs laser ablation of metals and ceramics
- Ultrafast probing techniques and results
- Laser ablation in art restoration/conservation
- FEL direct synthesis of functional materials
- Nanophotonics and Biophotonics
- 3D processing of material and applications
- Industrial applications of Laser Patterning
- Multiphoton processing by chemical reactions: multiphoton polymerization, reduction or modification with ultrashort laser pulses
Tentative list of invited speakers:
- Patrick Hoffmann, EMPA, Switzerland
- James Lunney, Trinity College Dublin, Ireland
- Maria Farsari, FORTH IESL, Greece
- Ionela Vrejoiu, University of Cologne, Germany
- Chantal Leborgne, GREMI Orleans, France
- David Geohegan, Oak Ridge National Lab, USA
Selected articles will be published in Applied Surface Science (Elsevier).
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Pulsed laser ablation I : Maria Dinescu
Authors : M. A. Sahiner_1, W. Cockerell_1, J. Steier_1, R. Vander Valk_1, S. Kelty_1, R. Morea_2, J. Gonzalo_2, J. Woicik_3
Affiliations : 1 Seton Hall University, South Orange New Jersey, United States ; 2 CSIC, Madrid, Spain ; 3 NIST, Gaithersburg Maryland, United States
Resume : The crystal structure of Niobium-lead-germanate, Nb₂O₅-PbO-GeO₂ (NPG), glass thin films on silicon substrates were investigated by using EXAFS and Density functional theory (DFT) based simulated standards. NPG glasses are promising candidates for applications in nonlinear optical devices because they exhibit high nonlinear third order optical susceptibility. In this work NPG glasses were prepared with pulsed laser deposition (PLD) method with varying oxygen partial pressure to induce thin films with different oxygen stoichiometry. In our study of these materials we have discovered interesting crystal structure responses to partial oxygen deposition pressure¹. In this study, we have prepared a series of Nb₂O₅-PbO-GeO₂ glasses on Si substrates under various oxygen partial pressures from vacuum to 5Pa. Glancing incidence EXAFS and measurements were performed at Brookhaven National Laboratory. Then we have used DFT based calculated references and experimental references to identify the crystal phases present in the thin films prepared with various partial oxygen pressures. The results of the EXAFS non-linear square fits will be discussed to correlate the PLD deposition parameters to the final phases obtained in these thin films. 1. Sahiner et al., Journal of Physics 712, 012103 (2016).
Authors : Daniel Schumacher; Wolfgang Stein
Affiliations : SURFACE systems+technology GmbH+Co KG, Hueckelhoven, Germany
Resume : TwinBeam PLD - new possibilities for advanced functional films Daniel Schumacher, Wolfgang Stein SURFACE systems+technology GmbH+Co KG, Hueckelhoven, Germany At present the growth of thin films by using the PLD technique is limited to the availability of dense ceramic targets of the stoichiometric compounds. Some phases do not withstand the sintering conditions and therefore poorly sintered or composite targets are used instead. This may bring some problems of particle ejection and composition deviations in the growing film. Another typical problem in PLD arises when some element in the compound has a higher volatility (Pb, Bi, etc), which induces serious deviations in the film composition. This is normally compensated by preparing targets enriched in the volatile element, which needs to be adjusted for each deposition conditions. These limitations can be overcome by the use of simultaneous ablation of two targets to composit the final film material. The new SURFACE Twin Beam PLD technology makes use of a dual laser beam of the same laser, separated by a laser beam splitter and a new target manipulator that combines three standard single targets (2"diameter) ablation with a Twin Beam target pair (2 x 1"diameter) position for the simultaneous ablation. The angle of the twin targets can be adjusted from a confocal to a cross beam configuration. This new technology does not need a new PLD system, it is an available upgrade for all SURFACE PLD-Workstation systems. The new TwinBeam option includes only an upgrade of the standard target manipulator to the TwinBeam version. The necessary additional beam line is an extension to the existing one and the tuning of the fluence will be done with two manual or motorized laser beam attenuators. A software upgrade incorporates this new feature in the highly flexible PLUMEmaster user interface. New process features are integrated and fully software controlled: - software controlled in-situ fluence variation between the two targets - fluence modulation of one beam synchron to the RHEED oscillation of the film growth - synchronic variation of the plume angle at TwinBeam targets from a cross-beam1) to confocal plume to parallel plume orientation - enhanced combinatorial features: + in-situ composition spread deposition (ICSD) of two materials + better material mix with no limitation of film thickness and no post-annealing step + large fluence differences and modulation possible to combine metals with oxides The TwinBeam option extends the flexibility of the SURFACE PLD workstation and is a powerful support of the SURFACE wedge heater which allows other combinatorial operations like wedge shaped films or deposition through shadow masks. References: Tselev, A., Gorbunov, A. & Pompe, Cross-beam pulsed laser deposition of ultrathin multilayer metal films, W. Appl Phys A (1999) 69: 353 W.Stein, D.Schumacher, Universal Wedge Generator for Oxide Film Deposition in Laser MBE Systems, poster WOE23 , Nanjing 2016
Authors : Mónica Fernández (1), Jesús del Val (1,3), Mohamed Boutinguiza (1), Antonio Riveiro (1), Rafael Comesaña (2), Fernando Lusquiños (1), Juan Pou (1,3)
Affiliations : (1) Applied Physics Department, University of Vigo, Lagoas-Marcosende, E-36310, Vigo Spain. (2) Materials Eng., Applied Mech., and Construction Dpt., University of Vigo, Lagoas-Marcosende, E-36310, Vigo, Spain. (3) Department of Mechanical Engineering, Columbia University, New York, New York 10027, USA
Resume : The unique physical and chemical properties related to the size effect when compared to bulk material, such as good conductivity, antibacterial or antifungal effects, catalytic activity, etc. make silver nanoparticles very useful in many different areas. Although not only the size is behind these particular properties also shape of the particles which depends on the fabrication method. In this work silver nanoparticles were produced by using two nanosecond Nd:YVO4 lasers operating at 1064 and 532nm respectively to ablate a silver target submerged in pure de-ionized water. Part of the resulting colloidal solution was re-irradiated one and three times with the same laser, using an air pressure system designed to resize and get uniform nanoparticles. The obtained nanoparticles were characterized by means of transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS) and UV/VIS absorption spectroscopy. The as-ablated nanoparticles present diameters of a few nanometers, rounded shape with certain tendency to agglomeration. The size of the nanoparticles was reduced by subsequent laser re-irradiation. The number of nanoparticles with a diameter lower than 10nm increased with the re-irradiation time. Part of the re-irradiated particles coalesce forming chains-like nanostructures. All nanoparticles (as-ablated and re-irradiated) are crystalline.
Authors : S.A. Irimiciuc1, S. Gurlui1, P. Nica2, M. Agop2, C. Focsa3
Affiliations : 1Faculty of Physics, Atmosphere Optics, Spectroscopy and Lasers Laboratory “Alexandru Ioan Cuza” University of Iasi, 700506 Iasi, Romania 2Department of Physics, “Gh. Asachi” Technical University, 700050 Iasi, Romania 3Univ. Lille, CNRS, UMR 8523 - PhLAM - Physique des Lasers, Atomes et Molécules, F-59000 Lille, France
Resume : Dynamics of transient plasmas generated by laser ablation in nanosecond, picosecond and femtosecond regimes were investigated by means of electrical and space-and time-resolved optical emission spectroscopy diagnosis techniques. The aim of this work was to experimentally investigate the dynamics of transient plasmas generated by laser ablation in various regimes, and attempt to correlate the observed behavior with the physical properties of the ablated materials (atomic mass, electrical and thermal conductivities, melting, boiling points etc.). The experiments were performed in similar conditions of laser fluence (8.7-10 J/cm2) background pressure (p = 10-5 - 10-6 Torr) and probe-target axial distances (d = 1 - 40 mm) for all the investigated plasmas. Time-resolved optical investigations were focused on recording images of the laser-produced plasmas at different time delays with respect to the ablation laser pulse, in order to investigate the structure of the plasma plumes and their global dynamics. The electrical investigations were performed by means of Langmuir probe method, which consists of immersing a metallic probe in the plasma volume, biasing the probe (-/+ 30V) and extracting the electronic or ionic currents. This led to the possibility of building space-time maps of the main plasma parameters (electron temperature, plasma potential, thermal velocity, ionic density, etc.). The data resulted from these fundamental investigations are discussed with respect to the particularities to each ablation regimes. We also report here for the first time empirical relations connecting the plasma parameters with the physical properties (electrical/thermal conductivity, atomic mass, heat of vaporization) of the target. The empirical laws proposed here are respected in all three ablation regimes (ns, ps, fs).
Pulsed laser ablation II : Cristian Focsa
Authors : Ionela Lindfors-Vrejoiu
Affiliations : II. Physics Institute, University of Cologne, Germany
Resume : Pulsed-laser deposition (PLD) is a powerful film growth technique, applied with great success in the case of complex oxide epitaxial mutilayers. Here I focus on the PLD growth of heterostructures and superlattices in which topological magnetic structures can be stabilized. In superlattices interactions at coherent interfaces may result in spectacular physical effects. For instance, at the interface between a ferromagnetic oxide layer and a heavy 5d metal oxide it is expected that interfacial Dzyaloshinskii-Moriya interaction may competitively act to destabilize collinear magnetic order and generate chiral magnetic order, in certain temperature and magnetic field ranges. We studied the Hall effect in epitaxial layers of ferromagnetic SrRuO3 interfaced with non-magnetic insulating 4d and 5d transition metal oxides. Hall resistivity measurements of the superlattices showed that besides the contributions from the ordinary and anomalous Hall effect, expected for ferromagnetic thin films, an additional contribution occurred, which resembled a topological Hall effect. This additional anomaly of the Hall resistivity indicated that non-trivial topological magnetic textures might form in the SrRuO3 layers of the superlattices. This finding holds promise for the generation of skyrmions in all-oxide epitaxial superlattices that are suitable for electric field effect experiments.
Authors : Robert W Eason, James A Grant-Jacob, Jake J Prentice, Sergey V Kurilchik, Jacob I Mackenzie.
Affiliations : Optoelectronics Research Centre, University of Southampton, Highfield, Southampton, SO171BJ, UK
Resume : The quality of pulsed laser deposited (PLD) films can suffer from the undesirable incorporation of particulates within the growing film that can originate from the build-up of cones and other surface features on the target surface during ablation. After repetitive exposure to the incident laser pulses, tips of these cones can detach and become embedded in the film, leading to micron-scale defects which are problematic for the growth of high quality single crystalline optical waveguides. The cones formed on the target surface point towards the incident laser direction, and hence a PLD set-up is needed where there is no unique direction of incidence on the target, which should theoretically reduce or ideally eliminate any cone build-up and subsequent problems of particulate generation. We are currently implementing a target geometry where regions are ablated sequentially from equal and opposite angles about the target normal via a bespoke rotation and translation protocol intended to prevent cone formation. Our premise is that such a symmetry-breaking irradiation format away from a purely rotational motion of the target has no preferred overall direction, hence there can be no preferential direction for cone growth. We will present our results that quantify the reduction of particulates within PLD-grown films, using this novel procedure which is intended to further improve the quality, in terms of reduced optical loss, of our ~ 10 µm-thick optical waveguides.
Authors : A. Maffini, D. Dellasega, A. Pazzaglia, V. Russo, M. Zavelani-Rossi, M. Passoni
Affiliations : A. Maffini: Dipartimento di Energia, Politecnico di Milano, Via Ponzio 34/3, 20133 Milano, Italy; D. Dellasega: Dipartimento di Energia, Politecnico di Milano, Via Ponzio 34/3, 20133 Milano, Italy, Istituto di Fisica del Plasma "P. Caldirola" (IFP-CNR) via R. Cozzi 53, 20125 Milano, Italy; A. Pazzaglia: Dipartimento di Energia, Politecnico di Milano, Via Ponzio 34/3, 20133 Milano, Italy; V. Russo: Dipartimento di Energia, Politecnico di Milano, Via Ponzio 34/3, 20133 Milano, Italy; M. Zavelani-Rossi: Dipartimento di Energia, Politecnico di Milano, Via Ponzio 34/3, 20133 Milano, Italy; M. Passoni: Dipartimento di Energia, Politecnico di Milano, Via Ponzio 34/3, 20133 Milano, Italy, Istituto di Fisica del Plasma "P. Caldirola" (IFP-CNR) via R. Cozzi 53, 20125 Milano, Italy;
Resume : Ultra-low density porous materials (1-20 mg/cm3, also known as “foams”) show unique features (e.g. perfect black body behavior and a high surface-to-volume ratio) of great interest for many scientific and technological applications, including cutting-edge research topics as the generation of laser-driven particle beams . Thanks to its versatility in a wide range of process parameters, the Pulsed Laser Deposition (PLD) technique is an ideal tool to obtain ultra-low density coatings with finely tuned properties. In previous works we have shown that it is possible to produce ultra-low density foams by means of PLD with nanosecond laser pulses [2,3]. In this contribution we present the most recent advances in the PLD of carbon foams. We investigate, both theoretically and experimentally, the process of foam growth starting from the coalescence of carbon nanoparticles in the peculiar PLD regime characterized by ns pulses and high background pressure (up to 1000 Pa), showing how it is possible to control density profile (down to 10 mg/cm3), mesoscale morphology and thickness (down to 2 microns) while preserving a good spatial uniformity. In addition, we address the possibility of growing low-density nanostructures exploring a novel PLD regime characterized by ultrashort (<100 fs) and high energy (> 5mJ) laser pulses.  I Prencipe et al., High Power Laser Sci. Eng. 5 (2017)  A Zani et al., Carbon 56 358 (2013)  I Prencipe et al., Plasma Phys. Control. Fus. 58 034019 (2016)
Authors : Giorgio Baraldi (1,2), Monica Martinez-Orts (1), Esther Soria (3), Johann Toudert (1), Rosalia Serna (1), Jose Gonzalo (1)
Affiliations : (1) Laser Processing Group, Instituto de Optica, IO, CSIC, Serrano 121, Madrid, Spain; (2) Present Address: CIC Energigune-Parque Tecnológico de Alava, Miñano, Spain; (3) SAFTRA Photonics, Jesenná 5, Košice Slovakia;
Resume : Conformal coatings are essential to develop microelectronic and photonic structures since they not only protect them but they also enable additional functionalities, for example as absorbers. In this work we demonstrate the nanometric conformal growth of a pulsed laser deposited (PLD) thin transparent amorphous Al2O3 (a-Al2O3) cover layer on 2D Ag nanoparticle (NP) arrays that show a strong localized surface plasmon resonance (LSPR) response. The 2D Ag NP array was formed by depositing a percolated Ag film by PLD in vacuum, followed by a thermal annealing in air at 300 ºC to allow the formation of well separated Ag semispheroidal NPs by dewetting (average in-plane diameter 100 nm, maximum height ~70 nm). Finally the a-Al2O3 cover film (~70 nm thick) was deposited on top of them. SEM analysis shows that the cover film induces no relevant alteration of the morphology and organization of the 2D Ag NP arrays. The surface topography of the a-Al2O3 film shows the presence of nanodomes, with sizes determined by those of the underlying Ag NPs, therefore confirming its conformal nature. The presence of the cover film shifts the characteristic dipolar and quadrupolar LSPRs of the Ag NPs to lower energy values (by about 0.5 eV), and increases the overall specular and diffuse reflectance. The possibility of achieving near-Brewster conditions with this structure and its possible application for light-harvesting and optical sensing will be discussed.
Authors : M. Censabella, F. Ruffino, M. G. Grimaldi
Affiliations : Dipartimento di Fisica e Astronomia Università di Catania, via S. Sofia 64, 95123 Catania, Italy MATIS CNR-IMM via S. Sofia 64, 95123 Catania, Italy
Resume : Mono-metallic and bi-metallic Pd and Pt nanoparticles (NPs) find important applications for sensing detection, catalysis, hydrogen storage, etc. However, the success of such technologies is subjected to the development of simple, versatile, low-cost, high-throughput methods for the controlled production of the NPs. In addition, the physico-chemical response of these NPs can be tuned by controlling their size and composition, so that the fabrication methods should allow such a fine control. To meet these requirements, we present a laser-assisted synthesis method for the production and processing of mono- and bi-metallic Pd and Pt NPs. It is based on the nanosecond-pulsed laser ablation, in liquid environment, of pure Pd or Pt targets and of Pd-Pt multilayer deposited films. In particular, using microscopy (SEM, AFM, TEM) and optical (absorbance, Raman, XRD) analysis techniques, we show the effect of the process parameters (total ablation time, laser fluence, liquid environment) on the structural and chemical characteristics of the NPs (size, shape, composition, crystallinity). We establish, therefore, a general working framework for the controlled nanofabrication, in solution, of the Pd, Pt, and PdPt NPs exploiting the laser-metals interaction and we discuss the microscopic physical mechanisms determining the NPs characteristics. Finally, we show, also, the possibility to transfer the NPs on graphene substrates presenting some properties of the resulting nanocomposites.
Pulsed laser ablation III : Ionela Lindfors-Vrejoiu
Authors : Tony MAULOUET(1,2), Michel SALZET(1), Isabelle FOURNIER(1), Michael ZISKIND(2), Cristian FOCSA(2)
Affiliations : (1) Laboratoire PRISM INSERM U1192, Université Lille 1, Villeneuve d’Ascq, France (2) Laboratoire PhLAM-CNRS UMR 8523, Université Lille 1, Villeneuve d’Ascq, France
Resume : Conventional MALDI MS imaging is widely used in proteomics. However, due to the inherent complexity of the biological tissue it has certain limitations in the detection and identification of heavy proteins (>30 kDa). Various strategies have been developed to overcome this issue. All require a micro-sampling step. Different techniques have been specifically applied for this purpose. However, their spatial resolution is typically about 1mm and it is a real challenge to develop a tool with a sufficient yield to reduce the size of the sampled area. We have explored the potential of a new micro-sampling technique based on an indirect substrate-mediated laser ablation (SMLA) mechanism which permits the use of low deposited energy while preserving the biological content. Taking advantage of this effect, analyses of micro-sampled tissue were performed, demonstrating the identification of 400 proteins from an irradiated surface of 400 μm diameter . Our objective is now to increase the spatial resolution up to µm scale. This requires the characterization of the SMLA mechanism to optimize the ablation yields. We present here recent advances in this field including systematic studies taking into account the physico-chemical parameters of various substrates. Study of the plume dynamics by shadowgraphy is used to optimize the capture yield of the ablated material.  B. Fatou, M. Wisztorski, C. Focsa, M. Salzet, M. Ziskind, I. Fournier, Sci. Rep. 5, 18135 (2015)
Authors : G. Bulai1, S. Irimiciuc2, V. Gafton2, S. Gurlui2
Affiliations : 1 Integrated Center for Studies in Environmental Science for North-East Region (CERNESIM), Iasi, Romania 2 Faculty of Physics, LOA-SL, Alexandru Ioan Cuza University, Iasi, Romania
Resume : The properties of cobalt ferrite (e.g.: high magnetostrictive response and coercive field, mechanical hardness, chemical stability) make them a suitable alternative for the development of sensors and magneto-optic devices while the rare earth (RE) ions can improve the structural and magnetic parameters of spinel ferrites. The aim of our study is to analyze the influence of RE substitution in terms of composition and type on the plasma parameters and structural and magnetic properties of CoFe1-xRExO4 (RE = Gd, Dy, Yb) thin films grown in same conditions by pulsed laser deposition technique. The powders used for target synthesis were obtained by coprecipitation and sintered at 1250oC for 5 hours. The resulting disks were placed in a stainless steel vacuum chamber where a 10-3 Torr base pressure was ensured. The heated (400oC) monocrystalline (100) Si substrate was placed at a distance of 5 cm in front of the target during the 60 min deposition. The Nd-YAG laser (532 nm) fluence was kept at 2 J/cm2. The structural analysis results obtained by XRD, Raman spectroscopy and SEM/EDX technique show the influence of the RE concentration on lattice parameter and crystallinity. The magnetic character of the deposited samples was confirmed by VSM and SQUID. An in-situ plasma analysis was done for all depositions by fast ICCD imaging and space and time resolved optical emission spectroscopy. The obtained results were correlated to the properties of the deposited samples.
Authors : Tsutomu Iwayama, Ken Ogihara
Affiliations : Aichi University of Education
Resume : After first reports on room temperature visible photoluminescence (PL) in the early 1990s, great interest in the optical properties of Si nanocrystals has grown over the last decade because of their potential applications toward Si-based integrated optoelectronic devices. Our group has focused on the formation of silicon nanocrystals, and developed the first examples of luminescent Si nanocrystals inside of SiO2 using ion implantation. Nowadays, different types of Si nanostructures have been synthesized by various method, including chemical vapor deposition, sputtering, pulsed laser deposition, and so on. It is well known that Si nanocrystals produced by various methods show PL peaking in the near infrared or visible spectrum (between 1.4 eV and 1.8 eV).
In this work, we report the optical properties of Si nanocrystals embedded in a SiO2 synthesized by reactive pulsed laser deposition (PLD) in an oxygen atmosphere. Si sub-oxide (SiOx, 0
Authors : F. Stock, L. Diebold, F. Antoni, D. Muller, S. Roques, P. Pfeiffer
Affiliations : ICube, D-ESSP, 23 rue du Loess, 67037 Strasbourg France
Resume : Silicon-germanium (SiGe) quantum dots can be used as high-energy photon converter, known as “red-shift” photoluminescence (PL) in solar cells in order to improve their efficiency. We have demonstrated the possibility to produce SiGe nanoparticles by pulsed laser deposition (PLD) on silicon dioxide substrate. We kept focus on the control of morphological properties of nanoparticles considering various deposition experimental parameters like temperature, fluence and amount of deposited material. Si0.5Ge0.5 controlled ratio was obtained by optimizing the amount of matter ablated successively on Si and Ge pure targets. Rutherford backscattering spectroscopy (RBS) was used to confirm the stoichiometry of the deposited structures. Morphological characterization is performed by Atomic Force Microscopy (AFM) determining average diameter, height and density of the nanoparticles. In order to confirm the crystalline character of the deposited particles, Raman spectra has been made, helping in determining the optimal deposition temperature. PLD allow us to condense a very small and controlled amount of material during the deposition process, permitting this way the growth of nanostructures under a 10 nm range. With these dimensions, SiGe quantum dots are subject to have a photoluminescent behaviour. PL measurements have been made on different sort of deposited nanoparticles. Obtained results have helped us to determine the optimal morphology and density of SiGe particles, permitting an efficient photoconversion for future solar cells applications.
Authors : F. Stock, C. Chowde Gowda, F. Antoni, F. Le Normand
Affiliations : ICube, D-ESSP, 23 rue du Loess, 67037 Strasbourg France
Resume : One of the biggest challenge in optoelectronic devices is the necessity to provide a viable and reliable alternative to transparent conducting oxide (TCO) and especially to Indium thin oxide (ITO). Graphene is a widely studied material and one of the best alternative to be used as conductive and transparent electrodes. It is also well known that the difficulty to transfer graphene on another substrate is a serious limitation for its use on large scale devices. In this work, we explore Diamond-like Carbon (DLC) thin films prepared by pulsed Laser Deposition (PLD) to be used as substrate for graphene-like layers. DLC thin films are excellent candidates due to their high transparency in the visible range remaining also a very good electrical insulator. We already published an important preliminary work in which we studied structural properties like density, sp²/sp3 hybridization ratio as function of UV laser wavelength (193 and 248 nm) and fluences. However, transmission measurements are confirming the UV opaque character of all deposited DLC layers, independently to the experimental parameters used to produce them. Performing uniform surface treatments by flat top UV laser annealing can strongly modify the structure of the DLC thin film in order to bring conductivity to the first atomic layers. Raman spectra of laser annealed DLC samples clearly show the evidence of induced structural changes when compared to untreated samples. The appearance of typical D, G and 2D peaks suggest the presence of graphitic material in the originally pure DLC layer. Optimizing the PLD as well as laser annealing parameters is explored in detail in this work in order to obtain comparable performance (conductivity and transparency) to ITO typical properties. Moreover, using a full-based laser process offers a complete compatibility with all technical steps of the microelectronic area.
Pulsed laser ablation IV : Daniele Pergolesi
Authors : Florin ENESCU1, Stefan-Andrei IRIMICIUC1, Nicanor CIMPOIESU2, Horea BEDELEAN3,Bianca HODOROABA1, Georgiana BULAI4, Silviu GURLUI1
Affiliations : 1Faculty of Physics, LOA-SL, Alexandru Ioan Cuza University, Iasi, Romania 2Faculty of Materials Science and Engineering "Gh. Asachi" Technical University from Iasi, Romania 3Department of Geology, Babes-Bolyai University, Cluj-Napoca, Romania 4Integrated Center for Studies in Environmental Science for North-East Region (CERNESIM), Iasi, Romania
Resume : Studies on the optical emission of plasma plumes generated with laser ablation on unknown geo-material samples are successfully performed for chemical composition and minerals identification. The aim of this study was to investigate how the history of unknown rocks (formation, minerals, and impurities) affects their behavior under high energy laser irradiation. The relations between various plasma parameters (velocity, temperature, etc.) and the nature of the minerals from the rock samples were also investigated. Four rock samples from the Northern hemisphere locations were irradiated by a nanosecond ablation laser within the same experimental conditions with respect to laser fluence and background pressure. The plasma plume dynamics was analyzed by an ICCD fast camera imaging and space-and time-resolved optical emission spectroscopy. The kinetic energy (expansion velocity) of the plasma plume was estimated by ICCD imaging while the plasma thermal energy (excitation temperature) was determined by Boltzmann plot method. Complementary investigations regarding the bulk material were also performed: SEM / EDX for the elemental composition, XRD, RAMAN, and polarized light microscopy for minerals identification. The values of the plasma parameters were discussed with respect to morphological structure of the samples. Possible correlations were found between the excitation temperatures of the atomic and ionic species of the plasmas and the abundance or lack thereof Ca and C related bonds. Strong relations were observed between the global expansion velocities of the plasma plumes and the nature of minerals composing the rocks.
Authors : M. Novotny1, P. Fitl1, J. Vlcek1, J. Bulir1, M. Vondracek1, L. Fekete1, P. Pokorny1, J. Lancok1, S. Guy2, Y. Dekhtyar3, R. Jaaniso4
Affiliations : 1) Dept. of Analysis of Functional Materials, Institute of Physics CAS v.v.i. Na Slovance 1999/2, 182 21 Prague, Czech Republic 2) Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon 69622 Villeurbanne cedex, France 3) Riga Technical University, 1 Kalku str., Riga, Latvia 4) University of Tartu, Ravila 14c, 50411 Tartu Estonia
Resume : ZnO material can be utilized in several emerging applications in optoelectronics and sensors because of its properties, ie. good transparency, high electron mobility, and strong room-temperature luminescence. Trivalent rare earth ions (RE3+) doped ZnO phosphors play important role in such applications. Pulsed UV laser annealing (PLA) is a promising technique to activate and enhance RE3+ emission eliminating undesirable substrate heating. ZnO and ZnO:Eu thin films were grown by Pulsed Laser Deposition (Nd:YAG, λ=266 nm, τ=6 ns) from ZnO and Eu2O3:ZnO targets in either oxygen or nitrogen ambient at room temperature on fused silica substrates. Characteristic Eu3+ emission was only observed at ZnO:Eu films deposited in oxygen ambient (excitation wavelength <310 nm). Ratio of ZnO excitonic band and Eu3+ lines varied with film thickness as well as oxygen pressure. PLA was performed in air ambient using a KrF laser (λ=248 nm, τ=15 ns) at fluence varied from 10 to 200 mJ/cm2. The effect of PLA on optical properties was characterized in-situ by time resolved optical spectroscopy, where another KrF laser (λ=248 nm, τ =6 ns) was used for excitation. Substantial enhancement of both ZnO excitonic band and Eu3+ emission lines was observed. The corresponding variations in the morphology, microstructural properties and chemical composition of the annealed films were measured by AFM, SEM and NanoESCA. Surface roughness substantially increased for PLA treatment at fluence higher than 100 mJ/cm2.
Poster session I : Wolfgang Kautek, Esther Rebollar, David Grojo, Daniele Pergolesi
Authors : A. Taleb (1,2), J. Hermann (1), F. Pelascini (2)
Affiliations : (1) LP3, Aix-Marseille University / CNRS, 13009 Marseille, France; (2) CRITT Matériaux Alsace, 67305 Schiltigheim, France.
Resume : Alloys and glasses are materials of complex composition with large variability of major and minor elemental fractions. Their compositional analysis is therefore a challenging task. Available commercial standard samples do not cover all the compositional domains and glass analyses generally incorporate the time-expensive preparation of matrix-matched standards. Here, calibration-free laser-induced breakdown spectroscopy is foreseen a promising tool, as it enables compositional analysis of materials without the requirement of any standard sample. The analytical performance that calibration-free approaches may access is not yet known. To get a deeper insight in the subject, we characterize the plasma produced by laser ablation of steel and glass. Therefore, fast imaging is applied to observe the expansion dynamics of the ablation plume into the surrounding background gas. Time-resolved optical emission spectroscopy is used to measure temperature and electron density as functions of time. In addition, by comparing the measured spectra to the spectral radiance computed for a plasma in local thermodynamic equilibrium, we deduce the elemental composition and the total amount of material transformed into the plasma state. This amount is compared to the ablated mass that is deduced from volume measurements of the laser-produced craters via optical microscopy. The results are summarized by giving an energy balance for ablation under argon atmosphere and ambient air. A tentative explanation of the low accuracy observed minor element fraction measurements via calibration-free LIBS is proposed.
Authors : Shatha Kaassamani, Wassim Kassem, Michel Kazan, Malek Tabbal
Affiliations : Physics Department, American University of Beirut, Beirut, Lebanon
Resume : Zinc oxide is a II-VI direct band semiconductor (3.37 eV), which has been the focus of intense research due to its potential applications in nano-scale electronics and optoelectronic devices especially in nanostructures and thin film forms. We report here on the synthesis of zinc oxide thin films and nanostructures using the pulsed laser deposition technique (PLD). PLD enables a controlled adjustment of deposition parameters, so ZnO thin films were deposited on c-plane sapphire at different oxygen pressures, substrate temperature, laser energy and repetition rate to study the effect on the crystalline properties and morphology of the resulting films. We demonstrate the growth of high quality crystalline ZnO thin films with preferential orientation along the c-axis. The average crystallite height ranges between 15 and 50 nm with aligned grains. By varying the deposition parameters, we observe different surface morphologies of the ZnO thin films, from smooth surfaces to clusters of grains and lateral growth of nanorods, corresponding to the different growth modes involved in PLD. The residual strain in the films can be tuned from compressive to tensile, and does not depend on the thickness. We observe the formation of ZnO nanowires up to 5 μm in height and 200 nm in diameter. Finally, to study the optical properties of the resulting thin films, UV-VIS transmission measurements were carried out from which the band gap was calculated using a corrected Kramers-Kronig technique.
Authors : Alexandra Palla-Papavlu, Flavian Stokker, Mihaela Filipescu, Valentina Dinca, Maria Dinescu
Affiliations : National Institute for Lasers, Plasma, and Radiation Physics, Magurele, ZIP 077125, Romania
Resume : Sensors and biosensors play a leading role in devices and systems destined for human health and safety. However, most of the existing sensor based systems require complicated electronic structures and high manufacturing costs. Therefore, cheap devices on light, flexible substrates are required. This work deals with the design, fabrication, and characterization of a flexible, wearable, and low cost sensor suited for on-body physiological monitoring based on nanocomposite materials (polymers and graphene) and fabricated by laser-induced forward transfer (LIFT). Conventional LIFT consists of the irradiation, using a pulsed laser, of a thin layer of an absorbing material (the donor) that has been deposited onto a transparent substrate. The layer is irradiated through the substrate and the light-matter interaction which takes place at the interface generates a strong increase of the local pressure. As a result, a small piece of the thin film located above the irradiated area is ejected (as a pixel) from the substrate surface and deposited onto a target substrate (the receiver) arranged in close proximity to the donor substrate. The size of the ejected material is controlled by the size of the incident laser spot. In this work, 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, i.e. below 100 µg/L 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 : E. Millon 1, V. Roge 1, C. Cachoncinlle 1, J. Perriere 2,3, E. Briand 2,3
Affiliations : 1 GREMI, UMR 7344 CNRS / Universite d’Orleans, 14 Rue Issoudun, F-45067 Orleans 2, France 2 Sorbonne Universités, UPMC Paris 06, UMR 7588, INSP, 4 Place Jussieu, F-75005 Paris, France 3 CNRS, UMR 7588, INSP, 4 Place Jussieu, F-75005 Paris, France
Resume : Magnetite (Fe3O4) and wustite (FeO) are well-known oxides for their tremendous magnetic properties. However, being able to grow stable FexOy thin films with controlled iron oxidation states could be of interest for further applications. In this work, we highlight the formation of different FexOy based thin films grown by pulsed laser deposition (PLD) from Fe or Fe3O4 targets onto sapphire or MgO substrates. Based on XRD and RBS analysis, we point out that, by controlling both the substrate temperature and the oxygen pressure in the 10-7 – 0,1 mbar range during the PLD growth, films with various Fe/O ratios may be prepared. Thus, the different crystalline phases of the Fe-O system may be obtained: Fe2O3, Fe3O4, and the thermodynamically metastable FeO. In particular we show that at low pressure (10-6 mbar) Fe3O4/Fe composite thin films for which both metallic Fe and Fe3O4 phase are epitaxially grown on the sapphire substrates even at room temperature. This result is interpreted as a possible phase separation from the FeO metastable phase. The precise growth conditions leading to the formation of FeO-based film are also discussed.
Authors : Ro.G. Nikov1, N.N. Nedyalkov1, A.Og. Dikovska1, 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 complex ZnO and ZnO/noble metal colloidal nanostructures. The method involves two steps. In the first one, nanostructures are deposited by standard pulsed laser deposition technique on a quartz substrate. In the second step, the as-prepared samples are irradiated by nanosecond Nd:YAG laser in distilled water. The possibility of transferring of the initial nanostructure into the liquid is demonstrated. The influence of different laser processing parameters on the characteristics of the colloidal solutions is studied. Transmission electron microscopy and selected area electron diffraction are employed for revealing the morphology and identification of the phase composition of the created nanostructures. The optical properties of the produced colloids are evaluated by optical transmittance measurements in the UV–VIS spectral range. The presented method could be an efficient alternative to the chemical methods for fabrication of complex metal-oxide nanostructures composed colloids with possible application in biotechnology, photonics, and catalysis.
Authors : Ru.G. Nikov, A.Og. Dikovska, N.N. Nedyalkov
Affiliations : Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, Sofia 1784, Bulgaria
Resume : This study presents a laser-assisted method for fabrication of oriented nanowires composed by nanoparticles. The technology is based on an implementation of the pulsed laser deposition (PLD) process in an open-air atmosphere in the presence of a magnetic field. Ablation of an iron oxide target was performed by nanosecond laser pulses delivered from Nd:YAG laser system oscillating at 1064 nm. Due to the high density of the ambient, nanoparticles and nanoparticle aggregates were formed by condensation in the plasma plume. The application of an external magnetic field on the ablated material resulted in an arrangement of the nanoparticles on the substrate forming long (few microns) nanowires with an orientation parallel to the magnetic lines of force. The dependence of the morphology of the produced structures on the process parameters as laser wavelength, laser fluence, target-to-substrate distance and orientation of the magnetic field was investigated. The presented structures could be used in the design of novel nanoelectronics, spintronics, and magneto-optics devices.
Authors : G. Dorcioman1,2, E. Axente1,2, F. Sima1, D. Craciun1, P. Garoi1,2, C. Hapenciuc1, V. Craciun1,2
Affiliations : 1National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania; 2DENTIX MILLENNIUM SRL, Sabareni-Ilfov, Romania
Resume : The aim of the work reported here is the growth of titanium oxide films and nanostructures starting from either metallic Ti or TiO2 targets using the pulsed laser deposition (PLD) technique. The depositions were carried out in different atmospheres (vacuum, Ar or O2) and at room temperature (RT) or 300 °C. To promote crystallization, some of the films underwent a post deposition treatment at different temperatures in the range (150-300 °C). The structure point of the obtained films was investigated by grazing and symmetrical incidence X-ray diffraction. The surface morphology was studied by scanning electron microscopy and atomic force microscopy. Also, the chemical composition of the deposited films was investigated using X-ray energy dispersive and X-ray photoelectron spectroscopies. The electrical characteristics of the deposited films were measured by a four point probe technique and optical properties were obtained from transmission measurements in the 190-3000 nm. Wettability studies completed the surface characterization of these films. The results showed that the nature and pressure of the gaseous atmosphere during deposition controlled the films structure, stoichiometry and properties. Films contained mixtures in various ratios of metallic Ti and different oxides, starting from Ti3O up to the stable rutile TiO2. The surface morphology, apart from the usual droplets found in PLD grown films, was generally smooth, although for the 0.5 mbar O2 pressure a strong texturing and higher rms values were observed. Most interestingly, the wettability of these films could be controlled from hydrophobic to hydrophilic, which could have interesting applications for medical implants made from Ti or Ti alloys.
Authors : Jeeyoung Lee, Yoonseok Oh, Minseok Seo, Jaeyong Kim, Seonwu Lee, and Myeongkyu Lee
Affiliations : Yonsei university
Resume : Metal nanoparticles have a wide variety of application areas including electronic devices, displays, solar cells, and biosensors. In particular, gold nanoparticles have attracted significant attention due to their superior biocompatibility and unique optical properties. The distinct surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) effects of Au nanoparticles can be effectively utilized in biomedical sensing and imaging. To achieve distinctive optical signals, these particles should be uniform in shape and size. Various chemical methods have been developed to control the size and shape of metal nanoparticles, however, they are often energy-intensive, employ toxic chemicals, and require high temperatures. We show that Au nanopowders with arbitrary shapes can be converted into nanoparticles with a narrow size distribution by using a nanosecond Nd:YAG laser. Commercial Au powders were first dissolved in deionized water and irradiated with laser pulses at 532 nm. This converted the powder clusters into spherical particles with sizes ranging from 100 nm to a few micrometer. Subsequent irradiation of these Au spheres with 1064 nm pulses produced a larger quantity of nanoparticles with fairly uniform sizes. The overall conversion process could be well explained by the photothermal melting-evaporation mechanism. The fabricated Au particles exhibited a mean size of 15 nm, with a standard deviation of 5.5-7.2 nm. The Au colloidal solution was highly stable against agglomeration, and the particles remained well-dispersed in water for 1 month. This behavior is attributed to surface charges introduced during the laser process.
Authors : María Sánchez-Arenillas, Juan de la Figuera, José F. Marco, Marta Castillejo, Mohamed Oujja
Affiliations : Instituto de Química Física Rocasolano (CSIC), C/ Serrano 119, Madrid 28006, Spain.
Resume : Cobalt ferrite has attracted interest in various fields such as high-temperature superconductivity, spintronics, microelectronics and magnetic applications. Cobalt ferrite is a mixed iron (III) and cobalt (II) oxide with a spinel-related structure. Our work is focused on understanding the growth of cobalt ferrite thin films on Si (100) by pulsed laser deposition (PLD). The study is aimed at investigating the influence that deposition parameters such as substrate temperature, target-substrate distance or oxygen partial pressure have on the physicochemical properties of the obtained films and, in particular, in cation oxidation states, cation distribution and crystal quality. For this goal we have used characterization techniques such as X-ray Photoelectron Spectroscopy, Raman spectroscopy, Mössbauer spectroscopy, X-Ray diffraction, low-energy electron diffraction and atomic force microscope. The results indicate that deposition using laser irradiation wavelengths in the infrared (1064 nm, repetition rate of 10 Hz, 6 ns pulses), target-substrate distances in the range 2-4 cm, partial oxygen pressure of 10-4 mbar and a substrate temperature of 540 oC produce the best thin films, with properties similar to those of the target. Lower oxygen pressures, larger distances between target and substrate and lower substrate temperatures produce either more reduced/less crystalline phases or both. This work is funded by projects CTQ2016-75880-P and MAT2015-64110-C2-1-P (MINECO, Spain).
Authors : G. Atanasova1, A. Og. Dikovska2, T. Dilova1, P. Stefanov1, 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 : In this work, we present the preparation of metal-oxide nanostructures by pulsed laser deposition (PLD) in air at atmospheric pressure (in open air). The technology applied 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. Our attention was focused on the gas-sensing properties of different metal-oxide samples, such as ZnO, TiO2, SnO2 and MoO3. The samples were exposed to pollutants and toxic gasses, namely, CO, NH3, NO2, as well as to VOCs. The technology presented for fabrication of sensor elements offers an easy way of adding other elements for doping purposes. The enhanced sensitivity and selectivity of the samples was demonstrated by fabrication of nanocomposite samples consisting of metal-oxide and noble-metal (Au or Pd) nanoparticles. 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 Program „Competition for financial support for project of junior researchers and postdocs – 2017” of the National Science Fund, Ministry of Education and Science of Bulgaria.
Authors : M. Filipescu, N. L. Dumitrescu, S. Brajnicov, D. Colceag, V. Ion, M. Dinescu
Affiliations : National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor St, RO-077125, Magurele, Romania
Resume : Improving the knowledge on tritium effects in different components in fusion facilities is an important issue. Commonly deuterium is used to replace tritium in simulation experiments. This work aims to study the deuterium doping effect on tungsten and aluminum properties. Thin films of W and Al doped with D2 were obtained by pulsed laser deposition (PLD) and radio-frequency assisted pulsed laser deposition (RF-PLD) techniques in deuterium atmosphere. The influence of the radiofrequency discharge on the amount of deuterium present in the layers and on the doping effects was evidenced by X-ray diffraction, atomic force microscopy, secondary ion mass spectrometry, spectroellipsometry. Acknowledgement: Financial support from the Romanian National Nucleu Program and TRANSAT 754586 is gratefully acknowledged.
Authors : Angela De Bonis, Agostino Galasso, Alessandro Latini, Julietta V. Rau, Antonio Santagata, Roberto Teghil
Affiliations : Angela De Bonis; Agostino Galasso; Roberto Teghil Dipartimento di Scienze, Universita della Basilicata, Via dell'Ateneo Lucano 10, 85100 Potenza, Italy. Alessandro Latini Dipartimento di Chimica, Universita di Roma la Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy. Julietta V. Rau Istituto di Struttura della Materia, Consiglio Nazionale Delle Ricerche, Via del Fosso del Cavaliere 100, 00133 Rome, Italy. Antonio Santagata Istituto di Struttura della Materia, Consiglio Nazionale Delle Ricerche, UOS Tito Scalo, C/da S. Loja, Tito Scalo, Potenza, Italy
Resume : Transition metal borides have received a large scientific and technological interest in the last years, due to their peculiar chemical-physics and mechanical properties. Among these compounds chromium borides are promising candidates for several structural applications, in particular as protective coatings for materials exposed to corrosive and abrasive environments. In this paper the pulsed laser deposition of chromium diboride thin films has been carried out in vacuum by using a frequency doubled Nd:glass laser with a pulse duration of 250 fs. The films have been deposited at different substrate temperatures and characterized by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. The results indicate that only the film deposited at a substrate temperature of 500 °C are crystalline and formed by chromium diboride, suggesting a process involving a deposition from plasma condensation. This hypothesis has been confirmed by the study of the plasma produced by the ablation process. Finally, the films hardness has been studied by Vickers indentation technique.
Authors : Hisham Forrière (1), Eric Halter (1), Pierre Pfeiffer (1), Christophe Cordier (1,2), Thierry Engel (1,2), Manuel Flury (1,2)
Affiliations : (1) Laboratoire des Sciences de l’Ingénieur, de l’Informatique et de l’Imagerie (ICube), UDS-CNRS, UMR 7357, 300 bd Sébastien Brant, CS 10413, F-67412 Illkirch cedex, France (2) Institut National des Sciences Appliquées de Strasbourg (INSA Strasbourg) – 24 Boulevard de la Victoire, 67084 Strasbourg Cedex, France
Resume : We will present laser treatments of specific materials used for additive manufacturing and 3D Printer with a high energy laser emitting at 532 nm. The laser was a Quantel Q-Smart 850 with a pulse size of 5 ns and 10 Hz frequency, containing a frequency doubler. The two studied materials were mainly VeroWhite Plus FullCure 835 from Stratasys Objet 30 Prime Printer and the Visijet M3 Crystal for Projet 3510 commercialized from 3D Systems or PLA Filament for Vellemand Kit. We focalized the laser source with a simple spherical lens to see how the laser can bore, or excavate material without problems and destruction. The two materials have very unusual optical and physical properties: the verowhite is very porous and containing many particles, whereas the visijet is clear but it is a diffuse material. We made also measurements with a commercial optical Interferometer Newview 5200 from Zygo to measure the hole depth and see the exacte profile of the crater. We made also profilometry of other Full Field house made optical coherence tomography system. This measurements allow us to estimate the ablation rate versus the shot number.
Authors : Stefan Andrei Irimiciuc1, Georgiana Bulai2, Maricel Agop3, Silviu Gurlui1
Affiliations : 1Faculty of Physics, Atmosphere Optics, Spectroscopy and Lasers Laboratory, “Alexandru Ioan Cuza” University of Iasi, 700506 Iasi, Romania 2 Integrated Center for Studies in Environmental Science for North-East Region (CERNESIM), Iasi, Romania 3Department of Physics, “Gh. Asachi” Technical University of Iasi, 700050 Iasi, Romania
Resume : Experimental investigations were performed on ns laser ablation plasma on metallic targets (Al, Ag-Cu alloy). The dynamics of the plasma plumes were investigated in situ by ICCD fast camera imaging and space-and time-resolved optical emission spectroscopy (OES). The fast camera imaging revealed the splitting of the plume into two plasma structures expanding with different velocities, while the OES measurements revealed strong fluctuation in the spatial distribution of the excitation temperature determined by Boltzmann plot method. The temperature fluctuations are related to the plasma oscillatory behavior, recently showcased in the laser ablation community. The angular distribution of the plume front velocity was determined and revealed a segregation of the alloy generated plasma based on its components. The results are discusses in conjecture with the bonding energy of the metallic ions in the crystalline lattice and the scattering effects during plume expansion. Post deposition investigations were performed on both targets and thin films by means of SEM/EDX and Raman techniques. The results indicated the non-congruent transfer from the alloy target, as the final thin film was found to be depleted of Cu. This is in a good agreement with the plasma plume behavior, too. A scattering theoretical model was developed in the framework of a fractal hydrodynamic approach. The model aims to envelop the dynamics of plasma particle in complex targets in relation with the mean free path and scattering probability for each species. The results concerning the angular distribution of the ejected species during expansion, are in good agreement with the experimental data.
Authors : E. Iordanova1, G. Yankov1, N. Nedyalkov2, L. Kovachev2, N.E. Stankova2
Affiliations : 1 Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd.,1784 Sofia, Bulgaria; 2 Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko chaussee blvd., Sofia 1784, Bulgaria
Resume : The current work concerns investigation on noble metal doped glass materials radiated by femtosecond laser pulses. The motivation of the research is based on the specific properties of noble metal nanoparticles and their applications. The main part of the applications is related to their unique optical properties. In this study are observed filament formations in Au ion doped glass materials during the irradiation by femtosecond laser pulses. The second harmonic generations in the media are observed as well. This proves the formation of crystal structures inside the media after femtosecond laser radiation. Nonlinear effects of the glass samples are investigated in terms of the laser beam parameters. The laser energy applied is between 10 and 40 μJ. The wavelengths used in the experiments are between 240 to 2600 nm, generated by optical parametric amplifier system (TOPAS). The regenerative Ti:Sapphire amplified laser system emits at 800 nm central wavelength with a pulse duration of 35 fs and 1 kHz repetition rate. The nonlinear refractive index n2 and multiphoton absorption β are measured.
Authors : L. Kolaklieva1, V. Chitanov1, K. Antonova2, P. Terziyska2, A. Szekeres2, P. Petrik3, Zs. Fogarassy3, A. Romanenko3, L. Duta4, I. N. Mihailescu4
Affiliations : 1-Central Laboratory of Applied Physics, Bulgarian Academy of Sciences, 59 St. Petersburg Blvd., 4000 Plovdiv, Bulgaria 2-Institute of Solid State Physics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, Sofia 1784, Bulgaria 3-Centre for Energy Research, Hungarian Academy of Sciences, Konkoly-Thege út 29-33, H-1121 Budapest, Hungary 4-National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, 077125 Magurele, Romania
Resume : We report a study of the relation between mechanical, optical and structural properties of Aluminum nitride (AlN) thin films, synthesized on Si substrates by pulsed laser ablation (PLD) at different deposition conditions. The AlN films are nanostructured and thus alteration of mechanical and optical properties with films structure are expected. A pulsed KrF* excimer laser source (lambda=248 nm, pulse duration less than 25 ns, incident fluence ~3 or 10 J/cm2) was used to ablate AlN target with pulse repetition rates of 3, 10 and 40 Hz, and at nitrogen pressure of 0.1, 5 or 10 Pa. The substrates were heated up to 800 °C, 450 °C, 400 °C or 350 °C. The mechanical properties of the films are investigated by Berkovich nanoindentation induced deformation in the loading interval 5-100 mN. The PLD AlN films exhibit enhanced mechanical hardness. The nanoindentation tests yielded hardness in the range of 22-27 GPa and Young’s modulus of 230-280 GPa. Those values are related to the AlN film structure that consists of nanocrystallite grains the development of which strongly depends on deposition parameters. The optical constants values, ellipsometrically obtained, higher than that typical for amorphous AlN infer the existence of crystallites in the amorphous film matrix. The latters are visualized by TEM imaging and proved by FTIR spectra’ analysis, which shows characteristic Reststrahlen band of h-AlN lattice with component lines arising from IR active phonon vibrational modes in AlN nanocrystallites.
Authors : R.Pascu1, G. Epurescu1, A. Vlad1, R.Radu2, A. Matei1
Affiliations : 1. National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Str., P.O. Box MG-36, 077125, Magurele, Bucharest, Romania 2. National Institute for Materials Physics, Atomistilor Str.405A, P.O. Box MG7, 077125, Magurele, Bucharest, Romania
Resume : Thin films aluminum oxide/ yttria stabilized zirconia (alfa - Al2O3/8mol% YSZ) are produce on Si and quartz substrates by PLD from sintered targets in O2 atmosphere. The alfa- Al2O3/ 8YSZ thin films have applications in developing of advanced low conductivity thermal barrier with high stable phases. PLD films gather a combination of mechanical and electrical properties for a wide range of applications. Structural and optical characterizations are performed by SEM, XRD, AFM, XPS and spectroscopic ellipsometry. The electrical parameters are measured in air.The structure is influenced by controlling the oxygen pressure, the target- substrate distance and the laser fluence. The effect of microstructure of thin alfa- Al2O3 layer on 8 YSZ is studied to improve the mechanical stability limits of thermal barrier to avoid delamination by controlling the oxygen pressure, the target – substrate distance and laser fluence; columnar 8YSZ thin film provides a technique for compensation of thermally expansion during heating. Key words: Thermal barrier, by- layer planar alfa- Al2O3/ 8YSZ, PLD, Optical, structural and electrical characterization.
Authors : A. Andrei1, N. D. Scarisoreanu1, V.Ion1, R. Birjega1, N.Dumitrescu1, F. Craciun2, M. Dinescu1
Affiliations : 1 NILPRP, P.O. Box MG-16, RO-77125, Bucharest, Romania 2 CNRISC, Istituto dei Sistemi Complessi, Via del Fosso del Cavaliere 100, I-00133, Rome, Italy
Resume : The bismuth based materials seem to be an attractive candidate for lead free materials. In this context, sodium bismuth titanate Na0.5Bi0.5TiO3 (NBT) was considered to be one of the most promising aspirants to replace lead based materials. In the present work, we investigate the optical, structural, dielectric and ferroelectric properties of NBT-BT thin films obtained by pulsed laser deposition as a function of composition, from pure NBT across and beyond morphotropic phase boundary (MPB) (x=0, 0.06, 0.08). An enhanced stability of ferroelectric phase in thin films with respect to bulk has been observed for specific compositions within the MPB, explained by their peculiar microstructure. For NBT-BT (x=-0.06) thin films, a classic switching behavior has been noticed and the locally measured value of effective piezoeletric coefficient d33eff was 83 pm/V which is higher than the previously reported values for pure NBT or lead-based thin films. Dielectric and ferroelectric measurements were performed using an impedance analyzer HP 4294A and RT 66A Ferroelectric Test System. XRD, SEM, HR-TEM and AFM techniques have been used for morphologic and structural characterizations of NBT-BT films. Pyroelectric properties were investigated with a Woollam Variable Angle Spectroscopic Ellipsometer (VASE) system under different temperature conditions.
Authors : M. E. Koleva1, N. N. Nedyalkov1, L. Aleksandrov2, R. Iordanova2
Affiliations : 1Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee blvd., Sofia 1784, Bulgaria 2Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev str., Bl 11, Sofia, 1113, Bulgaria
Resume : The interaction of light with nanocomposites reveals novel optical phenomena indicating unrivalled optical properties of these materials. Nanomaterials have drawn great attention because of their distinguishable optical properties such as appearance of prominent absorption bands via surface plasmon excitation. The present study focuses on the synthesis of noble metal nanoparticles and how these particles can be incorporated and manipulated in thin film oxides. The structural and functional properties of the nanoparticles when embedded in a glass host matrix are covered by this research. The effect of laser and thermal annealing procedures on the behaviour of laser fabricated composite nanostructures in investigated. The coloration of samples is determined by the nano-sized metal particles in a dielectric matrix, due to a surface plasmon resonance effect of the conductive electrons and respective selective absorption. The laser deposition and annealing are performed by a nanosecond Nd:YAG laser systems (Lotis) at third and fourth harmonics, with the pulse repetition rate of 10 Hz and the pulse duration of 12 ns. The experimental results indicate that the annealing induces a red-shift of the transmission dip. The tuning of optical properties of the samples was interpreted as a function of their morphology and structure, formed at certain parameters in the processing stages of deposition and annealing.
Authors : M. Gansukh1, S. Engberg1, N.C. Schjødt2, S. López-Marino3, J. B. Pedersen1, O. Hansen3, N. Pryds4, J. Schou1 and S. Canulescu1
Affiliations : 1 DTU Fotonik, Technical University of Denmark, DK-4000 Roskilde, Denmark 2Haldor Topsoe A/S, Haldor Topsøes Allé 1 DK-2800 Kgs. Lyngby, Denmark 3DTU Nanotech, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark 4DTU Energy, Technical University of Denmark, DK-4000 Roskilde, Denmark
Resume : Chalcogenides as Cu2ZnSnS4 (CZTS) are of high interest for technological applications as absorber layers for thin-film solar cells. Previous studies on laser ablation of CZTS have shown that the composition of the films can be controlled in-situ by tuning the laser fluence. In this study, we compare films obtained with multicomponent oxide- and sulfide-based targets for CZTS solar cells using different PLD conditions. The as-deposited films exhibit a Cu/(Zn+Sn) metallic ratio varying from 0.7 to 1.0 by changing the laser fluence from 0.7 J/cm2 to 3.5 J/cm2 on both oxide and sulfide targets. The as-deposited films of Cu-Zn-Sn-O and Cu-Zn-Sn-S are subsequently annealed at a temperature of 5500C in a sulfur atmosphere. The advantage of using oxide films is that Sn losses during the annealing should be less as compared to the more volatile sulfide counterparts. By using oxide films of Cu-Zn-Sn-O that are post-sulfurized, it is possible to achieve high quality CZTS films. Our data indicate that the oxygen content in the annealed CZTS films both from oxide and sulfide films is comparable. Raman, photoluminescence and XRD analyses show that high quality crystalline films are formed from oxide precursors after the annealing. The films and solar cells produced from both oxide and sulfur precursors routes are compared in terms of structural, optical, electrical and morphological properties.
Authors : V. Ion1, N. D. Scarisoreanu,1, A. Andrei1, A. Bonciu1,2, A. Moldovan1, M. Dinescu1
Affiliations : 1National Institute for Laser, Plasma and Radiation Physics, Magurele, Bucharest, Romania 2Faculty of Physics, University of Bucharest, Magurele, Romania
Resume : Devices developed for aeronautic or space industry must be able to operate in harsh environments, where the mechanical stress and temperature gradients are high. In order to protect those devices, various coating techniques and materials were developed. In our work, we report on multilayer structures obtained by pulsed laser deposition. Heterostructures of Al2O3/SiC and Yttria stabilized zirconia YSZ/SiC were deposited on silicon and alumina substrates. A parametric study on the influence of substrate temperature, multilayer composition and the deposition gas pressure on the properties of the coating properties was carried out. Crystalline properties and topography of coating’ surfaces were studied using X-ray diffraction (XRD) and atomic force microscopy (AFM). 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 : Pierre Lorenz1, Michael Klöppel2, Igor Zagoranskiy1, Frank Frost1, Klaus Zimmer1
Affiliations : 1 Leibniz Institute of Surface Engineering, Permoserstraße 15, 04318 Leipzig, Germany; 2 Fraunhofer-Institut für Verkehrs- und Infrastruktursysteme IVI, Zeunerstraße 38, 01069 Dresden
Resume : The fast and cost-effective laser patterning of thin metal films with lateral sizes below the diffraction limit is still a challenge but self-organizing processes are therefore of special interest. The ns laser-induced metal nanopattern formation process enables the fabrication of randomly distributed sub-µm metal structures, like droplets, due to the laser-induced melting of thin metal layers. The lateral confinement of the metal film achieved by lithographic patterning allows the tuning of the pattern arrangement from randomly distributed, unequal sized patterns to quasi periodically arrangements and finally to determined structures due to the reduction of the lateral size of the initial metal structures below the liquid film instability limit. In this study, we examine the interaction of KrF excimer laser pulses (248 nm and 25 ns) with photolithographic produced chromium squares (side length 1 – 5 µm, film thickness 10 -50 nm) on fused silica. The irradiation of these substrates with the metal squares leads to melting, mass transport due to the surface tension in the metal liquid phase and finally a nano pattern formation after resolidification of the molten metal from the squares. The patterns were examined by scanning electron (SEM) and atomic force microscopy (AFM). Furthermore, the process was simulated considering the heat equation and the Navier-Stokes equation for describing laser heating and melting and the mass transport in the liquid phase, respectively.
Authors : Mindaugas Juodėnas1, Tomas Tamulevičius1,2, Justas Deveikis2, Audronė Pabalytė2, Šarūnas Meškinis1, Abdel-Aziz El Mel3, Pierre-Yves Tessier3, Sigitas Tamulevičius1,2
Affiliations : 1Institute of Materials Science, Kaunas University of Technology, K. Baršausko St. 59, LT-51423 Kaunas, Lithuania 2Department of Physics, Kaunas University of Technology, Studentų St. 50, LT- 51368 Kaunas, Lithuania 3Jean Rouxelle Institue of Materials, University of Nantes, Chemin de la Houssinire, Nantes 44300, France
Resume : Over the years, great strides have been made by the laser micromachining industry in quality, performance, and cost areas. When used as a patterning tool, ultra-short pulse lasers have become a serious contender for the well-established clean-room based techniques. Both the quality of available structures and resolution have come close and can even surpass the capabilities of conventional lithography. Therefore, exploitation of photon-assisted nanostructuring techniques, which often are single-step operations compatible with a full spectrum of materials, is relevant and well worth the effort. In this work we present our research based on femtosecond laser microstructurisation of metal surfaces, i.e. direct laser interference patterning and focused beam ablation. We used these techniques for several relevant applications: copper diffraction gratings for efficient light trapping in photodetectors, copper microstructures for seeded nanowire growth, arrays of diffraction gratings, i.e. dot-matrix holograms on nickel foil for optical security measures. We cover such aspects of research as intended structure modelling, laser patterning, technological parameter optimization, characterization of achieved structures, etc. Our results showcase the capabilities of laser patterning technology as an emerging alternative for conventional lithography on a variety of materials and with a quality that is high enough for the patterned nanostructures to be used in practical applications.
Authors : J. Panigrahi, E. Terrier, S. Cho, V. Halté
Affiliations : IPCMS, CNRS-Université de Strasbourg,Strasbourg (FRANCE); Ulsan University, South Korea
Resume : A few years ago, it has been demonstrated that three-Fe-sites lattice distortions called trimerons play a major role in the insulating phase of Fe3O4. More recently time-resolved X-ray diffraction and optical reflectivity on bulk magnetite show how these trimerons are affected in the out-of-equilibrium Verwey transition induced by ultrashort lasers pulses. Here, we show the very first time-resolved magneto-optical study in thin Fe3O4 film as a function of temperature across the Verwey transition. Both ultrafast charges and spins dynamics allow us to identify the metal-insulator transition through their main temporal features. In particular, we show that precession behavior is associated to a non-trivial modification of time-dependent effective field across the Verwey transition and is correlated to a transient mixed phase induced by ultrashort pulses.
Authors : A. N. Nikolov (1), N. E.Stankova (1), I. I. Balchev (1), E. L.Pavlov (1), N. N. Nedyalkov (1), D. B. Karashanova (2)
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 : An electric field was applied during the process of pulsed laser ablation of Au and Ag targets immersed in double-distilled water using a Nd:YAG laser operating at different wavelengths and fluences, thus forming various colloids. The ablation was performed by the fundamental (λ = 1064 nm), and the second (λSHG = 532 nm) and third (λTHG = 355 nm) harmonics of the laser system. The changes in the size and shape of the nanostructures were investigated as a function of the angle between the direction of the electric field applied and that of the laser beam propagation. Further, the effect was explored of the electric field on the formation of the nanowire network. The size distribution of the fabricated colloids was modified by post irradiation in the presence of an electric field; the effect was followed of varying the field’s parameters on the colloid’s characteristics. The optical transmission spectra of the colloids were employed for indirect assessment of the nanostructures’ size and shape variation. The colloids were visualized by transmission electron microscopy (TEM), while the structure and phase composition were examined by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED).
Authors : Ilhem. R. KRIBA1*; A. DJEBAILI2; z. SKANDERI2
Affiliations : 1 Plasma Laboratory - Faculty of Sciences ? University of Batna 2- Algeria 2 Laboratory of chemistry and environmental chemistry L.C.C.E - University of Batna- Algeria
Resume : Plasma spray deposition is one of the most important technologies available for producing the high-performance surfaces required by modern industry. In this process, powder of the coating material is fed into high-temperature plasma, which melts and accelerates the powder; the molten particles subsequently hit and solidify on the surface to be coated. Most of the applications require coatings with a high density, which are well bonded to the substrate. To obtain good quality coating, the powder particle must be at least partially molten and hit the substrate with a high velocity. Since plasma spray equipment is expensive to operate, the cost of developing new coatings can be very high. A computer model capable of predicting the coating properties as a function of process parameters will greatly reduce the development time and cost. The 2D computational fluid dynamic technique have been applied to analyze the impacting process and the subsequent temperature fields of two molten ceramic particles in order to tackle the most complete heat transfer and solidification problem in order to characterize the overall coating. Keys words: Plasma spray process; molten ceramic; coating properties; fluid dynamic technique
Authors : J. Valenta (a), M. Greben (a), T. Zikmund (b), J. Lancok (b)
Affiliations : (a) Faculty of Mathematics & Physics, Charles University, Prague, Czechia. (b) Institute of Physics, Czech Academy of Sciences, Prague, Czechia.
Resume : Advanced methods of optical spectroscopy have been developed and applied to study optical properties of various lanthanide-doped fluoride materials. The spectral distributions of quantum yield (QY), power efficiency (PE) and onset / decay kinetics of luminescence under excitation at 978 nm can be determined with our set-up. The excitation beam is continuous or modulated into square-shaped pulses using an acousto-optical modulator. Emission is coupled to the double-parallel-detection-paths spectroscopic system covering broad spectral range from UV to NIR (360-1650 nm), which enable to observe both up-converted and down-converted emission and detect signal separately for each emission band . The technique is applied to study various doped fluoride materials: Na(Y,Lu,Gd)F4 codoped by Yb3+ and Er3+, Tm3+, or Ho3+ and Pr3+:CaF2 codoped by Yb3+ or Eu2+ as sentitizers . The typical slow (order of ms) onset and decay kinetics of the main emission bands are described by a set of differential equations. The fitting of experimental datasets with this model gives deep insight into the energy transfer processes. (The work is funded by the CSF, project 16-22092s)  J. Valenta and M. Greben, AIP Adv. 5 (2015) 047131.  A.Guille et al., J. Appl. Phys. 114 (2013) 203509.
Authors : Jan Rosigkeit, Peter Staron, Florian Pyczak, Martin Müller
Affiliations : Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Germany
Resume : We are currently developing a new industry-relevant sample environment purposefully designed for time-resolved in situ selective laser melting (SLM) studies using high-energy (30−200 keV) and high photon flux synchrotron radiation. The high photon flux combined with a new fast-acquisition-time (4 ms) 2D-detector for high photon energies permits time-resolved in situ structural analysis of the selective laser melting process. The high-energy synchrotron-radiation based X-rays result in small scattering angles (<8°), allowing large areas of reciprocal space to be imaged with a 2D detector. The device for in situ experiments (FlexiSLM) is planned for use at the P07 High Energy Materials Science (HEMS) beamline at the synchrotron radiation source PETRA III at the Deutsches Elektronen-Synchrotron (DESY) in Hamburg.
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Laser interaction with matter: fundamentals and applications I : David Grojo
Authors : J. Hoyo, R. Meyer, R. Giust, C. Billet, L. Furfaro, F. Courvoisier
Affiliations : FEMTO-ST Institute, Université de Bourgogne-Franche-Comté UMR CNRS 6174, 25030 Besancon, France
Resume : Direct laser writing is a very useful technique to process dielectrics for many applications, like micro-fluidics, photo-electronics or glass cutting for consumer electronics. Material processing requires accurate control on energy deposition profiles inside the transparent material, which strongly depends on irradiation conditions. Gauss-Bessel beams have been successfully used for ultra-high aspect ratio processing because of the enhanced stability of these beams in comparison with the unstable and complex filamentation regime of Gaussian beams . In this work, we temporally split the input 100 fs laser pulse in two equal pulses with a variable delay. We compare single and double pulse illumination as a function of delay on the drilling of high aspect ratio nanochannels in borosilicate glass. Our main result is that, with equal energy, splitting the pulse allows increasing the channel width and enables channel drilling for conditions when only index modification was created. The results strongly depend on the sub-nanosecond delay (ie at delays below the standard burst mode of lasers). We report measurements of energy absorption and interpret our results in terms of confinement of the energy deposition. Our results raise novel fundamental questions on laser-matter interaction and we anticipate a wide impact on technological applications to laser processing of transparent materials.
Authors : Sergej Orlov, Alfonsas Juršėnas, Ada Gajauskaitė, Vitalis Vosylius, Pavel Gotovski, Artūras Grabusovas, Justas Baltrukonis, Ernestas Nacius, 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 : Beam profile engineering, where a desired optical intensity distribution can be generated by an array of phase shifting (or amplitude changing) elements is a promising approach in laser material processing. For example, a spatial light modulator (SLM) is a dynamic diffractive optical element allowing for experimental implementations of controllable beam profile. Scalar Mathieu beams have elliptical intensity distribution perceivable as “optical knives” in the transverse plane. On the other hand scalar Weber beams have a parabolic cross-section, which enables us to call them “optical showels”. Both families exhibit non-diffracting properties similar to Bessel beams, where a relatively long focal depth retains unchanging intensity distribution, which makes them a promising approach in laser processing. Here, we introduce vector versions of those beams with controllable polarization and investigate numerically their spatial spectra. We use vector Mathieu and Weber beams as a basis to construct controllable on-axis phase and amplitude distributions with polarization control. Further, we attempt to generate components of vector Mathieu beams experimentally using SLMs and report on our achievements in the control over the beam shape and dimensions along the propagation axis. Lastly, we discuss generation of femtosecond pulsed “knive” and “shovel” type beams using geometric phase elements, made with laser induced nanograting ripples in fused silica and produced by “Altechna R&D”.
Authors : Grégoire R. Chabrol(1,2), Robin Pierron(2), Stéphane Roques(2), Yoshitate Takakura(2), Patrice Twardowski(2), Pierre Pfeiffer(2), Sylvain Lecler(2)
Affiliations : (1) ICube UMR CNRS, ECAM Strasbourg-Europe; (2) ICube UMR CNRS, University of Strasbourg CNRS
Resume : The creation of a photonic jet at the tip of an optical fibre is an upcoming trend with various applications. The propagative, slightly diverging, light beam coming out of the fibre does not behave in accordance to the usual laws of wave optics. For example, the diffraction limit can be overcome, giving a FWHM smaller than a half wavelength. These unusual properties make the photonic jet an excellent tool for subwavelength micromachining. The shaping of optical fibre tips is commonly done by thermoforming. Nevertheless, this method has some shortcomings for single mode fibers: the curvature of the tip is harder to control and the effect on the size and shape of the core and its concentration in dopant is unknown. This study investigates an alternative fabrication process to obtain the desired tip shape: chemical etching. The simulation of the shape of the photonic jet out of single mode fibres was made by 2D FEM modelisation. The fibres were isotropically etched in 24% HF. The chemical etching process was studied both statically and dynamically, along with the effect of the vapours. By carefully controlling the experimental conditions, shapes in close accordance to the theoretical predictions were obtained. The tip shapes were observed by optical microscope and the size of the photonic nanojets measured through laser ablation on Si. Eight time less energy has been required for etching using a single mode fiber tip shaped combining both chemical etching and thermoforming. Intro : Fibre tip shaping, HF, chemical etching, photonic nanojet
Laser interaction with matter: fundamentals and applications II : Esther Rebollar
Authors : Spencer D. Golze, Sergei Rouvimov, Robert D. Neal, Robert A. Hughes, Svetlana Neretina
Affiliations : College of Engineering, University of Notre Dame, IN 46556, United States Notre Dame Integrated Imaging Facility, University of Notre Dame, IN 46556, United States
Resume : Dr. Neretina’s laboratory has developed a new synthetic procedure for generating periodic arrays of metallic nanostructures shaped as hexagonal or triangular nanoplates using a room temperature light-activated growth mode. Such structures have the potential to act as the active components for the detection of biological and chemical analytes using various sensing modalities (e.g., Surface Enhanced Raman Scattering (SERS)). The synthesis is reliant on the formation of Au seeds exhibiting planar defects – without such defects the growth mode is deactivated. Through the engineering of defects, which have been extensively studied using Titan TEM imaging and electron diffraction, such structures have now been produced in high yield. Here, we will describe the techniques used to generate periodic array of seeds, demonstrate their utility in forming substrate-based metallic nanoplates and provide an understanding of the opportunities and challenges that lie ahead.
Authors : Jan Lancok, T. Zikmund, J. Bulir, E. Maresiova, E. Chernova, L. Volfova, J. Valenta
Affiliations : Department of Analyses of Functional Materials, Institute of Physics of AS CR, Na Slovance2, Prague, 18221, Czech Republic; Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague 2, 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 fabrication of metallic NPs in UHV conditions embedded in fluoride matrix prevent the oxidisation, which could degrade of plasmonic properties of NPs. In our work we demonstrated successfully fabrication of Ag, Al, Rh and Bi NPs embedded by CaF2 and Pr3+:CaF2 films fabricated by Pulsed Laser Deposition techniques (NPs) with auxiliary Electron Beam Evaporation (fluoride) at UHV conditions. The size of the NPs was controlled by the number of the laser pulses focused on the metallic target and varied between 5 and 20 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. Results were compared and discussed with the results of analysis structural properties performed by SEM, TEM, AFM and XRD. The calculated absorption cross absorption effective cross-section will be compared with experimental results. The plasmonic behaviour of metal NPs will be compared with those presented for metal oxides nanocomposites. The effect of NPs on luminescence and down conversion properties of Pr3+:CaF2 films will be presented as a function of their structural properties.
Authors : Tetsuo Tsuchiya, Yuko Uzawa, Tomohiko Nakajima, Muneyasu Suzuki, Iwao Yamaguchi
Affiliations : Advanced Coating Technology Research Center National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
Resume : Considering the recent global interest in reducing energy consumption, SiC power electronics technology is now ready to enable the step to the next plateau for efficiency standards. In most case, SiC power modules are designed to work at operating temperatures around 250 oC. Therefore, comical available electronic components such as resistor, cannot use for the SiC modules because the electrode and resistor materials is deterioration in the temperature. In addition, we found that the trimming part is not good for the heat cycling properties (-40-250oC). To overcome this problem, we developed new thin film resistor by using a photo reaction of hybrid solution (PRHS) process. In this presentation, we will explain the PRHS process for the flexible oxide thin film resistor, capacitor and its electrical properties. First of all, we have developed the new hybrid solution for the thin film resistor. The hybrid solution was prepared by mixing the Ru organic solution and RuO2 particles without any glass and an organic vehicle. The hybrid solution was spin-coated on the Al2O3 or polyimide substrate. The coated hybrid solution was heated or irradiated by UV lamp. The film was characterized by XRD, SEM and electrical measurements. Flexible RuO2 film was successfully prepared by PRHS process at room temperature. Resistivity of the flexible RuO2 film was 4.8×10-4Ωcm. The resistance change was 2.4% at the temperature range from 300 to 25oC. In addition, at the time of implementation, flexible resistor would be expected to relax the crack that comes from the difference in the thermal mechanical properties. In addition, by using PRHS, patterned resistor film was formed by UV irradiation using the photomask after leaching the solvents. So PRP process is effective for not only crystallization but also patterning. Detail results will be presented in the conference. This work was supported by Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), "Next-generation power electronics/Consistent R&D of next-generation SiC power electronics" (funding agency: NEDO)
Authors : Michel Meunier, Adrien Dagallier, Remi Lachaine, Christos Boutopoulos, Etienne Boulais
Affiliations : Polytechnique Montreal, Department of Engineering physics.
Resume : Irradiating plasmonic nanostructures with an ultrafast laser beam produces highly localized processes on the nanoscale in the surrounding medium. When these nanomaterials are imbedded in a biological media, their irradiation by a fs laser could results in a highly localized plasma, heat production and mechanical effects yielding to the production of nanobubbles and nanosurgery of cells. Recent developments of the fundamentals, modeling and applications of nanoplasmonics enhanced ultrafast laser nanosurgery of living cells will be presented. We will present a complete model that successfully describes all interactions occurring during the irradiation of plasmonics nanostructures by an ultrafast laser of various pulse widths and fluences. This model together with the help of the shadowgraphic imaging and scattering techniques, give valuable insight on the mechanisms of cavitation at the nanoscale, leading to the optimization of the nanostructure for bubble-based nanomedicine applications. We will also describe an in-silico rational design approach based on our theoretical modeling that optimizes cavitation without breaking the nanostructure. Using this framework, we demonstrate that nanoshells (NS) can significantly reduce the cavitation threshold in the near-infrared. Applications of laser optoporation and transfection of cells in various field of nanomedecine will be discussed. This technique has been successfully used to locally stimulate neurons.
Authors : Aida Naghilou , Jasmin Schubert , Oskar Armbruster , Leonid Zhigilei [1,2], Wolfgang Kautek 
Affiliations :  University of Vienna, Department of Physical Chemistry, Vienna, Austria;  University of Virginia, Department of Materials Science and Engineering, Charlottesville, Virginia, USA
Resume : Femtosecond ablation of metal thin films has been of vivid interest since decades [1,2]. Microbumps and nanojets have been observed on thin metal films [3-5]. The generation of microbumps has been attributed to two different mechanisms considering a loss of film strength without melting  and due to melting [3,4]. Metallic and non-metallic microbumps have the potential for various applications due to their unique properties such as wettability , superhydrophobicity  and self-cleaning . In this study, the generation of microbumps on single and stacked copper/silver double layers has been investigated. The microbumps were characterized by SEM and EDX. Two temperature model calculations were employed to clarify the dynamics of microbump generation.  W. Kautek and J. Krüger, Proceedings of SPIE 2207, 600 (1994).  J. Krüger and W. Kautek, Proceedings of SPIE 2403, 436 (1995).  A. I. Kuznetsov, C. Unger, J. Koch, and B. N. Chichkov, Applied Physics A 106, 479 (2012).  D. S. Ivanov, Z. Lin, B. Rethfeld, G. M. O’Connor, T. J. Glynn, and L. V. Zhigilei, Journal of Applied Physics 107, 013519 (2010).  Y. P. Meshcheryakov and N. M. Bulgakova, Applied Physics A 82, 363 (2006).  B. J. Basu, V. Hariprakash, S. T. Aruna, R. V. Lakshmi, J. Manasa, and B. S. Shruthi, Journal of Sol-Gel Science and Technology 56, 278 (2010).  K. Rajavel, R. Gomathi, R. Pandian, and R. T. R. Kumar, Inorganic and Nano-Metal Chemistry 47, 1196 (2017).  H. Yu, J. Liu, X. Fan, W. Yan, L. Han, J. Han, X. Zhang, T. Hong, and Z. Liu, Materials Chemistry and Physics 170, 52 (2016).
Laser interaction with matter: fundamentals and applications III : Svetlana Neretina
Authors : Thomas Winkler, Lasse Haahr-Lillevang, Cristian Sarpe, Bastian Zielinski, Nadine Götte, Arne Senftleben, Thomas Baumert, Peter Balling
Affiliations : Thomas Winkler; Cristian Sarpe; Bastian Zielinski; Nadine Götte; Arne Senftleben; Thomas Baumert; Institute of Physics and CINSaT, University of Kassel, Heinrich-Plett-Strasse 40, D-34132 Kassel, Germany. Lasse Haahr-Lillevang; Peter Balling; Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
Resume : When exposed to an ultrashort laser pulse, dielectric materials exhibit rapid changes in the optical properties induced by the strong-field excitation of electrons from the valence to the conduction band. The transient electron plasma can be seen experimentally in pump-probe experiments using, e.g., time-resolved reflectivity and spectral interferometry. The general trends, reflecting the increasing electron density, are captured by numerical simulations of the excitation process in a multiple-rate-equation model. However, for a thin sapphire sample, we recently observed the surprising occurrence of coherent optical amplification of a 400 nm probe pulse after excitation by an 800 nm pump pulse. The amplification factor depends non-linearly on the probe-pulse energy and is thus attributed to two-photon stimulated emission based on population inversion between the bottom of the conduction band and the top of the valence band. The gain occurs after a few hundred femtoseconds, consistent with a relaxation of the carriers to the band edge in combination with a carrier-induced band-gap shrinkage. The gain persists at pump-probe delays exceeding several tens of picoseconds [Nature Physics 14, 74?79 (2018); doi:10.1038/nphys4265].
Authors : Sergej Orlov, Ada Gajauskaitė, Pavel Gotovski, Vitalis Vosylius, Vytautas Jukna
Affiliations : State research institute Center for Physical Sciences and Technology, Industrial Laboratory for Photonic Technologies, Sauletekio ave 3, LT-10222, Vilnius, Lithuania
Resume : Focus wave modes (FWM) are solutions of scalar Helmholtz equation, which are localized and can ideally propagate long distances without spreading due to diffraction and dispersion. This type of pulsed beams is understood in terms of superposition of individual monochromatic Bessel beams with a given angular dispersion. Here, we extend the concept of FWM's to another two classes of nondiffracting beams - parabolic Weber-type and elliptic Mathieu beams. We aim to construct a scalar analogues to the classic FWM's and investigate their propagation inside a dielectric material, when their temporal durations can be up to few cycles. Furthermore, due to the large spatial angles introduced by the angular dispersion required for those durations, vectorial theory is introduced. We overcome this problem by introducing vector parabolic and elliptic nondifracting beams with controllable axial polarization, which can be either linear, circular and radial or azimuthal. Those newly obtained vector monochromatic beams are substituted into expressions for nondiffracting and nondispersive pulsed beams and, as a result, spatio-temporal distortions are successfully compensated. Lastly, we dive into problems arising while applying these vectorial pulsed beams for laser-microprocessing applications. Finally, we briefly report here on generation and implementation of the considered pulsed beams in scenarios involving a laser-micromachining of transparent dielectric materials.
Authors : Leïla Ben-Mahfoud ; Elena P. Silaeva ; Emile Bevillon ; Razvan Stoian ; Jean-Philippe Colombier
Affiliations : Univ Lyon, UJM-Saint-Etienne, CNRS, Institute of Optics Graduate School, Laboratoire Hubert Curien UMR5516, F-42023 St-Etienne, France
Resume : In the context of ultrashort laser-induced texturing of metals, the mechanisms involved in phase transformation determine the rapidity and the precision of the structuring process of the surface. The laser pulse produces an intense electronic excitation that transforms electronic and atomic structures to accommodate the energy of interaction between the electrons. A theoretical approach is proposed to predict the ultrafast processes on times shorter than electron-phonon dynamics, on the hundreds of femtosecond timescale. The lattice destabilization scenario is investigated theoretically from ab initio calculations relying on density functional theory (DFT) and time-dependent DFT simulations. First-principles calculations show that laser photo-excitation drives a charge distortion in the cold crystalline atomic arrangement. This induces high electronic stress and temperature along with an entropy increase on the subpicosecond timescale, with a potential for surface destructuring. In particular, electronic free energy dependence on interatomic distance as a function of the degree of ultrafast heating of metals establish nonequilibrium interatomic potentials revealing the disappearance of a free energy minimum. This shows that the electronic charge redistribution affects the lattice cohesion through non-thermal phenomena related to modified ion screening and high entropy effects.
Authors : Florin Jipa, Stefana Iosub, Bogdan Calin, Emanuel Axente, Felix Sima*, Koji Sugioka*
Affiliations : Center for Advanced Laser Technologies (CETAL), National Institute for Laser, Plasma and Radiation Physics (INFLPR), 409 Atomistilor, RO-77125 Magurele, Romania *RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
Resume : Microfluidic biochips represent controllable environment platforms, offering the possibility to investigate biological reactions at a microscale level including intra-cellular reaction and single-molecule detection. Unlike the polymer-based bio-chips, the miniaturized microfluidic platforms fabricated usually by NIR femtosecond lasers in photosensitive-glass has additional advantages such as strength for easy handling and chemical resistance. In this work we propose a new approach for the fabrication of embedded 3D structures in photosensitive glasses by high-repetition-rate picosecond laser processing. Different shapes of micro-channels and reservoirs, generally used in the bio-chips design, are achieved in volume of the glass by picosecond laser irradiation followed by thermal treatment and wet chemical etching. The obtained results have revealed that picosecond laser offers several advantage such as a reduced processing time for large areas and low fabrication cost.
Authors : A. Sikora, G. Coustillier, T. Sarnet, M. Sentis
Affiliations : Aix-Marseille University, CNRS, LP3, F-13288 Marseille, France
Resume : Engraving microstructures with highly smooth sidewalls is required for several applications. As examples, the roughness is a determinant factor to reduce liquid friction in microfluidic devices, to minimize scattering losses in ridge waveguides or to prepare clean cross sections for TEM and SEM analysis. Among elaboration techniques, ultrafast laser machining stands out from others by being contactless, maskless, fast and by minimizing thermal damage. As laser smoothing of sidewalls has been poorly reported in the literature, engraving have been studied with two picosecond lasers (8 and 50 ps) in silicon at atmospheric pressure by varying the laser wavelength (343 and 532 nm), the fluence and the beam scanning strategy, and characterized using SEM and confocal microscopy. This study shows that a fine tuning of the pulse overlap drastically enhances the smoothness of the flanks (less than 40 nm Ra). Moreover, it is found that laser engraving induces a structuration with a periodicity matching the pulse to pulse distance. The maximum profile height increases with this distance in accordance with a simple geometric model. Theoretically, less than 1 nm Ra should be obtained for pulse overlaps close to 100%. However, experiments show that the optimal surface quality is obtained at a much lower overlap (~80%) due to debris induced scattering on the edge. Acknowledgement: This work has been carried out in the frame of the European project SAM3 funded by EURIPIDES2 and CATRENE.
Laser interaction with matter: fundamentals and applications IV : Peter Balling
Authors : S. Maragkaki, E. L. Gurevich
Affiliations : Ruhr-University Bochum, Germany
Resume : Laser-induced periodic surface structures (LIPSS) or ripples appear on different solid surfaces upon exposure to ultrashort laser pulses. We generate ripples in different liquids such as in water, methanol and ethanol. In contrast to the experiments in air or in vacuum, the LIPSS formation in liquids is in competition with additional effects influencing the pattern formation. They are: bubble formation due to the liquid boiling, self-focusing and frequency conversion due to relatively high nonlinear refractive index of the environment. Experimental parameters, at which the influence of these additional factors is diminished, are analysed and uniform ripples are obtained. Change in the ripples orientation with the incident pulse fluence is observed and discussed.
Authors : A.Talbi, P. Coddet, V. Roge, M. Tabbal, E. Millon, A.L. Thomann, A. Stolz, C. Boulmer-Leborgne, GM. O'Connor, N. Semmar
Affiliations : GREMI-UMR 7344-CNRS-University of Orleans, 14 rue d’Issoudun, BP6744, 45071 Orleans Cedex2, France; Department of Physics, American University of Beirut, Bliss St., P.O. Box: 11-0236, Beirut, Lebanon 1107 2020; NCLA/Inspire Laboratories, School of Physics, National University of Ireland Galway, University Road, Galway, Ireland
Resume : Surface nanostructuring using ultrashort laser beams has been shown to improve the thermoelectric properties of thin films through the formation of laser induced periodic surfaces structures (LIPSS). A good control of the formation of such structures could induce a better confinement of phonons in the material leading to the reduction of the thermal conductivity without destroying the electrical and Seebeck coefficients. In this work, we perform a comparative study of LIPSS formation on stoichiometric and sub-stoichiometric titanium oxide thin films (TiO2 and TiOx, with 1.6 ≤ x ≤1.8) that were grown using two different techniques, namely pulsed laser deposition (PLD) and magnetron sputtering (MS). Irradiation was performed using two femtosecond laser beams, with pulse width of 100 and 500 fs and wavelengths 266 and 1030 nm respectively. Other laser irradiation parameters such as beam scanning speed and laser fluence were varied and conditions for the formation of LIPSS were determined for both types of films, as observed by Scanning Electron Microscopy (SEM). A variety of nanostructures were thus detected and their shapes and sizes were found to strongly depend on initial growth technique, whether PLD or MS. The difference in the LIPSS patterns between both sets of films can be correlated to difference in their initial morphology and nanostructure. The mechanisms of LIPSS formation were mainly attributed to free-surface energy minimization, involving several forces (surface tension, thermo-capillarity instabilities) that contributed to move, agglomerate and organize the material in regular structures. Finally, laser nano-structuring of large and homogeneous surfaces up to 25 x 25 mm² show significant improvement of the films’ thermoelectric properties, and more particularly a huge increase of the Seebeck coefficient leading to a noticeable enhancement of the ZT figure of merit.
Authors : E. H. Sánchez (1), G. Rodríguez (1), R. Caballero (1), J. M. Colino (1) P. Muñiz (2), P. S. Normile (2), J. A. de Toro (2) E. Rebollar (3), M. Castillejo (3)
Affiliations : (1) Instituto de Nanociencia, Nanotecnología y Materiales Moleculares, Universidad de Castilla-La Mancha, Campus de la Fábrica de Armas, 45071 Toledo, Spain (2) Instituto Regional Investigación Científica Aplicada, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain (3) Instituto de Química-Física Rocasolano, Consejo Superior de Investigaciones Científicas, Serrano 119, 28006 Madrid, Spain
Resume : Planar arrays of nanoribbons are made with Pd nanoparticles obliquely deposited on PET substrates previously processed for Laser Induced Patterned Surface Structures (LIPSS). This new materials system is here studied as a candidate for anisotropic and flexible transparent conductor (TC). LIPSS on PET thin foils are first patterned with a linearly polarized nanosecond 266 nm laser scanned all over the substrates . Dynamic mode Atomic Force Microscopy (topography and phase-contrast) is used to characterize the surface pattern. As-prepared specimens are comprised of large area, high coherence nanoripple pattern with a mean spacing 200 nm and average amplitude 46 nm. Separately, in a gas phase aggregation vacuum equipment, a beam of Pd nanoparticles (diameter 5 nm) is deposited on the LIPSS at an incidence angle 60-65º directed as to become partially shadowed by the ripple ridges. After the Pd deposition (estimate mean thickness 10 nm) the surface pattern preserves spacing and the phase-contrast AFM images show modulation across the ripples indicating formation of ribbons over the pattern. Optical transmittance in the visible and near UV range as well as four-probe electrical resistance measurements at room temperature are discussed and compared with requirements for next generation TC.  E. Rebollar, M. Castillejo, T. A. Ezquerra, “Laser Induced periodic surface structures on polymer films: From fundamentals to applications”. European Polymer Journal 73 (2015), 162-174
Authors : P. Pou(1), J.del Val(1,3), A. Riveiro(1), R.Comesaña(2), F. Arias-González(1), F. Lusquiños(1), M. Bountinguiza(1), F. Quintero(1), J.Pou(1,3)
Affiliations : (1) Applied Physics Dept., University of Vigo, EEI, Lagoas-Marcosende, Vigo, 36310 Spain. (2) Materials Engineering, Applied Mech. and Construction Dpt., University of Vigo, EEI, 36310 Vigo, Spain. (3) Department of Mechanical Engineering, Columbia University, New York, New York 10027, USA.
Resume : Defined as the tendency of a liquid to spread when in contact with a solid surface, wettability plays a major role in a variety of surface related phenomena as corrosion, heat transfer or tissue adhesion on implants. Consequently, great research effort is being devoted to address the wettability control of functional surfaces. Pulsed laser texturing at micro/nanometric level has been widely used for that purpose as a precision/time efficient technique. This work deals with the control of the wettability of AISI 304L stainless steel surfaces via laser texturing using three different pulsed laser sources working at the nanosecond regime. Samples wettability, measured via the contact angle θ (º), was systematically studied regarding to the processing parameters: wavelength, laser power, scanning speed, pulse frequency, track distance, and processing atmosphere. The exposure EX (J/mm2) has been identified as the key factor controlling the amount of change in θ (º), whereas the atmosphere has arisen as the one which drives that change towards more hydrophobic or hydrophilic values. The observed tendencies between wettability and the processing conditions have been related to the modifications in surface topography and chemistry induced by the laser treatment. Based on this knowledge, the processing parameters can be tuned to tailor the wettability of the untreated surfaces (θ = 88º) up to the desired value, ranging from superhydrophilicity (θ=0º) to superhydrophobicity (θ=152º).
Authors : F. Fraggelakis (1-2), G. Mincuzzi (1), J. Lopez (1-2), Inka Manek-Hönninger (2) and R. Kling (1)
Affiliations : (1) ALPhANOV, Technological Centre for Optics and Lasers, Optic Institute of Aquitaine, Rue F. Mitterrand 33400 Talence, France (2) Université de Bordeaux, CNRS, CEA, CELIA UMR5107, 33405 Talence, France
Resume : Laser induced periodic surface structures (LIPSS) has been emerged as a reliable technology to improve and control Key functionalities on solids surfaces. We mention for instance, modification of tribological properties and surface wettability as well as selective bacterial adhesion. Recently, novel morphologies such as rhombic or triangular periodic, sub µm, structures have been introduced, opening the possibility to exploit LIPSS in novel applications like anti-icing, bactericidal and antireflection. Interestingly, surface texturing with double femtosecond pulses is a reliable technology to generate morphologies with no linear symmetry. Nevertheless, a significant part of the results reported only refers to inhomogeneous structures generated over area as small as a spot size. Here we show for the first time that by using a delay line based set-up (inter-pulse delay Δt varying from -100 ps up to 2 ns) is possible to generate a variety of homogeneous structures over large area. Our setup exploits almost ~100% of the power of an industrial femtosecond laser with pulse duration of 350 fs emitting at 1030 nm and operating with repetition rates up to 1 MHz. The surface morphology was characterized by SEM and FT. We illustrate the effect of the interplay between the process parameters and Δt on the induced morphology. We believe that our results provide ground-breaking data on material surface processing providing effective solutions for high demand industrial applications.
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Materials Processing & Devices I : Maria Farsari
Authors : B. Poumellec, M. Lancry, J. Cao, J. Tian, F. Brisset
Affiliations : Université Paris-Sud
Resume : We study the structural modifications produced by irradiation of silica based glasses with femtosecond lasers. We have pointed out two new cases that are particularly interesting either from fundamental point of view that for the applications and showing the potential of this equipment in materials science: - Silica is an achiral glass. Nevertheless, for some values of the laser parameters and especially of its polarization direction versus the laser scanning, we can create rotatory power and circular dichroism. - The following glass 33Li2O-33Nb2O5-34SiO2 exhibits the potentiality to precipitate LiNbO3 crystals that are optically non-linear active (e.g. second harmonic generation), when the laser pulse repetition rate is above 100-200kHz. We have shown that when the crystal is nanosized, it is possible to orient them with the laser polarization. During the presentation, I will make a short review on published results on the two subjects. I will suggest mechanisms for the two findings that are quite different at first sight but both related to physico-chemical phase separation. The important fundamental aspect here is that light polarization appears to be a new “button” that we can adjust in solid phase in order to control and orient a transformation, in short the immaterial acts on the material. In the field of applications (integrated optics), the creation and control of the direction of the birefringence, of the circular properties and of the second order optical properties open unprecedented possibilities.
Authors : David M Roper; Stephen Ho; Moez Haque; Peter R Herman
Affiliations : University of Cambridge / University of Toronto; University of Toronto; University of Toronto; University of Toronto
Resume : Interferometric ultra-fast laser interactions within thin dielectric films provide an emerging tool to generate novel surface and intra-film structures through confinement of non-linear optical phenomena on nano-scale dimensions of /2n fringe maxima. This paper extends our prior demonstration of intra-film cleaving of SiOx and Si3N4 dielectric thin-films on silicon substrates to unveil an expansive range of new nano/micro-scale morphologies in SiOx film. The intra-film structuring is driven from a multi-level stack of thin (≈ 40 nm) plasma disks, formed by a single laser pulse. A planar stack of micro-explosions present complex ablation and shock front physics. Morphology evolves with increasing laser pulse energy from formation of single to stacked micro- and nano-cavities, leading to quantized /2n intra-film ejections, and formation of nano/micro-blisters having complex multi-layered intra-film modification. Sequential quantized blistering and ejections open into ultra-thin glass “balloons” with ≈ 100 nm SiOx walls and near-spherical geometry from deep intra-film zones. Alternatively, such spheres may burst to create previously unreported topographies, such as cylindrical walls perpendicular to the transparent film surface. At high exposure, cross-sectional SEM of ion-milled films unveil multi-layered and inter-nested micro-chambers, whereby deepest film segments undergo laser cleaving and fusion by competition from upper layer shock fronts. Laser interferometric processing thus offers novel film morphologies not found in conventional surface processing methods, opening new application directions for micro-device manufacture, CMOS compatible microelectronics, nano-photonics and surface topology attractive for cellular/biological study.
Authors : Maxime Chambonneau 1, Xinya Wang 2, Xiaoming Yu 2 3, Qingfeng Li 1, Nicolas Sanner 1, Shuting Lei 2, David Grojo 1
Affiliations : 1 Aix-Marseille University, CNRS, LP3 UMR 7341, Marseille, France 2 Department of Industrial and Manufacturing Systems Engineering, Kansas State University, Manhattan, USA 3 CREOL, The College of Optics and Photonics, University of Central Florida, Orlando
Resume : Although the first demonstrations on the functionalization of glasses with laser pulses were provided more than two decades ago, no comparable technique exists inside silicon so far. Recently, nanosecond infrared pulses were employed for achieving permanent bulk modifications. In this study, we expand on the interaction regime which recently allowed us to demonstrate the first laser inscription of waveguides in the bulk of monolithic crystalline silicon. The writing procedure relies on 5 ns duration infrared laser pulses, tightly focused deep inside the bulk of silicon and longitudinally moved with respect to the sample. An in situ infrared phase-shift microscope has been specifically developed for accessing the refractive index change Δn. Depending on the writing speed, the channels exhibit either micro-cavities or nearly homogeneously densified volume. In this latter case where Δn≈5.3×10^(-3), the injection of light inside the structures proves their light-guiding properties. The modifications also exhibit different chemical etching rates. Etching using KOH not only enables to machine the silicon samples, but also to reveal the channels written in the bulk at different speeds for detailed material analyses. These analyses provide paramount information on the material science involved in this emerging regime of laser-matter interaction. The whole study is of broad interest for numerous applications including the growing field of silicon photonics as well as microfluidics.
Materials Processing & Devices II : Bertrand Poumellec
Authors : M. Farsari
Affiliations : IESL-FORTH, N. Plastira 100, 70013, Heraklion, Crete, Greece. email@example.com
Resume : Multiphoton Lithography is a laser-based additive manufacturing technique which allows fabrication with resolution down to a few tens of nanometres. Based on nonlinear absorption, Multiphoton Lithography has unique capabilities that no-other technique can provide. It has been implemented with a variety of materials and several components and devices have been fabricated such as metamaterials, biomedical devices, photocatalytic systems and mechanical models The unique capability of Multiphoton Lithography lies in that it allows the fabrication of computer-designed, fully functional 3D devices. In this talk, I summarize the principles of microfabrication, and present recent research in materials processing and functionalization of 3D structures. Finally, I discuss future applications and prospects for the technology.
Authors : Søren H. Møller , Gunhild Thorsen , Adnan Nazir , Joakim Vester-Petersen , Emil H. Eriksen , Brian Julsgaard [1,3], Søren P. Madsen , and Peter Balling [1,3]
Affiliations : Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark ; Department of Engineering, Aarhus University, Inge Lehmanns Gade 10, DK-8000 Aarhus C, Denmark ; Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark 
Resume : The ability of plasmonic nanoparticles to greatly enhance the electric field of incident light in the near-field zone has many useful applications. One such application is enhancing upconversion of near-infrared light for improving solar cells . Careful design of the nanoparticle geometry by numerical optimization can potentially lead to much improved results . However, this approach requires, in particular, that the simulated near fields are very accurate. Electric near fields can be visualized experimentally by covering the nanoparticles with a polymer and subsequently polymerizing it with a laser in such a way that polymerization occurs only due to near-field enhancements . By combining scanning electron microscopy and atomic force microscopy, surfaces of constant near-field enhancement can be traced out in 3D. Here, we present our results of using this technique on designed nanoparticles for validating near-field simulations. Multi-photon polymerization is carried out with a tunable, femtosecond laser source. By changing the irradiation wavelength, the spectral response of the nanoparticle is obtained, providing a broader basis on which to compare the simulated and measured plasmonic near fields.  H. Lakhotiya et al., Appl. Phys. Lett. 109(26), 263102 (2016)  J. Vester-Petersen, Appl. Phys. Lett. 111, 133102 (2017)  T. Geldhauser, Langmuir 28(24), 9041 (2012)
Authors : A. Guarnaccio 1, A. Santagata 1*, F. Toschi 1, P. Dolce 1, D. Mollica 1, A. Bellucci 2, D. M. Trucchi 2, A. Lettino 3, L. Medici 3, and S. Orlando 1 *(corresponding author: firstname.lastname@example.org)
Affiliations : 1 CNR – ISM, Sede di Tito Scalo, Zona Industriale di Tito Scalo; 85100 (PZ), Italy 2 CNR – ISM, Sede di Montelibretti, Via Salaria Km 29,300; 00016 Montelibretti (RM), Italy 3 CNR – IMAA, Zona Industriale di Tito Scalo; 85100 (PZ), 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 environmental monitoring or products of common use in everyday life. Plasma and 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 several different plasma (RF, MW, and HF-CVD) and laser (ns Nd:YAG and Excimer, fs Ti:Sa and OPA) sources in order to evidence differences in the obtained results induced by photo-chemical, photo-physical, and photo-thermal processes. The main parameters investigated for plasma sources were: applied power and (reactive or inert) gas pressure. Instead for laser sources were: pulse energy, spot dimension, beam travel speed, vacuum and (reactive or inert) gas pressure. Plasma-treated and laser-irradiated samples were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurement. Morphological results indicated that ripple-like structures of micrometer and sub-micrometer size formed after the laser and plasma irradiation, respectively.
Authors : Klaus Zimmer1, Joachim Zajadacz1, Andre Mayer2, Christian Steinberg2, Hella-Christin Scheer2
Affiliations : 1 Leibniz Institute of Surface Engineering, Permoserstr. 15, D-04318 Leipzig, Germany; 2 Department of Electrical and Information Engineering, University of Wuppertal, Rainer-Gruenter-Str. 21, D-42119 Wuppertal, Germany
Resume : The nano patterning of surfaces and thin films with pattern dimensions of less than 50 nm is challenging, in particular for large-area, low-cost fabrication. However, self-assembly processes provide a mechanism of pattern generation in this dimensional range, enabling an alternative fabrication route to the traditional lithographic road. The current work focuses on laser heating for high-temperature short-time annealing of DiBCP films to achieve self-assembly into vertical lamellas with periods in the range of 50 nm. To get vertical lamellas of the DiBCP neutral substrate were coated with a ~60 nm thick DiBCP film by spin-coating which were irradiated thereafter with a scanned CO2-laser beam. Depending on the laser power and the scanning speed different degrees of self-assembly were achieved across the laser irradiated line. The experimental results on laser-induced local self-assembly are combined with thermal simulations to explain the laser induced thermal annealing at irradiation times below 0.1 s. Combining local heating by laser beams can provide a tool for direct writing of hierarchical nano-microscale patterns and also for dry development of self-assembled DiBCP at the same time.
Authors : Herbert Legall (1), Christoph Schwanke (1), Günter Dittmar (2), Jörn Bonse (1), Jörg Krüger (1)
Affiliations : (1) Bundesanstalt für Materialforschung und –prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany; (2) Steinbeis - Transferzentrum an der Hochschule Aalen, Albrecht-Erhardt-Str. 17, 73433 Aalen, Germany
Resume : Ultrashort laser pulse micromachining features a high precision. By increasing the repetition rate of the applied laser to several 100 kHz, laser processing becomes quick and cost-effective and make this method attractive for industrial applications. Upon exceeding a critical laser intensity, hard X-ray radiation is generated as a side effect. Even if the emitted X-ray dose per pulse is low, the accumulated X-ray dose becomes significant for high-repetition-rate laser systems so that radiation safety must be considered. The X-ray emission during ultrashort laser processing was investigated for different pulse durations and materials in an intensity range up to 1e15 W/cm2. The investigations were performed with two laser systems (925 fs, 1030 nm, 400 kHz, 40 W, Trumpf TruMicro 5000 and 30 fs, 800 nm, 1 kHz, 1 W, Femtolasers Compact Pro) e.g. on steel, wolfram, and glass in ambient air. Corresponding X-ray spectra and X-ray dose measurements are presented and the mechanism of X-ray generation will be discussed. By using a laser-intensity dependent scaling law, the emitted X-ray radiation for respective processing conditions can be predicted. The latter enables to implement suitable radiation protection strategies for various laser systems and processing parameters.
Poster session II : Wolfgang Kautek, Esther Rebollar, Daniele Pergolesi
Authors : Petr Hauschwitz, Danijela Rostohar, Petr Gavrilov, Tomas Mocek
Affiliations : HiLASE Centre, Institute of Physics ASCR, Za Radnici 828, 25241 Dolni Brezany, Czech Republic, Europe; Faculty of Nuclear Science and Physical Engineering, Czech Technical University, Brehova 7, 11519 Prague, Czech Republic, Europe; Laser Micro/Nano Fabrication Laboratory, Gwangju Institute of Science and Technolgy, 123 Cheomdan-gwagio, Buk-gu , Gwangju 500-712 Republic of Korea
Resume : Carbon fibre reinforced plastic (CFRP) is strong, lightweight and durable material with good corrosion and vibration resistance. It is a good candidate to replace metals in production of many parts, while an optimally designed CFRP part can be up to 70% lighter than steel and 30% lighter than aluminium as well as to have twice the strength, more than twice the fatigue resistance of steel and be twice time stiffer than aluminium. The benefit of CFRP for lightweight construction in automotive and airplane industries is widely accepted. Conventionally used techniques, such as shape-cutting and water-jet are connected with limitation related to quality and productivity. Therefore, laser processing, as a non-contact, flexible and easy to automated, was recently recognized as possible solution for large-volume production of CFRP parts. Unfortunately, this technology is also connected with two major chalanges: to machine the CFRP material with high speed and at the same time to minimize heat affected zone (HAZ). In this paper will be presented work on selecting processing strategies for two CFRP materials (C-PPS and C-PEEK) for various laser systems emitting in nIR and UV with pulse durations from ns to fs. Comparison of processing parameters (scanning speed, spot diameter, spot overlap) and laser parameters (pulse energy, repetition rate, pulse duration, wavelength) with respect to HAZ and cut quality for all processing strategies and optimal processing window for each laser system will be also presented.
Authors : Alberto Ramil (1), Ana J. López (1), Javier Lamas (1), Santiago Pozo-Antonio (2), Teresa Rivas (2)
Affiliations : (1) Centro de Investigacións Tecnolóxicas. Escola Politécnica Superior. Universidade da Coruña. Campus de Ferrol, 15471, Ferrol, Spain (2) Departamento de Enxeñaría dos Recursos Naturais e Medio Ambiente. Universidade de Vigo, Campus Lagoas-Marcosende, 36310, Vigo, Spain
Resume : Laser cleaning is a well stablished technique in different fields, among them conservation of Cultural Heritage. Currently laser cleaning systems are based on movement of the processing beam, or the workpiece positioning system, in two mutually perpendicular axes. Such systems are capable of cleaning flat (2D) surfaces placed perpendicularly to the processing beam. Our approach to process 3D surfaces is based on the prior knowledge of the workpiece surface by laser-triangulation profilometry. Using custom software, the profile data is transformed into a 3D model of the surface. From this model, the area to be cleaned is selected, as well as the laser processing parameters, i.e.; scanning speed, filling pattern and position of the beam focus in order to ensure an even cleaning treatment. Taking these parameters into account, the appropriate laser trajectories are calculated and, finally, orders are automatically generated for the controller of the sample positioning system. The results of the removal of paint from a granitic 3D stonework using the third harmonic of a Nd:YVO4 nanosecond laser are presented. Different analytical techniques used to evaluate the quality of the cleaning and possible damages in the stone surface confirmed the capacity of our system for the adequate laser processing of 3D surfaces. ACKNOWLEDGEMENTS This work was supported by BIA2014-54186-R Project; (Spanish Government, Ministry of Economy and Competitiveness). J.S. Pozo-Antonio was supported by a postdoctoral contract with the University of Vigo within the framework of the 2011–2015 Galician Plan for Research, Innovation and Growth (Plan I2C) for 2014.
Authors : Johannes B. Bergmann, Dafni Moatsou, Ullrich Steiner
Affiliations : Adolphe Merkle Institute University of Fribourg Chemin des Verdiers 4 CH-1700 Fribourg
Resume : As the development of biocompatible and/or biodegradable devices, such as implants and drug delivery systems, is constantly progressing, a wide range of bio-based and bio-inspired materials are becoming available. Further progress also requires the development of new methods focusing on the ease of preparation and processing. Microfluidic devices offer great opportunities in this context as a well-designed setup enabling the miniaturization of biological experiments by reducing the reagent volumes, shortening reaction times, and allowing for simultaneous complex operations by integrating laboratory protocols into a single chip device.1 In this work, we developed a straightforward 3D-printed microfluidic system that allows the preparation of microcapsules of uniform sizes through the formation of double emulsions. The presented system overcomes common limitations of microfluidic devices, such as high cost and lengthy procedures, while maintaining their reliability in producing microcapsules with interesting properties. Indeed, the successful formation of ethyl cellulose microcapsules is shown, while their potential applications in biological systems is discussed. 1. Dixit, C. K. & Kaushik, A. Microfuidics for Biologists. (2016).
Authors : P.A. Atanasov*1, N.N. Nedyalkov1, Ru. Nikov1, N. Fukata2, D. Hirsch3, B. Rauschenbach3
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 3Leibniz Institute of Surface Modification (IOM), Permoserstrasse 15, D-04318 Leipzig, Germany
Resume : This study deals with the use of laser techniques for preparation of advanced Au and Ag nanostructures on SiO2 (001) substrates to be applied for high-resolution analyses, namely, surface enhanced Raman spectroscopy (SERS) analyses. The activity was tested of the structures fabricated as substrates for SERS covered by small quantities (usually applied in agricultural medicine) of the fungicide Dithane DG (mancozeb). The study has a direct bearing on the human health and food quality by the way of assisting the detection of small amounts or residue of harmful pollutants.
Authors : M. Filipescu, A. Palla Papavlu, S. Bajnicov, V. Ion, M. Dinescu
Affiliations : National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor St, RO-077125, Magurele, Romania
Resume : Permanent, rigorous and efficient monitoring of the environmental pollution involves the use of efficient devices, namely sensors. The most important part of such a sensor is the active membrane that detects pollutants, based on chemical or physical phenomena. In the case of chemoresistive sensors, the use of new composite material by mixing organic and inorganic compounds appears to be a promising alternative. The aim of this work is to demonstrate the advantage of using nanostructured composites (WO3/polymer) as highly sensitive membranes to toxic gases, working also at low temperature. Matrix assisted pulsed laser evaporation was used to obtain these composites as thin films. The surface morphology was in detail studied by atomic force microscopy and scanning electron microscopy and the chemical structure was investigated by Fourier transformed infrared spectroscopy. The polymer/ WO3 ratio influence on the electrical properties was also evidenced. Acknowledgement: Financial support from the Romanian National Nucleu Program is gratefully acknowledged.
Authors : Jaemin Jung, Junghyo Nah, Min Hyung Lee
Affiliations : Department of Applied Chemistry, Kyung Hee University, Yongin, Gyeonggi 17104, Korea; Department of Electrical Engineering, Chungnam National University, Daejeon 34134, Korea.; Department of Applied Chemistry, Kyung Hee University, Yongin, Gyeonggi 17104, Korea
Resume : Design trend of electronic devices have been moved on smaller, thinner, lighter, and flexible and this trend will be pushed further to realize wearable and internet-on-thing devices. To keep pace with the flow in the electronics, micro-energy storage devices with high capacity and fast charge/discharge rate should be developed. Interdigitated microsupercapacitor (MSC) takes high potential for the micro power source due to its fast charge/discharge processes, long cycle life, and high power density compared to the microbatteries; however, fabrication of MSC with interdigitated electrodes selectively decorated with pseudo-capacitive materials such as transition metal oxides for increased capacitance are still challenging. Here, we developed simple fabrication of MSCs by in-situ formation of interdigitated graphene electrodes and ZnO nanorods by photothermal conversion of graphene oxides (GO) and Zn precursors using IR-laser scribing.
Authors : Alexandra Palla-Papavlu1, Stefan Voicu2, Horia Iovu3, Sorin Vizireanu1, Gheorghe Dinescu1, Maria Dinescu1
Affiliations : 1 National Institute for Lasers, Plasma, and Radiation Physics, Magurele, ZIP 077125, Romania 2 Faculty of Applied Chemistry and Materials Sciences, University Politehnica of Bucharest, Gh Polizu 1-7, 011061, Bucharest, Romania 3 Advanced Polymer Materials Group, University Politehnica of Bucharest, Gh. Polizu 1-7, Bucharest 011061, Romania
Resume : This work deals with the design, fabrication, and characterization of a fully integrated explosives detection platform based on a chemiresistive sensor array fabricated by laser-based methods. This detection platform is used for the detection of improvised explosives, as they are actually fabricated by terrorists due to the ease of access to unrestricted starting. The sensor array is fabricated by laser-induced forward transfer (LIFT) of nanomaterials, i.e. carbon nanotubes and hybrid carbon nanotubes decorated with semiconducting polymers. Conventional LIFT consists of the irradiation, using a pulsed laser, of a thin layer of an absorbing material (the donor) that has been deposited onto a transparent substrate. The layer is irradiated through the substrate and the light-matter interaction which takes place at the interface generates a strong increase of the local pressure. As a result, a small piece of the thin film located above the irradiated area is ejected (as a pixel) from the substrate surface and deposited onto a target substrate (the receiver) arranged in close proximity to the donor substrate. The size of the ejected material is controlled by the size of the incident laser spot. This work aims at 2 specific objectives: (1) The design and development of the integrated explosives detection platform, including explosives sensors / sensor arrays based on conductive polymers and single walled carbon nanotubes. (2) System integration, testing, and validation of integrated explosives detection platform. This corresponds to the development of a fully operational explosives detection system, able to perform sensitive and selective detection of the explosives of interest and consequently, a state of the art development in terms of sensors. Acknowledgement Financial support from i) NILPRP through the NUCLEU program and ii) UEFISCDI, though the “Fabrication, calibration, and testing of advanced integrated sensor systems aiming at applications in societal security (TESTES)” project are gratefully acknowledged.
Authors : Harim Oh, Jeeyoung Lee, Minseok Seo, Yoonseok Oh, Jaeyong Kim, Seonwoo Lee, Myeongkyu Lee
Affiliations : Yonsei University
Resume : Metal nanostructures have attracted a great deal of attention due to their unique properties and functionalities. In particular, noble metals at the nanometer scales exhibit distinct localized surface plasmon resonance (LSPR). The LSPR phenomenon can be effectively utilized for bio-sensors and noble optical devices such as color filters, polarizers and color printing. Although the spectral positions of LSPR peaks somewhat vary with particle size, the plasmonic behavior of these nanoparticles has a limited tuning range. Since Ag and Au particles exhibit resonance at different wavelengths, bimetallic particles will have a wider tuning range than the single-element paricles. We here show that bimetallic Ag-Au nanoparticles can be synthesized by irradiating commercial Ag nanowires coated with a thin Au film by a pulsed laser beam. This process is fundamentally based on Rayleigh instability. By adjusting the relative amounts of the two elements, we were able to tune the resonances peaks from 450 to 550 nm. More importantly, we could produce a few different plasmonic colors from a single sample simply by controlling the laser irradiance. This finding provides a possible way of implementing color laser printing without the need of using a pre-patterned template.
Authors : N.Nedyalkov1, M.E. Koleva1, N.E. Stankova1, R. Nikov1, P. Atanasov1, E. Yordanova2, G. Yankov2, L. Aleksandrov3, R. Iordanova3
Affiliations : 1Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784, Bulgaria, 2Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784, Bulgaria, 3Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. Georgi Bonchev str. bld.11, 1113 Sofia, Bulgaria
Resume : This work represents the response of noble metal composed borosilicate glass to laser radiation with femto- and nanosecond pulse duration. The sample material is gold or silver ion-doped borosilicate glass obtained by conventional melt quenching method. The produced glass samples are irradiated by laser pulses with femtosecond and nanosecond duration. The nature of the glass modifications as a function of the laser processing parameters is studied. For this purpose the laser fluence, laser wavelength and pulse number are varied in a wide range. Below the permanent modification threshold, defects associated with formation of color centers in the material are observed when femtosecond laser pulses are applied. The effect can be achieved for different wavelengths – in ultraviolet, visible and infrared spectral range. Irradiation with nanosecond laser pulses may also induce color change of the glass, but only at wavelength in the ultraviolet range. At conditions for permanent morphology modifications, different micro- and nanostructures are observed depending on the laser processing conditions. The annealing of the samples may result in formation of noble metal nanoparticles in the laser processed areas. Thus, the results can be used for fabrication of 3D complex composite systems in transparent materials that can be applied in the design of new optical components and lab on a chip devices.
Authors : N.Nedyalkov1, M.E. Koleva1, R. Nikov1, N.E. Stankova1, E. Yordanova2, G. Yankov2, L. Aleksandrov3, R. Iordanova3
Affiliations : 1Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784, Bulgaria, 2Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784, Bulgaria, 3Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. Georgi Bonchev str. bld.11, 1113 Sofia, Bulgaria
Resume : Noble metal nanoparticle composed glasses attract significant attention due to the unique optical properties that they express in the near UV and visible spectral range. These are related to the high values of the extinction cross section and nonlinear optical characteristics. In this work we study the ability of laser induced modification of the optical properties of borosilicate glasses that contain gold and silver nanoparticles. The process is investigated by application of laser pulses with femtosecond and nanosecond duration. It is shown that at certain conditions the glass optical properties can be modified as a change of the nanoparticles plasmon resonance wavelength is observed. The influence of the laser fluence, laser wavelength and pulse number on this effect is studied. A theoretical model based on multiparticle Mie scattering theory is applied to explain the observed modifications. On its basis and performed analyses can be concluded that the induced optical properties variations are related to modification of the nanoparticles size and shape. The obtained results indicate an ability of nanoparticle size and shape modifications with a high spatial resolution in 3D and can be used for fabrication of integrated optical systems.
Authors : D. Sola1, S. Alamri2, A.F. Lasagni2,3, P. Artal1
Affiliations : 1Laboratorio de Óptica, Centro de Investigación en Óptica y Nanofísica Universidad de Murcia Campus Espinardo, 30.100 Murcia, Spain 2Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS Winterbergstr. 28, 01277 Dresden, Germany 3Institut für Fertigungstechnik, Technische Universität Dresden Zeunerbau, George-Bähr-Str. 3c, 01062 Dresden, Germany
Resume : The fabrication of diffractive elements in ophthalmic polymers to induce refractive index changes is of great interest in the field of Optics and Ophthalmology for refractive correction. In this work, hydroxyethyl methacrylate and silicon-hydrogel contact lenses were structured with linear periodic patterns by means of Direct Laser Interference Patterning (DLIP). As laser sources, Q-switched laser systems emitting 10 ns pulses at a wavelength of 266 nm were used to produce periodic patterns on the surface of the polymer materials. The experiments were carried out employing a two-beam interference setup, studying the features of the laser processed areas as a function of both the laser fluence and the interference period. The topography of the structured areas was investigated using optical confocal microscopy. Compositional and structural modifications on the materials were studied by means of micro-Raman spectroscopy. Finally, periodic patterns were characterized through diffractive techniques to determine the diffractive properties of the DLIP periodic patterns.
Authors : Edgar Gutiérrez1, Álvaro Rodríguez-Rodríguez1, Mari Cruz García-Gutiérrez1, Aurora Nogales1, Tiberio A. Ezquerra1, Esther Rebollar2
Affiliations : 1Instituto de Estructura de la Materia (IEM-CSIC), Serrano 121, 28006 Madrid, Spain; 2Instituto de Química Física Rocasolano (IQFR-CSIC), Serrano 119, 28006 Madrid, Spain
Resume : Organic materials such as semiconducting polymers and fullerene derivatives have attracted much attention due to their potential applications in optics, electronics and photovoltaics among others. Nanostructuring by laser of semiconducting polymers has been recently accomplished rendering to functional surfaces of selective electrical conductivity, while micron size patterning by light of fullerene materials has been also described. However, at nanometer scale, ordering of fullerenes typically implies bottom-up strategies involving a template surface. Here, we report a one-step top-down laser-induced method to prepare [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) resist-free laser induced periodic surface structures (LIPSS) by illumination of spin-coated films with the second harmonic of a Nd:YAG laser. LIPSS selectively preserve the initial electrical conductivity of the PC71BM spin-coated films on the LIPSS valleys. The nanostructured sample can be solvent washed leaving in the laser illuminated zone an undissolved residue consisting of nanowires which were shown to be partially electrically conducting. It is proposed that laser irradiation induces an increase in the crystallinity of the bottom part of the hills and consequently enhances the electrical conductivity levels. These results point towards the potential use of the described technology for nanofabrication of organic electronic devices.
Authors : Claudiu Fleaca1, Florian Dumitrache1, Claudiu Locovei 2, Ana-Maria Banici1, Anca Badoi; Alina Ilie1 and 2, Stefan Banita1, Eugenia Vasile3, Ladislau Vekas4
Affiliations : 1: NILPRP, Atomistilor409, Magurele Bucharest, Romania 2: University of Bucharest, Atomistilor 405, Magurele Bucharest, Romania 3: Department of Oxide Materials and Nanomaterials, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Gh. Polizu 1‑7, Bucharest, Romania 4: Romanian Academy, Timisoara Branch, Mihai Viteazul blv. 24, Timisoara, Romania
Resume : Laser pyrolysis technique was employed for the synthesis of three different magnetic iron-based nanopowders starting from Fe(CO)5 vapors and C2H4 sensitizer mixture. Iron oxide maghemite particles were obtained in the supplementary presence of oxygen, whereas Fe metal/carbide@C nanoparticles were prepared using an additional C2H4 coaxial flow. Fe-Si magnetic nanoparticles were also synthesized by adding a separate nearby parallel SiH4 flow. These nanopowders were dispersed in aqueous solutions (using also hydrophilic agents for the case of those Fe-C type with hydrophobic surface) containing mixtures of water-soluble acrylate monomers: acrylic acid, acrylamide, N-isopropylacrylamide, 2-hydroxyethylmethacrylate and/or poly(ethyleneglycol) methacrylate in the presence of small amounts of N, N’ methylenebisacrylamide and APS (NH4)2S2O8. The resulted suspensions were subsequently gelled under bath ultrasonication at 70°C. The composite hydrogels were characterized by XRD, FT-IR, Raman, SEM and their magnetic properties were recorded. Their swelling behavior was also tested, as well as their capacity for heat release under alternative magnetic field for local hyperthermia applications.
Authors : Daeho Kim
Affiliations : Nano Hybrid Technology Research Center, Korea Electrotechnology Research Institute, Changwon-city, KOREA
Resume : High temperare thermal treatment is a fundamental method to enhance the crystallinity of materials or to recover its instrinsic properties after processes. However, the thermal treatments has become an inacceceble technic since the treatment temperature is usually limited by such as transparent or flexible subtrates. Here, it is introduced the microwave ‘induction’ heating as a selective and fast heating method for conductive thin film. In different with the conventional microwave dielectric heating for electrically polarized molocules, the microwave induction heating has mechanism that strong current induced by oscillating magnetic field in giga-hertz frequency generates ohmic heat in conduction thin film. A 20nm-thick silver thin film sputtered on 5mm-thick glass substrate for low thermal emissivity coating has been selectively heated more than 550oC in 300ms without thermal damage by the microwave induction heating, while the temperature of glass substrate is maintained around room temperature. The surface resistance of the silver thin film is reduced to near 30% due to crystallinity enhancement.
Authors : Regiane C. de Oliveira 1, Sonia M. Zanetti 2, Marcelo Assis 1, Maya Penha 1, Mayara Mondego 1, Mario Cilense 2, Elson Longo 2, Laecio S. Cavalcante 3
Affiliations : 1INCTMN-CDMF, Universidade Federal de São Carlos, São Carlos, SP, Brazil 2INCTMN-UNESP, Universidade Estadual Paulista, Araraquara, SP, Brazil 3PPGQ-CCN-DQ, Universidade Estadual do Piauí, Teresina, PI, Brazil
Resume : Recently, our group discovered a unwanted real-time in situ nucleation and growth processes of metallic Ag nanoparticles on different silver-based semiconductors, such as: α-Ag2WO4, β-Ag2MoO4, Ag3PO4 and β-AgVO3, which were driven by accelerated electron beam irradiation from an electron microscope under high vacuum. Now, we present new data on effect of grow of the metallic Ag nanoparticles (NPs) on the surface and electrical properties of the 3D flower-like Ag4V2O7 crystals. The crystals were obtained by coprecipitation method and was structurally characterized by X-ray diffraction patterns, which were well indexed to the orthorhombic structure. The Ag4V2O7 crystals exhibit a uniform shape as 3D flower-like, with average diameter of 4.3 µm. By the slicing of the flower-like crystals, it was observed internal pores and channels. To verify the growth of metallic Ag NPs on Ag4V2O7 crystal surface, an EDXS (Energy-dispersive X-ray spectroscopy) spectrum system coupled with a transmission electron microscopy (TEM) was used for analyzing. After 2 minutes under electron beam irradiation, silver growth on the Ag4V2O7 surface. As expected, EDXS results confirmed that the electrons beam promoted the random growth of the metallic Ag NPs. To evaluate the effect of growth of metallic Ag NPs on the electrical resistance of the 3D flower-like Ag4V2O7, the electrical measurements were evaluated with the exposure time to eletron beam, so with the growth of these metallic Ag NPs. Initially, the resistance is governed by the bulk properties. After 5 min irradiation a slight increase in resistance is observed, which can be attributed to formation of silver vacancy (V'Ag) in the semiconductor bulk, since, the clusters of [AgOx] interact with the incoming electrons, resulting in Ag reduction and the migration of the Ag from the bulk to the surface and the formation V'Ag. The negative vacancies (V'Ag) along with the oxygen vacancies (V●O), previously present, make the semiconductor more resistive for irradiation times until 20 min. However, after 40 min irradiation, it is observed a decrease in resistance, due to the formation of a layer of metallic silver in the semiconductor surface. From this point on, bulk and surface contribute equally to semiconductor resistance. After 60 min irradiation, a huge decrease in the resistance is observed, due to high density of metallic Ag nanoparticles on Ag4V2O7 crystals surface, which makes the bulk highly resistive. However, in this case, the resistance measurement is governed by the metallic surface which presents lower resistance. In summary, we have observed, for the first time, that the external electron beam irradiation, by MET induces the formation and growth of metallic Ag NPs on the 3D flower-like Ag4V2O7 crystals surface. Therefore, the irradiation generated Ag NPs two important advantages are obtained: generation of Ag NPs in the crystal surface and control of semiconductor properties by electron irradiation
Authors : M. Nistor 1, E. Millon 2, C. Cachoncinlle 2, J. Perrière 3,4
Affiliations : 1 National Institute for Lasers, Plasma and Radiation Physics (NILPRP), L22, PO Box. MG-36, 77125 Bucharest-Magurele, Romania; 2 GREMI, UMR 7344 CNRS-Université d’Orléans, 45067 Orléans Cedex 2, France; 3 Sorbonne Universités, UPMC Univ Paris 06, UMR 7588, INSP, F-75005, Paris, France ; 4 CNRS, UMR 7588, INSP, F-75005, Paris, France;
Resume : ZnO is one of the most investigated n-type semiconductor as transparent electrode for thin film solar cells and optoelectronic devices but the role of doping on the electrical and optical properties is not well understood. Here we report on the growth of Nd doped ZnO thin films by either pulsed laser deposition (PLD) or pulsed electron beam deposition (PED) on c-cut single crystal substrates at different substrate temperatures and gas pressures in an attempt to find the optimum doping concentration for minimal electrical resistivity. Although a structural disorder is induced by few % of Nd in the wurtzite ZnO network, epitaxial thin films are obtained even at relatively low substrate temperatures (300°C). Whatever the growth method, in-plane epitaxial relationships are observed and explained by the domain matching epitaxy model that matches integral multiples of planes across the film/surface interface. The doping is evidenced in both carrier concentration and structural disorder of the ZnO films leading to various optical and electrical film properties. The degenerate or non-degenerate semiconductor electrical properties of Nd:ZnO thin films are discussed in correlation with the strong influence of the growth conditions on the optical film properties in PLD and PED. This work demonstrates that Nd:ZnO thin films are promising transparent conductive oxides or optically active layers for photonic conversion in photovoltaic applications.
Authors : N. Scarisoareanu1, S. Brajnicov1,2, C. Viespe1, V. Dinca1, T. Constantin3, A. Palla Papavlu1 and M.Dinescu1
Affiliations : 1Lasers, National Institute for Lasers, Plasma and Radiation Physics, Bucharest, Romania 2 University of Craiova, Romania 3CMRC, Bucharest, Romania 4 University of Bucharest -Faculty of Physics, Bucharest, Romania
Resume : In the last decades, the organophosphate compounds have risen significant threatens and strains on environmental safety as well as on public health and homeland security. Within this context, the development of sensitive chemical sensors for the detection and measurements of contaminants is of high interest. In this work, we report on a laser method (i.e. Matrix assisted pulsed Laser Evaporation-MAPLE) for depositing an active polymeric based membrane for obtaining chemical sensors to be used for the analysis of organophosphate compounds. The deposition process of the polymer was carried out using an Nd:YAG pulsed laser, operating at different fluences (0.2–0.8 J/cm2 ) with a wavelength of 266 nm and a repetition rate of 10 Hz. It was found that for specific range of fluences 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. However, there were significant changes depending on the deposition parameters in morphologies revealed by Atomic Force Microscopy and Scanning Electron Microscopy. The surface acoustic wave sensors have been tested using the Network Analyzer before and after polymer deposition. The polymer coated surface acoustic wave sensors responses have been measured upon exposure to various concentrations of organophosphate analyte. All sensors coated showed a clear response to the tested vapor. The materials deposited by MAPLE provided good premises for the development of a sensor with suitable stability, good reproducibility, and high sensitivity towards samples. Our results indicate that the sensor system can be used as a rapid, simple alternative in the analyses of organophosphate compounds. Acknowledgments: This work was supported by Romanian National Authority for Scientific Research (CNCS–UEFISCDI), under the projects PED 214 and Nucleus programme..
Authors : N. Tarasenka1, A. Butsen1, A. Nevar1, N. Tarasenko1, E. Stankevičius2, P. Gečys2, R. Trusovas2, E. Daugnoraitė2, G.Račiukaitis2
Affiliations : 1B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus 2Center for Physical Sciences and Technology, Savanoriu Ave. 231, 02300 Vilnius, Lithuania
Resume : Silicon nanocrystals (SiNCs), or silicon quantum dots, defined as Si nanostructures with typical diameters below 10 nm, have recently attracted much attention due to a unique combination of their size-dependent optoelectronic properties and biocompatibility, which have great potential for use in biological imaging and diagnostic applications. In this work, we have developed and tested two laser-assisted approaches for controlled Si NCs synthesis: first is based on pulsed laser ablation of silicon in liquids, second – spark discharge between Si electrodes in liquid followed by laser irradiation of the formed colloid. Both approaches provide a possibility of synthesis control over the process and avoid use of reducing agents or chemical precursors. The focused beam of a Nd:YAG laser (1064 nm, 10 ns pulse width, 10 Hz repetition frequency) was used for ablation of Si target in distilled water, DMSO and 0.008 M aqueous DTPA solution. The phase composition, morphology, structure and optical properties of the synthesized nanoparticles have been investigated. The prepared ultrafine and well-dispersed SiNCs with an average diameter of about 5 nm exhibited blue luminescent emissions in the spectral range of 410-550 nm when excited at wavelengths near the direct band gap of the SiNCs. The luminescent emission band shifts to longer wavelengths with excitation wavelength increase. In the presentation, the potential of the prepared SiNCs for bio-imaging applications will be demonstrated.
Authors : Maria Massaouti1, Marianneza Chatzipetrou1, Marina Makrygianni1, George Tsekenis2, Ioanna Zergioti1
Affiliations : 1)Department of Applied Physics, National Technical University of Athens, Athens, 15780, Greece; 2)Biomedical Research Foundation of the Academy of Athens, Soranou Ephessiou 4, 11527 Athens, Greece
Resume : Hydrogels have recently received considerable attention as smart materials in the fabrication of various biosensors, due to their unique properties which can be customized to the suit the needs of each individual application. Further to this, the shift to a 3D surface geometry increases their loading capacity and better preserves the protein function due to the hydrophilic environment in comparison to conventional 2D functionalization techniques. To date, various microfabrication techniques have been employed for fabricating micropatterns of protein-incorporating hydrogels on surfaces such as robot-controlled, pin-based, inkjet printing and photolithography. Herein, an elegant approach based on the use of the Laser Induced Forward Transfer (LIFT) as a laser direct-write printing technique for creating micropatterns of functional hydrogel networks onto receiving surfaces in a spatially controlled and contactless manner, where no masks or time-consuming procedures are required, is presented. The technique has been employed for transferring and photo-polymerizing acrylate monomers into hydrogel networks onto silane-modified silicon based surfaces. The proteins (antibodies) were either incorporated into the prepolymer solution or bound to the hydrogels upon their polymerization. More specifically, antibodies were covalently immobilized into the hydrogels with the use of NHS-acrylate, while the porosity or the hydrogel was adjusted by varying the ratios of the following three monomers: 2-hydroxyethyl acrylate, poly (ethylene glycol) diacrylate and trimethylolpropane triacrylate. The antibody loading efficiency and their ability to recognize and bind to their antigen has been evaluated for prepolymer solutions of different compositions (monomer functionalities and ratios in the mixture) as well as laser printing conditions and compared to both hydrogels that have been drop casted and then either photopolymerized or chemically polymerized.
Authors : Laurentiu Rusen1, Madalina Icriverzi2,3, Valentina Dinca1, Livia Elena Sima2, Anca Bonciu1,4, Simona Brajnicov1,5, Nicoleta Dumitrescu1,5, Antoniu Modovan1, Anisoara Cimpean3, Anca Roseanu2 and Maria Dinescu1
Affiliations : 1 National Institute for Lasers, Plasma and Radiation Physics, Atomistilor 409, 077125, Magurele, Bucharest, Romania 2 Institute of Biochemistry, Romanian Academy, 296 Splaiul Independentei, Bucharest, Romania 3 University of Bucharest, Faculty of Biology, Department of Biochemistry and Molecular Biology, Bucharest Splaiul Independentei 90-94, Romania 4 University of Bucharest, Faculty of Physics, RO–077125, Magurele, Romania 5 University of Craiova, Faculty of Mathematics and Natural Sciences, RO-200585, Craiova, Romania
Resume : Smart biointerfaces have played an important role in tissue enginnering or biomedical related areas and were based on the correlation between the chemical and morphological characteristics and the biological response. In this work, Matrix-Assisted Pulsed Laser Evaporation (MAPLE) was used to obtain poly(N-isopropylacrylamide) (pNIPAM) and pNIPAM derivative based functional and thermo-responsive thin films. The morphology, roughness and hydrophobic/hydrophilic character, and the thermoresponsive response were investigated by atomic force microscopy and contact angle measurements under two temperature conditions. The change in the contact angle and thickness values when the temperature was shifted from 37°C to 24°C for all the materials tested demonstrated clearly the thermoresponse of the laser processed coatings. In vitro tests confirmed the mesenchymal stem cell (MSC) growth dependence on the characteristics of the coatings, revealing no cytotoxic effect. Acknowledgments: This work was supported by Romanian National Authority for Scientific Research (CNCS–UEFISCDI), under the projects PNII- PT-PCCA-2013-4-199, PN-II-RU-TE-2014-4-2434 and Nucleus programme.
Authors : Ignacio Falcón Casas, Martin Pfaffeneder-Kmen, Aida Naghilou, Günter Trettenhahn, Wolfgang Kautek
Affiliations : University of Vienna, Department of Physical Chemistry, Währinger Strasse 42, A-1090 Vienna, Austria
Resume : Graphene oxide is a promising precursor for the production of graphene. Photothermal and/or photochemical interactions using laser radiation may result in the photoreduction of graphene oxide . In the present study, the reduction of graphene oxide is demonstrated by near-field femtosecond laser irradiation . The laser beam was focused onto an atomic force microscope tip placed a few nanometers above the substrate. Near-field enhancement and/or thermal conduction below the tip induced the local reduction on graphene oxide nanosheets below the diffraction limit.  Y.-L. Zhang, L. Guo, H. Xia, Q.-D. Chen, J. Feng, and H.-B. Sun, Adv. Opt. Mater. 2 (2014) 10–28.  I. Falcón Casas and W. Kautek, „Apertureless scanning near-field optical lithography“, in „Laser micro-nano-nanomanufacturing and 3D microprinting“, (Ed.) A. Hu, Springer 2018.
Authors : Aida Naghilou, Oskar Armbruster, Stefan Solé, Wolfgang Kautek
Affiliations : University of Vienna, Department of Physical Chemistry, Waehringer Strasse 42, A-Vienna, Austria
Resume : Femtosecond pulse lasers provide a strongly growing field of applications in e.g. medicine, precision machining, photochemistry, and microscopy. Controlling the temporal shape of the pulse has been the subject of intensive research  and has led to important discoveries and applications . One of the leading techniques in controlling the pulse shape utilizing liquid crystal spatial light modulators . A complete manipulation of the phase and amplitude of each spectral component is possible . A temporal pulse shaper in combination with a high power oscillator has been designed and implemented. This novel system was applied for pulse compression and material processing with an evolutionary algorithm employing the transmission signal as feedback.  A.M. Weiner, D.E. Leaird, J.S. Patel, J.R. Wullert, Optics Letters, 15 (1990) 326-328.  W. WS, R. H, D. M., Science, 259 (1993) 1581-1589.  T. Baumert, T. Brixner, V. Seyfried, M. Strehle, G. Gerber, Applied Physics B, 65 (1997) 779-782.  M.M. Wefers, K.A. Nelson, Optics Letters, 20 (1995) 1047-1049.
Authors : E. Dutu 1, C. Fleaca 1, , F. Dumitrache 1 , C. Vlaic 2, M. Stich 2, A. Bund 2, I. Sandu 1, A. Ilie 1, A.-M. Niculescu 1, E. Vasile 3
Affiliations : 1 National Institute for Lasers, Plasma and Radiation Physics, Lasers Dept, Bucharest - Magurele, 409, Atomistilor Street, 077125, Romania; 2 Institut für Werkstofftechnik, FG Elektrochemie und Galvanotechnik, Technische Universitat Ilmenau; Germany; 3 "Politehnica” University of Bucharest, Faculty of Applied Chemistry & Material Science, Dept of Oxide Materials and Nanomaterials, 1-7, Gh. Polizu Street, 011061 Bucharest, Romania
Resume : Oxidic nanocomposite powders were obtained in a single step from tetramethyltin (TMT) and methyltrimethoxysilane (TMS) mixed vapors carried by ethylene (which plays also the sensitizer role) or nitrogen irradiated with an infrared laser beam in the presence of insufficient molecular oxygen. The XRD difractograms revealed the presence of both tin oxide tetragonal phases: rutile-type cassiterite SnO2 and romarchite SnO, as well as the less reported Sn3O4 phase and low amount of metallic β-Sn. Their core-shell morphology was revealed by TEM images, some of the cores being composed from aggregated very small nanocrystals, whereas the shells seem to be amorphous. Using HR-TEM, crystalline planes ascribed to SnO2 and SnO phases were identified in nanopowders. The Si-O bonds were identified in FT-IR spectra around 1000 cm-1 together with those assigned to Sn-O bonds (around 500 cm-1). The Raman spectra presented a large and convoluted peak (between 300 and 700 cm-1 Raman shift) attributed to a superposition from tin oxides and silicon oxide signals. Selected powders were used to prepare anode materials (mixed with carboxymethylcellulose and carbon black) which were tested in half-cell lithium ion batteries. The discharge capacity decreases from the initial values ~ 700 and 650 mAh/g to lower values ~ 550 and 500 mAh/g, respectively after 50 cycles. The lithiation-delithiation redox processes, as well as the solid electrolyte interface (SEI) layer formation were evidenced using cyclic voltammograms.
Authors : F. Andrei1,2, A. Vlad1, R. Birjega1, A.Matei1, V.C. Dinca1, M. Secu3, S. Brajnicov1, A. Rotaru1, V. Marascu1, M. Dumitru1, M. Dinescu1, R. Zavoianu2
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 3 National Institute for Materials Physics, P.O. Box MG-7, 77125 Bucharest-Magurele, Romania
Resume : Curcumin (CR) is a natural compound with a well known antioxidant and therapeutic activity. Recently it has been found that its stability may be enhanced when incorporated in LDH matrix . Curcumin intercalated layered double hydroxide nanohybrid as a potential drug delivery system for effective photodynamic therapy in human breast cancer or skin cancer. The synthesis of the hybrid LDH-CR powder implies the dissolution of CR in water or another organic solvent which is miscible with water. Since the solubility of CR in water is very weak, in this study we have aimed to investigate the effect of the solvent employed for its dissolution on the structural and physico-chemical properties of the resulting hybrid materials. Four powders of curcumin (CR)-containing Mg2.5Al-LDH hybrids (Mg/Al molar ratio of 2.5) were prepared by co-precipitation (P) and reconstruction (R) using two different solvents for the dissolution of curcumin: (i) an alkaline aqueous solution, and (ii) ethanol. The reconstruction used the calcinated (460oC for 18 h) form of the parent Mg2.5Al-LDH powder. All the solids were characterized by X-ray diffraction (XRD) , DR-UV-Vis and ATR FTIR spectrocopies and thermal analysis (TG-DTA) . The FTIR-ATR spectra of the all the powders except the powder prepared via reconstruction in ethanol exhibit LDH characteristics, consistent with the XRD results. Matrix Assisted Pulsed Laser Evaporation (MAPLE) was employed for the deposition of hybrid LDH-CR thin films. Aqueous solutions of the as prepared hybrid LDH-CR powders were frozen and used as targets for MAPLE depositions. The films were deposited at 266 nm. MAPLE is considered a "soft" deposition technique t suitable to conserve the CR stability. XRD, scanning electron microscopy, atomic force microscopy, FT-IR spectroscopy and photoluminescence measurements were used to characterize the deposited films in order to evindence the influence of the preparation methods on the structural and photophysical characteristics of the hybrid LDH-CR films. The controlled release of CR from the LDH-CR powders and films obtained by MAPLE in different pH buffers was also investigated.
Authors : Alina Ilie 1, Scarisoreanu Monica 1, Ana-Maria Banici 1,2, Claudiu Fleaca 1, Florin Andrei 1, Valentin Teodorescu 3, Lavinia Gavrila-Florescu 1, Elena Dutu 1, Florian Dumitrache 1
Affiliations : 1 National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania 2 University of Craiova, Faculty of Mathematics and Natural Sciences, Craiova, Romania 3 National Institute of Materials Physics, Magurele, Romania
Resume : The nano-TiO2 synthesis method tends to promote a certain crystalline phase formation, to the detriment of others. Laser pyrolysis of TiO2 previous studies  demonstrated the method’s ability to produce controlled mixed phase TiO2 nanoparticles, by experimental parameter modulation, presenting high thermal stability and a wide range of dimensions. This work proposes W/Ti oxide nanocomposites synthesis using resonant CO2 laser excitation of C2H4, for promoting simultaneous photo-excited processes of dissociation and nucleation for nanometric W and Ti oxides, with air as oxidizing agent. We follow the less studied W oxide crystalline phase predilection, within the pyrolytic process of nucleation, and its dependency of titania anatase/rutile ratio. The specific geometry of precursor injector and O2/sensitizer concentration produces distinctive nanocomposite morphologies and characteristics, as resulted from X-ray Diffraction, EDS, TEM and Raman spectroscopy analysis. TiO2 nanoparticles synthesized by laser pyrolysis have been proven to exhibit good photocatalytic activity , superior to those of commercial titania (P25 Degussa) or obtained by chemical synthesis methods. Several independent studies suggested that mixed phase anatase/rutile nano-TiO2 provides better photodegradation efficiency than pure anatase titania, especially in VIS light, while tungsten oxides enhances the semiconductor’s charge separation efficiency. Thus, our study aims to generate a nanocomposite that combines the advantages of both nanomaterials, with tunable crystalline phase percentages and W contents, for further photocatalytic purposes.  A.G. Ilie et al, Appl. Surf. Sci. 427 (2018) 798-806  M. Scarisoreanu,et al, Appl. Surf. Sci. 418 (2017) 491-498
Authors : F. Dumitrache-1, C. Fleaca-1, M. Balas-2, I. Morjan-1, A. Ilie-1, A. Dinischiotu-2, E. Tanasa-3, M. Enculescu-4, C. Locovei-1, C. Mihailescu-1, O. Marinica-5
Affiliations : 1 NILPRP, Atomistilor 409, Magurele Bucharest, Romania 2 University of Bucharest, Department of Biochemistry and Molecular Biology, Splaiul Independentei 91-95, Bucharest, Romania 3 University Bucharest, Faculty of Physics, Atomistilor 405, Magurele Bucharest, Romania 4 Politehnica University of Bucharest, Faculty of Applied Chemistry and Materials Science, Department of Oxide Materials and Nanomaterials, Gh. Polizu 1-7, Bucharest, Romania 5 University of Timisoara – Research Center for Engineering of Systems with Complex Fluids, Mihai Viteazul 1, Timisoara, Romania
Resume : Aggregates of spherical Fe carbides-Si hybrid nanoparticles (Fe-Si NPs) with a controllable mean sizes from 4 to 20 nm were synthesized by laser pyrolysis into a single step procedure. The resulted powders were also post-treated using controlled oxidation combined with inert gas annealing up to 800°C. Structural, morphological, elemental composition, magnetic and luminescence investigations on as synthesized or thermal treated Fe-Si NPs were performed in order to optimize the synthesis and thermal treatment parameters. In optimized conditions Fe-Si NPs with luminescence in near-IR to red color region and saturation magnetization up to 50 emu/g were obtained. Stabilized PBS based suspensions with 0.5 to 5 mg/ml powder concentration and around 150-350 nm mean aggregate dimension were prepared from Fe-Si NPs using sodium carboxymethylcellulose (CMCNa ) as stabilizer. In vitro screening tests regarding the toxicity, cell uptake and hyperthermia effect in human lung fibroblasts (MRC-5) and colorectal (Caco2) cancer cells were performed on PBS based suspensions with as synthesized or thermal treated Fe-Si NPs and stabilized with CMC-Na.
Authors : Monica Scarisoreanu1, Alina Ilie1,2, Claudiu Fleaca1, Iuliana Morjan1, Anca Badoi1, Ion Sandu1, Florin Andrei1, Ion Morjan1,Valentin Teodorescu 3.
Affiliations : 1 National Institute for Lasers, Plasma and Radiation Physics, 409Atomistilor Street, 077125 Magurele-Bucharest, Romania; 2 University of Bucharest, Faculty of Physics, 405 Atomistilor Str, Magurele-Bucharest, 077125, Romania; 3 National Institute of Materials Physics,405A Atomistilor Street, 077125 Magurele-Bucharest, Romania
Resume : This work presents the preparation of VO2/TiO2 composite nanoparticles using laser pyrolysis technique. The obtaining process was based on sensitized mixtures of TiCl4 and VOCl3 precursors in the presence of air. Nanocomposites with controlled V:Ti atomic ratios were produced at different synthesis parameters. Structural, morphological and optical properties of the obtained powders have been revealed by X-ray diffraction (XRD), scanning and high resolution transmission electron microscopy (SEM, HR-TEM), UV-VIS and ellipsometry spectroscopy techniques. The results indicate that the nanocomposite particles have a core-shell morphology contains a VO2 core and the TiO2 anatase shell. The variations of vanadium-titania phase led to the obtaining of a new photocatalyst with thermochromic properties for multifunctional smart coatings applications.
Authors : Thi Trang Dai Huynh, Nadjib Semmar
Affiliations : GREMI-UMR 7344 CNRS University of Orleans, 14 Rue d'Issoudin, BP 6744 45067 Orleans Cedex France
Resume : Copper and titanium thin films (with closely 200 nm thickness) are grown using magnetron-sputtering technique. Applying accumulative pulses with low and very low fluences (from 200 to 10 mJ/cm2), incubation curves were studied versus the beam wavelengths. The experiments are conducted under normal atmosphere, but using a heated holder with temperature ranging from room T° up to 200°C. The effect of temperature in increasing the incubation leading to film damage is investigated using SEM images ad also by combining surface dynamic reflectivity analysis with two laser probes at 633 and 478 nm wavelength. The heating laser used in this study is Nd:YAG laser (Continuum 1064 nm, 10 ns, 10 Hz) and the output beam is used from the fundamental wavelength to 266 nm using second, third, and quadruple harmonic generator. Even if the absorption of photons is slightly different in case of Cu and Ti films, first results returned different incubation behavior versus wavelength that are also sensitively affected by the substrate temperature. Additional physico-chemical analysis (Ellipsometry, AFM and contact angle) are proposed to help in the interpretation of the results at several stages of the beam accumulation.
Authors : S. Brajnicov1,2, C. Constantinescu1,3, A. Bonciu1,4, A. Moldovan1, V. Marascu1,4, N.L. Dumitrescu1,2, V. Dinca1 and M. Dinescu1,2
Affiliations :  INFLPR Natl Inst Laser Plasma & Radiat Phys, RO-077125 Magurele, Romania;  Univ Craiova, Fac Math & Nat Sci, Craiova 200585, Romania;  CNRS, University of Limoges, France;  Univ Bucharest, Fac Phys, RO-077125 Magurele, Romania;
Resume : In this work, the influence of laser fluence on the morphological and compositional characteristics of triblock copolymers (i.e. poly(lactide-co-caprolactone)- block-poly(ethylene-glycol)-block-poly(lactide-co-caprolactone) (PLCL-PEG- PLCL)) thin films obtained by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) is reported. The surface morphology of the deposited layers was investigated by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The surface chemistry was studied by Energy-Dispersive X-ray spectroscopy (EDX) and Fourier-Transform Infrared spectroscopy (FTIR). The layers obtained at fluences up 0.5 J/cm2 exhibit homogenous surfaces, while for fluences starting with 0.6J/cm2, "icosahedron" and cubic type structures were observed. The influence and the contribution of both fluence and Chlorine presence on the formation of the different types of structures with complex symmetry on the surface of the deposited layer is also discussed. Acknowledgements: This work was supported by a grant of the Romanian National Authority for Scientific Research and Innovation, CNCS/CCCDI - UEFISCDI, project number PN-III-P2-2.1-PED-2016-1715, within PNCDI III and Nucleus program.
Authors : Sergej Orlov, Alfonsas Juršėnas, Ada Gajauskaitė, Justas Baltrukonis
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 beams 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 needles”. In this work we with start with construction of an “optical needle”, which in contrary to a Bessel beam has an arbitrary intensity distribution. We analyze ways to change the spatial position of the “optical needle” 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 needles” 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 distortions caused by propagation through planar air-dielectric interface and attempt to compensate them.
Authors : N. D. Scarisoreanu1, F. Craciun2, F. Andrei1, A. Andrei1, V.Ion, R. Birjega1 , M. Dinescu1
Affiliations : 1 INFLPR, P.O. Box MG-16, RO-77125, Bucharest, Romania 2 CNR-Istituto dei Sistemi Complessi, Via del Fosso del Cavaliere 100, I-00133, Rome, Italy
Resume : BiFeO3 is one of the most promising multiferroic material exhibiting, however, drawbacks as low dielectric susceptibility, poor chemical stability and high dielectric loss. Recently, we have demonstrated that joining doping and epitaxial strain engineering a nanoscale stripe structure was induced, resulting in a significant improvement of the dielectric characteristics. By high resolution transmission electron microscopy (HR-TEM) we have evidenced nanostripe domains with alternating compressive and tensile strain in the Y-doped BiFeO3 epitaxial thin films. Small band gap values of bismuth ferrite (BFO) have triggered the interest due to the photovoltaic and photocatalytic potential, for pure or cation doped BFO. However, energy related properties of BiFeO3 can be improved by coupling the strong ferroelectricity of BFO with chemical stability and small band gap value of LaFeO3 within thickness graded heterostructures. Thin films of BFO on 5-20 nm thick epitaxial LFO films deposited on different strain-induced substrates, have been obtained by RHEED- assisted Pulsed Laser Deposition. Their functional dielectric, optical and photolytic behaviour has been unravelled in connexion with complex ensembles of nanoscale phase/nanodomain fluctuations within the epitaxial films.
Authors : N.E. Stankova*1, P.A. Atanasov1, Kr. Koev1, E. Iordanova2, G. Yankov2, E. Radeva2, M. Zamfirescu3, B.St. Calin3, C.R. Luculescu3, M.D. Dumitru3, Dr.Tatchev4, K.N. Kolev4, E.I. Valova4, St.A. Armyanov4, K. Grochowska5, G. Śliwiński5, N. Fukata6, D Hirsch7, B. Rauschenbach7
Affiliations : 1 Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko shousse blvd., 1784 Sofia, Bulgaria, 2 Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko shousse blvd., 1784 Sofia, Bulgaria, 3 National Institute for Lasers, Plasma, and Radiation Physics (INFLPR), Strada Atomistilor nr. 409 P.O. Box MG-54 RO-77125, Magurele, Romania, 4 Institute of Physical Chemistry, Bulgarian Academy of Sciences, block 11, Acad. G. Bonchev str., 1113 Sofia, Bulgaria, 5 Photophysics Department, The Szewalski Institute, Polish Academy of Sciences, 14 Fiszera St, 80-231 Gdańsk, Poland, 6 International Center for Materials for Nano Architectonics (MANA), National Institute for Materials Science (NIMS), 1-1Namiki, Tsukuba 305-0044, Japan, 7 Leibniz Institute of Surface Modification (IOM), 15 Permoserstrasse, D-04318 Leipzig, Germany
Resume : The research is focused on fundamental study of processes and effects of interaction of short and ultra-short laser irradiation with optical transparent nanocomposite biocompatible polymers. Laser generation from ultraviolet to near infrared regions of the spectrum is applied. The high optical transparency of the biopolymers in this range and the requirements for precision and high quality processing demands for knowledge of the mechanisms and physical processes during interaction of laser irradiation with the material. Changes in physical and chemical properties due to laser surface modification are experimentally and theoretically studied. Various process parameters (laser wave length, pulse duration, fluence and number of pulses) are examined. Complex data of successful modification and activation of the surface of PDMS elastomer by using traditional laser processing and subsequent successful functionalization of the laser modified surface are provided. The preliminary results show promising prospects of implementation of such laser-based methods for micro- or nano-processing of optically transparent biopolymers for interface devices in bioengineering technologies such as neural implants.
Authors : M. Dumitru1, L.N.Dumitrescu1,2, S. Brajnicov1,2, V.Marascu1,3
Affiliations : 1National Institute for Laser and Radiation, Bucharest, Magurele, Romania. 2University of Craiova, Faculty of Sciences, Craiova, Romania. 3University of Bucharest, Faculty of Physics, Bucharest, Romania
Resume : The specific characteristics of tin dioxide (SnO2) i.e. high chemical and thermal stability make it suitable for a large area of applications such as displays, optical-electronic devices, and gas sensors. In this work, we report on the morphological and structural properties of SnO2 thin films grown by matrix assisted by pulsed laser evaporation (MAPLE). The thin film samples were obtained from a frozen target of SnO2 nanoparticles in different concentrations (1-5% w/w) and water as a solvent. A parametric study was carried out based on target composition, laser fluence and number of pulses in order to find the optimal deposition parameters for obtaining uniform and continuous layers. Investigations by atomic force microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy evidenced that the thin films deposited by MAPLE could be used as active materials in gas sensors, with a high sensitivity and response speed to various analyses. Acknowledgement: PED 65/2017 “Modular Aircraft Platform for Intelligent Atmospheric Monitoring (MAPIAM)” Keywords: SnO2, thin films, MAPLE, gas sensor
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Materials Processing & Devices III : Jörg Hermann
Authors : Dave H.A. Blank
Affiliations : University of Twente
Resume : .
Authors : R. Lahoz (1), J.A. Cebollero (2), M. A. Laguna-Bercero (2), J. Silva (2), A. Larrea (2)
Affiliations : (1) Centro de Química y Materiales de Aragón (Universidad de Zaragoza – CSIC), C/ María de Luna 3, E-50.018 Zaragoza, Spain. (2) Instituto de Ciencia de Materiales de Aragón, (Universidad de Zaragoza – CSIC), C/ María de Luna 3, E-50.018 Zaragoza, Spain.
Resume : Solid Oxide Fuel Cells (SOFC) are ‘green’ electrochemical devices that transform hydrogen or other hydrocarbons into electricity with high efficiency and zero emission of pollutants. The cells are essentially formed by a dense solid oxide electrolyte and two porous electrodes. A typical cell configuration is an yttria-stabilised zirconia (YSZ) electrolyte, a Ni-YSZ fuel electrode and an YSZ-LSM (LSM: La1-xSrxMnO3) oxygen electrode. In this work we study the laser generation of patterned electrode-electrolyte interfaces in order to reduce cathode activation polarisation, which is one of the main contributions to the losses of a Solid Oxide Fuel Cell. A commercial computer-controlled Q-switched laser source emitting at λ=532 nm with 5 ns pulse width has been used to perform this patterning. Different micro-patterns, square and hexagonal arrays, on YSZ and Ni-YSZ plates have been tested. After that, symetrical cells have been prepared to determine their activation polarisation by Electrochemical Impedance Spectroscopy (EIS). Aspect ratio obtained by patterning is been also studied for the technological assessment of the future fabrication processes. Patterned cells show an improvement in the cathodic activation processes. The decrease in polarisation with respect to unprocessed ones is about 30%. Further studies are in progress to increase the contact surface and reduce the polarization.
Authors : Ian Napier, Victor Chang, Nicholas Harrison
Affiliations : Imperial College London
Resume : Free-electron lasers (FELs) can generate ultrashort, coherent, X-ray flashes that are continuously tuneable and a billion times brighter than those from the best synchrotron X-ray sources. They require a photocathode capable of generating bright, low emittance bunches of electrons so atomic systems can be studied on their natural length and timescales. Overall FEL performance is dictated by the quality of the initial electron beam, meaning improvements require further understanding of the photocathode emission process. In this work, a predictive theoretical approach developed by the Harrison Group, building on the Spicer three-step model, will be employed to study new photocathode materials. Density Functional Theory calculations will be used to relate the surface electronic structure of AgBa and CuBa to the photoemission process. Alloys constituting stable, high work function metals (Ag, Cu) paired with an unstable, very low work function metal (Ba) can lead to stable intermediate phases with desirable photocathode properties versus pure metals. Increased quantum efficiency, low work function and low emittance are desired from the alloys to be studied. Achieving these goals will allow higher energy beams to be produced or a reduction in length and therefore cost of FEL facilities.
Materials Processing & Devices IV : Marta Castillejo
Authors : Qingfeng Li, Anne-Patricia Alloncle, David Grojo, Philippe Delaporte
Affiliations : Aix-Marseille University, CNRS, LP3 UMR 7341, Marseille, France
Resume : Dual-laser induced forward transfer process consists in irradiating a solid thin film deposited on a transparent donor substrate by a first long duration laser pulse, to locally melt the film, followed by a second irradiation with an ultrashort laser pulse to initiate material transfer in the liquid phase toward a receiver substrate. This method has been recently demonstrated as a versatile method to print high-resolution (<2 µm) patterns with a large working distance (>40 µm). However, the printing dynamics associated with these performances is only partially understood so far. In this paper, we focus the investigations on this aspect allowing further optimizations. Two key parameters that influences the ejection dynamics are discussed. First, the temperature evolution of the thin copper film within a quasi-continues wave (QCW) pulse heating process is calculated and visualizations of ejection events under different temperatures reveal the influence of Cu temperature on the ejection dynamics. Second, for a given Cu temperature, by increasing the fluences of the femtosecond pulse, the visualizations reveal a fluence threshold under which no ejection is observed, followed by the release of a single droplet, multi droplets and ultimately the formation of a jet. With both droplet and jet modes of ejection, we show clean microstructures (no debris) successfully printed onto a Si receiver placed as far as 60 µm away from the donor film.
Authors : M. Makrygianni1, A. Kalaitzis1, I. Theodorakos1, A. Hatziapostolou2, S. Melamed3, A. Kabla3, F. de la Vega3, I. Zergioti1
Affiliations : 1)National Technical University of Athens, Physics Department, Zografou Campus Greece, 15780; 2)Technological Educational Institute of Athens, Department of Energy Technology Engineering, Ag. Spyridinos 28, 12243, Aigaleo, Athens, Greece; 3)PV Nano Cell Ltd., 8 Hamasger st., P.O. Box 236 Migdal Ha’Emek, 2310102 Israel
Resume : Novel printing methods represent a class of emerging technologies, with applications in the field of microelectronics, which are cost-effective techniques with the ability to deposit highly resolved features. Typically, popular printing technologies, such as inkjet printing, deposit only low viscosity fluids. In a broad range of emerging applications, alternative printing techniques would enable the handling of materials with much higher viscosities. Laser-induced forward transfer technique (LIFT) meets these requirements and has already been applied for the direct printing of devices and components. However, in order to improve the process’ reproducibility and printing resolution, further research has to be conducted, regarding the rheological characteristics of the printable fluids and their jetting dynamics. In this work, we employ both time-resolved and high-speed imaging in order to investigate the formation and expansion of the liquid bubble, as well as the liquid jet’s propagation. The study is carried out both for Newtonian and non-Newtonian fluids, for a big range of viscosities. From the time-resolved experiments, it was observed that fluid ejections are initiated by the rapid expansion of a micrometer-sized vapor bubble that forms for both types of fluids. High-speed imaging illustrated all the different types of ejection regimes which are influenced by the fluid’s metal loading, the fluid’s viscosity, fluid thickness on donor and laser fluence on donor. Furthermore, a computational model is also utilized in order to gain more insight on the transfer mechanisms of the process. The simulation predictions are validated against experimental results, being in good accordance with the latter ones. Finally, we present an overall methodology for process parameters on Newtonian and non-Newtonian fluids to offer a criterion for stable operation with LIFT technique.
Authors : J.M. Fernández-Pradas, P. Sopeña, P. Serra
Affiliations : Universitat de Barcelona, IN2UB, Departament de Física Aplicada, Martí i Franquès 1, 08028-Barcelona, Spain e-mail: email@example.com
Resume : Networks of silver nanowires (Ag-NWs) can be electrical conductive and optically transparent at the same time. Thus, Ag-NWs are promising candidates to substitute transparent and conductive oxides like indium-tin-oxide. Furthermore, they can be deposited on flexible substrates without losing their functionality. Lasers have been previously used to perform a selective sintering or selective ablation of formerly deposited Ag-NWs by other means such as spraying, screen-printing or spin coating. However, direct-write methods for printing patterns can be suitable in order to reduce the amount of material used. Attempts of printing Ag-NWs by means of inkjet required a previous sonication step in order to avoid clogging issues. However, the reduction of the Ag-NWs length compromises their optical and electrical performance. In this work, we propose the use of laser induced forward transfer for printing Ag-NWs in a digital manner without altering their original properties. Inks with different concentrations of Ag-NWs have been evaluated. The effects of the laser pulse energy on the printed material has also been studied. It has been found that the optical and electrical properties of the printed patterns basically depend on the concentration of Ag-NWs after drying. Different patterns and electrodes have been printed by LIFT with good optical and electrical characteristics comparable to those deposited by traditional methods in large areas.
Authors : J. Hermann (1), A. Taleb (1,5), E. Axente (2), V. Craciun (2), G. Bilge (3), I. H. Boyaci (4), F. Pelascini (5)
Affiliations : (1) LP3, CNRS – Aix-Marseille University, 13009 Marseille, France; (2) National Institute for Lasers, Plasma and Radiation Physics, 77125 Măgurele, Romania; (3) Nanosens Industry and Trade Inc., 06790 Ankara, Turkey; (4) Department of Food Engineering, Hacettepe University, 06800 Ankara, Turkey; (5) CRITT Matériaux Alsace, 67305 Schiltigheim, France;
Resume : The question whether precise modeling of laser-produced plasmas can be achieved using simple statistical laws of equilibrium is a subject of controversial discussions since the early experiments of laser-matter interactions . The successful description of spectral emission from laser plasmas by the model of local thermodynamic equilibrium observed in some cases  led to material analysis via so-called “calibration-free” laser-induced breakdown spectroscopy . Since the first report, more than hundred papers have been dedicated to the subject with a rather poor outcome: calibration-free laser-induced material analysis is nowadays considered as quantitative for major elements while it is qualitative or semi-quantitative for minor and trace elements. The precise reasons for the low measurement accuracy are not yet well identified. Due to the large variability of experimental conditions and sample materials, multiple sources of measurement errors have been reported. Among them, the non-validity of the model is often inferred. In a recent paper, we have shown that the properties of laser-induced plasma can be tailored to allow for precise modeling by choosing appropriate experimental conditions . Material ablation with ultraviolet nanosecond laser pulses in an argon atmosphere generates a plasma that is spatially uniform and in local thermodynamic equilibrium, two properties which are generally very difficult to achieve simultaneously. We took advantage of this “ideal” radiation source to investigate its use in analyses of complex materials via calibration-free laser-induced breakdown spectroscopy. A critical analysis of the measurement uncertainties is given and the perspectives of the application to materials such as glasses, alloys and organic materials (food) are discussed.  S. Elezier, A. D. Krumbein, D. Salzmann, J. Phys. D: Appl. Phys. 11, 1693 (1978).  J. Hermann, C. Boulmer-Leborgne, B. Dubreuil, I. N. Mihailescu, J. Appl. Phys. 74, 3071 (1993).  A. Ciucci, M. Corsi, V. Palleschi, S. Rastelli, A. Salvetti, E. Tognoni, Appl. Spectrosc. 53, 960 (1999).  J. Hermann, D. Grojo, E. Axente, C. Gerhard, M. Burger, V. Craciun, Phys. Rev. E 96, 053210 (2017).
Authors : Evgeniya Paulis, Ulrich Pacher, Morris J.J. Weimerskirch, Tristan O. Nagy, Wolfgang Kautek
Affiliations : University of Vienna, Department of Physical Chemistry, Währinger Strasse 42, A-1090 Wien, Austria
Resume : Rapid and precise stratigraphic analyses of metal coatings are accessible by Laser-Induced Breakdown Spectroscopy (LIBS) where the plasma emission data are converted into stratigrams [1,2]. This is demonstrated for copper and nickel coating systems on steel. A ns-pulse Nd:YAG laser (1064 nm and 532 nm) was employed. The ablation rate depends strongly on the wavelength. This cannot be explained by the optical absorption of the substrates. The thermal diffusion length together with plasma shielding can explain the observed behaviour semi-quantitatively. Plasma shielding affects the ablation process with the near-infrared wavelength in contrast to the visible case where it is negligible. These results show that the beam-plasma interaction not only plays an important role in the quantification of the ablation rate, the depth resolution and the analysis depth, but also in the plasma heating which itself affects the plasma emission efficiency.  T. Nagy, U. Pacher, H. Pöhl, W. Kautek, Appl. Surf. Sci. 302 (2914) 189-193.  U. Pacher, M. Dinu, T.O. Nagy, R. Radvan, W. Kautek, Spectrochimica Acta (2017), in press.
Materials Processing & Devices V : Maria Dinescu
Authors : C. Zwahr, Stefan Heilmann, A. Knape, J. Zschetzsche, Prof. Dr. A. F. Lasagni, Prof. Dr. U. Füssel
Affiliations : Institut für Fertigungstechnik, Technische Universität Dresden, George-Bähr Str. 3c, 01069 Dresden, Germany E-mail: firstname.lastname@example.org
Resume : The effort of automotive industry is the increasingly use of aluminum alloys to reduce the weight of the car. Regarding the lifetime of electrodes and the process reliability resistance, spot welding is not applied for joining of aluminum sheets. Instead, more expensive processes must be used, like riveting with supplementary component. This is caused by the electric isolating oxide layer at the sheet surface. This layer normally shows an irregular topography, causing a locale temperature increase and therefore high electrode wear. In this study, a new concept to increase the electrode lifetime and process reliability is reported. Using Direct Laser Interference Patterning, periodic surface patterns are produced at the contact area between the electrode and the sheet for influencing the contact resistance. By interfering two picosecond pulsed laser beams on the cupper electrode surfaces, line-like structures with a spatial period of 5 µm are produced. The resulting topography and morphology were analyzed by confocal microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The electrical resistance between the contact partners copper and aluminum was measured during spot welding tests and contact resistance studies. A reduction up to 50 % of the electrical resistance by treating the electrodes could be achieved compared to an untreated reference.
Authors : M. Gstalter, G. Chabrol, A. Bahouka, K-D. Dorkenoo, J-L. Rehspringer, S. Lecler
Affiliations : Laboratoire des sciences de l’Ingénieur, de l’Informatique et de l’Imagerie (ICube), Boulevard Sébastien Brant, Illkirch, FRANCE; IREPA LASER, Boulevard Sébastien Brant, Illkirch, FRANCE; Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Strasbourg, FRANCE; ECAM Strasbourg-Europe, Rue de Madrid, Schiltigheim, FRANCE
Resume : Glass welding by ultrashort laser pulses is a method of glass bonding developed in laboratory and currently adapted as an industrial process. This method presents many advantages in term of resistance, process speed, hermeticity and biocompatibility compared to the classical glass bonding technics. The principle relies on the nonlinear absorption of the focused laser beam at the interface of the glass plates to weld. The demonstration of this method has been realized on glass plates having very high roughness and flatness quality, to obtain an optical contact between the samples. The industrialization of the method involves to overcome this quality requirement and process glass plates with ordinary surface quality. The study focuses on the analyses of the properties differences between welding seams realized on optically contacted and non-contacted samples. Welded seams have been created in borosilicate glass using 300 fs duration pulses with a tunable repetition rate up to 2 MHz. Welding area on optically contacted samples can be inscribed at low energy and are completely transparent, but are limited in dimension by the optical contact. Welding of ordinary glass plates without optical contact can be created by increasing the energy. This reduces the transparence of the welding seams and increases the residual stress, but allows to generate large welding area. The samples have been analyzed by Raman spectroscopy and third harmonic generation microscopy.
Authors : M. Gstalter, A. Bahouka, D. Desroche, G. Chabrol, K-D. Dorkenoo, J-L. Rehspringer, S. Lecler
Affiliations : IREPA LASER, Boulevard Sébastien Brant, Illkirch, FRANCE; Laboratoire des sciences de l’Ingénieur, de l’Informatique et de l’Imagerie (ICube), Boulevard Sébastien Brant, Illkirch, FRANCE; Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Strasbourg, FRANCE; ECAM Strasbourg-Europe, Rue de Madrid, Schiltigheim, FRANCE;
Resume : Bonding of glass on semiconductor is of great interest for the field of MEMS development, but classical methods like anodic junction are not suitable for every combinations of materials. The welding of glass on semiconductor by laser pulses could offer an alternative presenting advantages in term of mechanical resistance, hermeticity and biocompatibility. The use of nanosecond laser pulses has first been demonstrated, where the semi-conductor only is melted by the absorption of the laser pulses. The bonding of glass on semi-conductor has then been demonstrated by femtosecond laser pulses, which is known to reduce the heat affected zone and thus reduce the residual stress in the materials. The study focuses on the comparison on the welding formation process, by analyzing the welding seams by Raman spectroscopy. The shift and the broadening of the typical Raman peak of Silicon at 520 cm-1 can be linked to the residual stress in the material after processing. The experiments have been conducted on borosilicate glass and silicon, with a femtosecond laser generating 300 fs duration pulses at a tunable repetition rate up to 2 MHz, and a tunable wavelength between 515 and 1030 nm. The samples have been compared to those produced by a nanosecond laser generating 30 ns duration laser pulses at 1064 nm. The shift of the Raman spectra of the pristine materials and of the welded seams have been analyzed, highlighting the advantages of femtosecond laser welding over nanosecond.
Authors : A. La Magna1), S. F. Lombardo 1), I. Deretzis 1), A. Verstraete 2), B. Lespinasse 2), K. Huet 2)
Affiliations : 1) CNR-IMM, Catania, Zona Industriale VIII Strada 5 Catania, Italy 2) SCREEN-LASSE, SCREEN Semiconductor Solutions, Co., Ltd., Gennevilliers, France
Resume : Sub-µs Laser annealing (LA) is the preferred annealing technique in nano-electronics when strongly localized heating is needed in the manufacturing process flows. The application of such process in future electronic device generations is hindered by the difficulties in the process control and understanding. Accurate modelling is mandatory for process optimization and a seamless integration in the manufacturing flow.. Modelling development is a difficult task since devices are characterized by complex 3D structures with ~nm wide elements made of different materials/phases which may see their properties changing during the annealing process. We present a computational tool (LIAB: LASSE Innovation and Application Booster) for the simulation of LA process. This is a complex self-consistent problem, where the heating is evaluated by means of a self-consistent solution of the time harmonic solution of the Maxwell equations. The self-consistency derives from the dependence of the optical constant on the temperature, the phases (amorphous, crystal, liquid) and the alloy fraction. The main features of the package are: • Many materials calibration as a function of T and phases; • Coupling with Electromagnetic Simulations in 2D and 3D nano-structured topographies; • Multiple-dopant models simulating atoms diffusion solubility and segregation; • Alloy model (e.g. SiGe) and multiple phases; Some application cases will be discussed in order to demonstrate the potentiality of the package.
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