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2022 Spring Meeting



Fundamental and applicative research in laser-material interactions

This proposed Laser symposium aims at reuniting leading scientists, researchers, and laser users from academia and industry to share their most recent progress in laser-material processing and synthesis at any length (from the nano to macro level) and temporal (continuous wave to attosecond) scale. This symposium will focus both on fundamental as well as practical aspects of laser material processing, i.e. from biomedicine to eco-nano-technologies.


The "Fundamental and applicative research in laser-material interactions" symposium is intended to cover a wide range of topics focused on fundamental and applicative aspects of laser-material-interactions. 

The topics of the proposed symposium include, but are not limited to, laser-based materials synthesis, surface structuring and functionalization, process analytics and materials diagnostics with a special emphasis on both the micro- to nano-scale and continuous wave to attosecond scale. Special attention is focused towards recent progress in the fundamental mechanisms underlying in the laser-material-interaction, as well as on "hot topics" such as laser processing of novel materials aiming at the fabrication of photovoltaic cells, thermoelectric devices, systems for energy storage and conversion, sensors and biosensors, or new smart optics. This symposium shall bridge the works of fundamental or technological importance from across different areas of laser material interactions such as additive manufacturing, LIPSS formation, laser synthesis of colloids, laser transfer of soft materials and systems, and more emerging ultra-short, ultra-high-power laser-material interactions.

Among the highlights of the Laser symposium are the presentations of leading scientists from physical sciences, as well as the contributed and poster presentations. Particular attention shall be given to presentations submitted by young scientists with high-impact works. Similar to the previous years, the submitted papers will be published in a refereed ISI journal.

This symposium shall represent an interdisciplinary and multidisciplinary platform for researchers and scientists from Europe and worldwide to present their experimental works and theoretical contributions in a friendly and captivating atmosphere.

Hot topics to be covered by the symposium:

  • Ultra-short, ultra-high power laser-material interactions: from fundamentals to applications in various fields (e.g. environment, materials science, biology),
  • Laser 3D machining for MEMS, MOEMS, photonic crystals, and photonic applications,
  • Laser Induced Forward Transfer of materials and devices,
  • Laser/plasma production of thin films, nanoparticles, nanocomposites and novel nanomaterials
  • Laser/plasma modification of surfaces and films including organic compounds and biomaterials
  • Modelling of laser-materials interactions and basic mechanisms
  • Processing with ultrashort laser pulses,
  • Time-resolved diagnostics of laser processing,
  • Laser machining in industry,
  • Laser additive manufacturing,
  • Applications of laser-induced surface structures,
  • etc ...

Tentative list of invited speakers:

In the symposium program there will be approximately 11 invited talks. In addition, we intend to upgrade form oral presentation to invited presentation 3 of the best submitted abstracts. At present, we consider the following invited speakers:  

  • Romain Quidant, The Institute of Photonic Sciences (ICFO) and University of Barcelona, Barcelona, Spain
  • Tobias Voss, Braunschweig University of Technology, Braunschweig, Germany 
  • Nadezdha Bulgakova, HiLASE, Czech Republic
  • Thomas Lippert, Paul Scherrer Institute, Switzerland
  • Olivier Uteza, LP3 - Lasers, Plasmas et Procédés Photoniques, Aix-Marseille Université, France
  • Johannes Heitz - Johannes Kepler University Linz, Austria
  • Andres Fabian Lasagni, Professor for Laser Structuring in Manufacturing Technology at the Institute of Manufacturing Technology, Technical University of Dresden, Germany
  • Petru Ghenuche - ELI-NP, Romania


Selected papers will be published in Applied Phys. A (Springer).



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08:45 Welcome and Introduction to the Symposium    
Pulsed laser deposition and ablation-based growth of materials : Palla-Papavlu Alexandra
Authors : Thomas Lippert
Affiliations : 1- Division for Research with Neutrons and Muons, Paul Scherrer Institute, 5232 Villigen, Switzerland 2- International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka 819-0395, Japan 3- Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland

Resume : A number of methods from large scale facilities require the application of well-defined samples, controlling crystallinity, roughness to interface quality, requirements which can be fulfilled by thin films. We apply PLD to create these thin films to utilize complementary techniques, ranging from neutron reflectometry to grazing incidence X-ray absorption spectroscopy, and angle resolved photon emission spectroscopy. The material system which we study are oxynitrides which are applied as photoanodes in photo-electrochemical water splitting. Shortcomings of this material class are a fast decay in activity over the first few electrochemical cycles and a decay on the long term. While the long-term decay is possibly related to a degradation of the material, i.e., a loss of nitrogen, the fast decay is not really understood, and therefore also no approach can be envisioned how to overcome this problem. We studied the fast decay of the material (and first approaches how to prevent this) by using thin films as model system. For this approach we developed a method on: • How to deposit oxynitrides with well-defined oxygen content and crystallographic orientation by PLD using NH3 as reactive gas component on conducting substrates. • Design a cell for in-situ NR and in-situ/operando GIXAS (and modulation excitation, ME-XAS). • Measure the thin films before/after photoelectrochemical operation with NR and ARPES and before/after/during operation using GIXAS and ME-XAS.

Authors : I.A. Bercea*1, M. L. Ciurea2 , A.M. Lepadatu2, M. Dragoman3. M. Filipescu1, V. Ion1, A. Moldovan1, V.A. Maraloiu2 , V.S. Teodorescu2, Maria Dinescu1*
Affiliations : 1 National Institute for Laser, Plasma and Radiation Physics, Atomistilor 409, 77125 Magurele, Romania 2National Institute of Material Physics, Atomistilor 405 A, 77125 Magurele, Romania 3National Institute for Research and Development in Microtechnologies - IMT, Str. Erou Iancu Nicolae, Nr. 126 A, Voluntari, Ilfov, Romania

Resume : Graphene-ferroelectric heterostructures can be successfully used in improving the functionalities of graphene-based transistors/devices. The properties of the ferroelectric surface layer and the growth/transfer process of graphene on it are of paramount importance for obtaining nanoelectronic devices with enhanced properties and functionalities. HfO2 was recently found to exhibit, in certain structures and combinations, attractive ferroelectric properties, compatible with graphene-based transistors/devices. A parametric study regarding the deposition of very thin (pure or embedded in different heterostructures) HfO2 layers (thicknesses in the nm-tens of nm range) directly on Silicon substrate, with very low roughness and appropriate ferroelectric properties was carried out. A comparison between properties of layers grown by Pulsed Laser Deposition and those obtained by magnetron sputtering (as it results from AFM, PFM, SEM, HRTEM, XRD spectroellipsometric investigations) has been also done.

Authors : Stefan Andrei Irimiciuc(1,2), Sergii Chertopalov(2), Michal Novotný(2), Maricel Agop(3), Valentin Craciun(1,4), Jan Lancok(2)
Affiliations : 1National Institute for Laser, Plasma and Radiation Physics – NILPRP, 409 Atomistilor Street, Bucharest, Romania 2Institute of Physics of the Czech Academy of Sciences, Na Slovance 1999/2, Prague, Czech Republic 3Department of Physics, “Gh. Asachi” Technical University of Iasi, 700050 Iasi, Romania 4Extreme Light Infrastructure for Nuclear Physics, IFIN-HH, Magurele, Romania

Resume : Langmuir probe (LP) method was evaluated as a deposition sensor for pulsed laser deposition (PLD) technique in a wide range of pressures used during the growth of films. Angle-and time-resolved investigations were performed in order to develop plasma-thin film deposition recipes. Microsecond modulations were observed in the reconstructed I-V characteristic attributed to non-equilibrium dynamics of the ejected charges. This plasma regime is defining a non-equilibrium state which decreases/diminishes in time and with background gas addition. Time resolved investigations revealed the presence of a perturbative regime which is recorded for working pressures higher than 2 Pa where ionic bursts are observed in the electron saturation region. A non-linear dynamic’s analysis was performed on the perturbative regime and the strange attractors of the used model were reconstructed. The attractors are defined by two branches which become interconnected as the Ar pressure is increased. The working atmosphere plays the role of a coherence medium corelating short and long-time nonlinear behavior. The calibration results for LP were implemented for in-situ control of high-quality copper halide thin films production in various Ar pressure, from 10−5 Pa - to10 Pa) range at room temperature. The deposited films were characterized by XRD, AFM, SEM, XRF, XPS, Hall measurements, photoluminescence, transmission and reflections spectroscopy and ellipsometry. The attention was focused on the effect of angular distribution of the plasma properties on the spatial resolution homogeneity of the properties of the films. The Cu vacancies play a significant role in the p-type conductivity of CuI and CuBr films. The surface analysis investigation revealed a congruent transfer from the target coupled with a good crystallinity of the films and good electrical properties. The halide plasmas present some complex features of the ionic cloud as observed by unbiased probe analysis as a time-of-flight measurement tool. Each feature corresponds to an ionization state of the Cu and halide ions, results confirmed by spectroscopic investigations performed along the main propagation axis and discussed in the framework of multiple double layer formation during plasma expansion. The nature and pressure of each used gas influenced the plasma emission in a unique manner, which was further correlated with the data collected by the electrical measurements. This work was supported by Romanian Ministry of Education and Research, under Romanian Nat. Nucleu Program LAPLAS VI –n. 16N/2019, ELI-RO_2020_12 and PD 145⁄2020. We acknowledge the Operational Program Research, Development and Education financed by European Structural and Investment Funds and the Czech Ministry of Education, Youth and Sports SOLID21.

Authors : Curcio, M. *(1), De Bonis, A.(1), Pepe, A.(1), Bochicchio, B.(1), Laezza, A.(1), Teghil, R.(1), Santagata, A. (2), Rau, J.V.(3).
Affiliations : (1) Dipartimento di Scienze, Università della Basilicata, V.le dell’Ateneo Lucano 10, 85100 Potenza, Italy (2) ISM-CNR, UOS Tito Scalo, Zona Industriale, 85050 Tito Scalo (PZ), Italy (3) ISM-CNR, Via del Fosso del Cavaliere, 100-00133 Rome, Italy * lead presenter

Resume : In the past decades considerable advances in the development of materials for tissue regeneration have been made. However osteochondral tissue repair still requires a innovative approaches that taking into account the different involved layers: articular cartilage, cartilage-bone interface and subchondral bone. Therefore the production of multifunctional scaffolds mimicking the stratified anatomical architecture seems to be a valid approach for osteochondral tissue regeneration. Therefore we produced biphasic scaffold to improve the interface integration between the chondral and bony layers in the osteochondral unit. At this purpose, we conjugated two different methodologies: electrospinning, to fabricate a nanofibrous polymeric scaffold, and Pulsed Laser Deposition (PLD), to tune the composition and the morphology of the bone exposed surface. Electrospun multicomponent scaffold composed of synthetic and natural polymers has been proposed to join the good biocompatibility, biodegradation and good mechanical properties of poly (D,L- lactic acid) (PDLLA) and the hydrophilicity and cellular affinity of gelatin (GE). Then we coated one surface of the electrospun scaffold with a thin film of an inorganic bioactive glass supplemented with manganese ions for improving bone tissue healing. The properties and composition of the biphasic scaffold were investigated and its in vitro bioactivity in terms of induced mineralization was tested by soaking it in simulated body fluid (SBF). The kinetics of the inorganic film dissolution and the calcium phosphate phases growth were followed by microscopic and spectroscopic techniques, confirming that a combination of bioactive glass-ceramics and nanofibrous scaffolds holds promising potential for inducing mineralization in osteochondral tissues.

Authors : Anouar Hajjaji1*, Safa Jemai1, Mabrouk Laabidi1, Khaled Trabelsi1,Mounir Gaidi4, Aymen Amine Assadi3, Brahim Bessais1, and My Ali ElKhakani2
Affiliations : 1 Laboratoire de Photovoltaïque, Centre de Recherches et des Technologies de l'Energie, Technopôle de Borj-Cédria, BP 95 Hammam-Lif, 2050 Tunis, Tunisie 2Centre Énergie Matériaux et Télécommunications (INRS-EMT), Institut National de la Recherche Scientifique (INRS), 1650 Boulevard Lionel Boulet, Varennes, QC J3X 1S2, Canada 3 Univ Rennes, ENSCR, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226, F-35000, Rennes, France 4Center of Advanced Research Materials, Research Institute of Sciences and Engineering, University of Sharjah, Sharjah P.O. Box 27272, United Arab Emirates

Resume : This work investigated the photocatalytic performance of PbS-NPs/NTs-TiO2 photocatalysts, evaluated for the removal of Butane-2, 3-Dione (BUT). We report the effect of decorating Titanium dioxide nanotubes (TiO2-NTs) with lead sulfide nanoparticles (PbS-NPs) on photocatalytic degradation of volatile organic compounds (VOCs). TiO2-NTs have been synthesized using the electrochemical anodization process of the titanium substrates. PbS-NPs were deposited using the pulsed laser deposition (PLD) method. By increasing the number of laser ablation pulses (NLP) from 500 to 10000, the average size of the PbS-NPs was increases. The X-ray diffraction analysis has confirmed the crystalline quality of the PbS-NPs, whereas the Scanning electron microscopy (SEM) observations showed that the increase of the number of laser ablation pulses leads to the aggregation of the PbS-NPs together. AFM measurements shows the surface morphology of the PbS are compact, uniform, and have good adherence to the substrate. The section analysis shows that roughnesses are 52 nm for pure TiO2-NTs while it increases to 111 nm for NLP= 5000 and 22 nm for NLP=10000. The photoluminescence (PL) spectra shows that the PbS-NPs/TiO2-NTAs presents a lower PL intensity than the pure NTs, with a lowest PL intensity showed for NLP=5000. The Absorbance spectra of TiO2-NTAs after peeling and adhering upon quartz substrate shows that the band gap of TiO2 was estimated to be 3.1eV. At an optimized PbS-NPs laser pulses (NLP= 5000), the catalyst exhibits a high photocatalytic efficiency for BUT removal. The BUT degradation results show that the PbS-NPs-modified TiO2-NTs possess the higher BUT adsorption and degradation capacity than the pure TiO2-NTs. In addition, PbS-NPs/TiO2-NTs-5000 pulse shows the largest photocatalytic activity with more than 75%.

10:30 Q&A    
10:45 Coffee Break    
MAPLE, Nanoparticle Generation and Applications : Evgeny Gurevich
Authors : C. Craciun1,2, F. Andrei1,3, A. Bonciu1,2, S. Brajnicov1, M. Filipescu1, A. Palla Papavlu1, M. Dinescu1
Affiliations : 1 - National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania 2 - University of Bucharest, Faculty of Physics, RO 077125 Magurele, Romania 3 - Faculty of Chemistry, University of Bucharest, Romania

Resume : Nowadays, nitrites are widely studied for their applications in food and chemical industries, but also for their potential toxicity. In order to monitor the presence of nitrites in water, food and environmental system, many methods for detection were designed. In particular, electrochemical sensors represent alternative tools for nitrites detection in water due to their low cost and high portability. In this paper, we report on the processing and testing of sensors based on carbon nanotubes (CNT) for nitrites detection in water. The sensing membranes were obtained by matrix-assisted pulsed laser evaporation (MAPLE) technique on specific commercial platforms with electrodes. Compositional and morphological investigations regarding the properties of the obtained membranes based on a mixture of CNT, chitosan, and Iron (II) phthalocyanine (C32H16FeN8) have been carried out. The morphological investigations evidenced specific structures (“worm”-like and rods) corresponding to the nanostructured materials (CNT and C32H16FeN8) that are used to produce the active layers for sensors. By combining the properties of phthalocyanine, chitosan, and carbon nanotubes with the numerous advantages of the MAPLE technique, the final sensor showed notable improvement in response for nitrite detection in a buffer solution of pH4. This work was supported by grants of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, Project Number 459 PED/2020 (AWISEM) within PNCDI III and the Romanian National Nucleus Program

Authors : M. Alfè, G. Minopoli, V. Gargiulo, U. Caruso, G. Ausanio
Affiliations : Istituto di Scienze e Tecnologie per l’Energia e la Mobilità Sostenibili (CNR-STEMS), 80125 Naples, Italy; Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Via Pansini, 5, Naples, 80131, Italy; Department of Chemical Sciences, University of Naples Federico II, via Cinthia 4, 80126, Naples, Italy; Department of Physics “E. Pancini” University of Naples Federico II, via Cinthia 4, 80126, 80126 Naples, Italy.

Resume : Matrix-assisted pulsed laser evaporation (MAPLE) is a solvent-free technique particularly suitable for obtaining homogeneous, ultra-thin, well adherent coatings over any desired substrate by maintaining the chemical structure and the physiochemical properties of the deposited material. MAPLE is a versatile approach assuring many benefits over conventional methods (drop casting, dip-coating, spin coating, Langmuir–Blodgett dip-coating) for manufacturing multifunctional coatings on flexible supports including medical devices. It was also demonstrated to be suitable to safety deposit functional delicate enzimatic target [1] or polymer nanocapsules for light-induced release [2] for biological smart application. Graphenic coatings are a convenient approach combining easy manufacturing and tuning versatility but the biocompatibility of the graphene related material (GRM) pool is a still open task. Recently, a new class of GRM, namely graphene-like (GL) layers has been proposed [3]. GL-layers consists of short nanometric-sized graphene stacked layers and are obtained from a controlled top-down demolition of a nanostructured carbon black, have shown peculiar chemical-physical properties including biocompatibility on a vertebrate model [4] and biofilm growth inhibition [5]. For these peculiarities GL-layers are, differently from the most GRM, promising biosafe nanomaterials as they are or combined in hybrid materials [6], forecasting feasible applications as biosensors and nanomedicine, including drug delivery, and bioimaging. Moreover, GL layers are produced in water environment and they are suitable for bulk production at low costs. The production of functional coating on invasive medical devices as indwelling urinary catheters is particlarly attracting in the ambitious framework of antibiotics-free approaches and prevention of nosocomial infection driven by cathererizaton. In this study, MAPLE was used to deposit GL layers on silicone slices mimic catheters devices. The GL layers were inspected by a biological survey toward target cellular lines indicating that the GL-layer not lead to any perturbations in the different biological parameters evaluated, including citototoxic potential. As concern the coating on the silicone slices, data indicates that the proposed approach offers a tight control of the relevant chemical-physical features of the deposit (controlled by FTIR and AFM) and that these characteristics were maintained after MAPLE deposition. These results and the possibility to futher functionalize the GL-layers or combine them in hybrid fashion to assure a tigher adhesion to the substrate for use in harsh conditions, open to practical application of these new-concept devices for wide medical applications (drug delivery, next generation flexible devices, multifuctional coatings). References: [1] G. Ausanio, V. Califano, A. Costantini, G. Perretta, A. Aronne, G. P. Pepe, F. Sannino, L. Vicari, Matrix-assisted pulsed laser evaporation of β-glucosidase from a dopa/quinone target, Enzyme Microbial Technology, 2020, 132, 109414. [2] V. Marturano, F. Abate, V. Ambrogi, V. Califano, P. Cerruti, G.P. Pepe, L.R.M. Vicari, G. Ausanio, Smart Coatings Prepared via MAPLE Deposition of Polymer Nanocapsules for Light-Induced Release. Molecules. 2021, 26, 2736. [3] M. Alfè, V. Gargiulo, R. Di Capua, . Chiarella, J.N. Rouzaud, A. Vergara, and A. Ciajolo, Wet Chemical Method for Making GL Films from Carbon Black. ACS Appl. Mater. Interfaces 2012, 4 (9), 4491. [4] M. d’Amora, M. Alfe, V. Gargiulo and S. Giordani, GL layers from carbon black: in vivo toxicity assessment, Nanomaterials 2020, 10(8),1-9, 1472. [5] M. Olivi, M. Alfè, V. Gargiulo, F. Valle, F. Mura, M. Di Giosia, S. Rapino, C. Palleschi, D. Uccelletti, S. Fiorito, Antimicrobial properties of graphene-like nanoparticles: coating effect on Staphylococcus aureus. J. Nano. Res. 2016, 18 (12), 358. [6] V. Gargiulo, M. Alfè, R. Di Capua, A. R. Togna V., Cammisotto, S. Fiorito, A. Musto, A. Navarra, A. S. Parisi, A. Pezzella. Supplementing π-systems: eumelanin and graphene-like integration towards highly conductive materials for the mammalian cell culture bio-interface. Journal of Materials Chemistry B 2015, 3, 5070–5079.

Authors : M. Socol1, N. Preda1, C. Breazu1, G. Petre1, A. Stanculescu1, A. Stochioiu2, G. Socol2, S. Iftimie3 C. Thanner4, O. Rasoga1
Affiliations : 1National Institute of Material Physics, 405A Atomistilor Street, 077125, Magurele, Romania 2National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, 077125, Magurele, Romania 3University of Bucharest, Faculty of Physics, 405 Atomistilor Street, P.O. Box MG-11, Magurele, 077125 Romania 4EVGroup., DI Erich Thallner Strasse 1, 4782 St. Florian am Inn, Austria

Resume : Lately, there is a growing interest in the organic photovoltaic (OPV) cells due to the organic materials properties and compatibility with various types of substrates. However, their efficiencies are low relative to the silicon ones, therefore is still room for some improvements in this field. The micro/nano texturing of the electrodes using various geometries is one of the main ways to increase the optical absorption in the organic active layer. In principle, patterning the surface of the transparent electrode it increases the optical path length in the active film and the number of created excitons. Between the patterning techniques, the UV-nanoimprint lithography remains one of the fast and cheapest that can be applied on small or large areas. In this context, we studied the behaviour of some organic thin films deposited by matrix assisted pulsed laser evaporation (MAPLE) on flat and patterned ITO substrates. Moreover, the influence of an additive (1,8-diiodooctane) on the morphology of the obtained organic layers was analyzed. The optical investigations proved that the films present the specific absorption properties of the polymer (P3HT). Regarding the morphology of fabricated layers, as was expected, this is influenced by the used deposition substrate and by the presence of the additive. The obtained results showed that the prepared layers could find application in the field of the photovoltaic devices.

Authors : A. Stanculescu(1), M. Socol(1), C. Breazu(1), O. Rasoga(1), G. Petre(1,5), G. Socol(2), G. Popescvu-Pelin(2), N. Preda(1), L. Vacareanu(3), M. Girtan(4), F. Stanculescu(5)
Affiliations : (1) National Institute of Materials Physics, 105 bis Atomistilor Street, P.O. Box MG-7, Bucharest-Magurele, 077125 Romania,; (2)National Institute for Laser, Plasma and Radiation Physics, Str. Atomistilor, Nr. 409, PO Box MG-36, Magurele, Bucharest, 077125, Romania; (3) P. Poni Institute of Macromolecular Chemistry, 41 A Gr. Ghica Voda Alley, 700487-Iasi, Romania; (4)University of Angers, Photonics Laboratory, University 2, Bd. Lavoisier 49045, Angers, France; (5) University of Bucharest, Faculty of Physics, 405 Atomistilor Street, P.O. Box MG-11, Bucharest-Magurele, 077125 Romania

Resume : Bulk heterojunction (BHJ) active layer has effect on the electrical properties of the organic devices because it favors the exciton dissociation and transfer of generated carriers from one molecule to another to reach the electrodes. Thus, the use of new donor:acceptor combination for active layer represent an alternative for improving the devices' performances. Although the mostly used fullerene derivatives acceptors show trap-free electron transport, their relative low optical absorption limits the efficiency. Perylene diimides are promising acceptors, as they combine the higher absorption and stability with good solubility and deeper position of the lowest unoccupied molecular orbital, avoiding the electron trap level located at ∼3.6 eV. Therefore we investigated the properties of BHJ prepared with oligoazomethine donors, characterized by a central unit of 2,5-diamino-3,4-dicyanothiophene and electron donating triphenylamine or carbazole groups at both end, and perylene tetracarboxidiimide, a non-fullerene acceptor, mixed in weight ratio of (1:2), (1:3) and (1:4). These layers were deposited on ITO covered flexible substrates by Matrix-assisted pulsed laser evaporation (MAPLE) using chloroform as solvent and the radiation =248 nm of KrF* excimer laser (fluence=300 mJ/cm2, number of pulses=5000). Spectroscopic (UV-Vis, PL, FTIR) and I-V measurements confirmed that these BHJs prepared by MAPLE are adequate for solar cells applications, emphasizing the effect of composition.

Authors : Averchenko A.V. * (1), Salimon I.A (1), Zharkova E. V. (1), Abbas O.A. (1), Lagoudakis P. G. (1), Gladush Y. (1), Mkrtchyan A. A. (1), Nasibulin A. G. (1), and Mailis S. (1).
Affiliations : (1) Skolkovo Institute of Science and Technology, Moscow, 121205, Russian Federation

Resume : Transition metal dichalcogenides (TMDs) constitute a subcategory of layered materials, which have attracted much attention lately due to their compositional tuneability that allows tailoring of their optical and electrical properties and extend their optoelectronic utility throughout the visible and IR spectral range. Ultra-thin films of these materials can either be exfoliated from epitaxially grown bulk crystals, or grown using methods such as chemical vapor deposition or thermolysis of single source liquid precursors. One of the attractive features associated with layered materials is their combinatorial aspect, where layers of different compositions can be combined to form a composite with tailored properties to address various applications. There are several examples in the literature demonstrating the formation of such superstructures that utilize layered materials with different compositions. Moreover, this combinatorial aspect can be extended to nanomaterials with non-planar geometries such as carbon nanotubes. Recently there has been reports associated with the synthesis of TMD, which is based on the localised dissociation of single source precursors in ambient conditions using a laser source. In these reports (NH4)2MoS4 and (NH4)2WS4 thiosalts, which have been diluted in organic solvents, were used to produce tracks of MoS2 and WS2 ultra-thin films respectively by irradiation with a c.w. laser source. Here, we report the synthesis of a composite material that consists of a single wall carbon nanotube (SWCNT) network and TMDs (MoS2 and WS2). The composite has been produced using this laser based synthesis method in ambient conditions. In this implementation the precursor solution wets the SWCNT network during a spin-coating preparation step. The precursor-SWCNT complex is subsequently irradiated locally by visible laser radiation, which dissociates the precursor to form TMD films that appears to conform with the topography of the SWCNT network. Raman spectroscopy revealed the presence of both MoS2 and SWSNTs within the laser irradiated track. A detailed nano-structural and electrical characterisation of the resulting composite material will be presented. The authors acknowledge financial support from the Russian Science Foundation (RSF) (grant No. 21-79-20208).

Authors : Stankevičius, E* (1), Petrikaitė,V. (1), Trusovas R. (1), Adomavičiūtė-Grabusovė, S (2), Šablinskas, V. (2), Zdaniauskienė, A. (1), Talaikis, M. (1), Mikoliūnaitė, L. (1), Selskis, A. (1), Niaura, G. (1,2)
Affiliations : (1) Center for Physical Sciences and Technology (FTMC), Lithuania; (2) Institute of Chemical Physics, Faculty of Physics, Vilnius University, Lithuania; * lead presenter

Resume : Metal nanoparticles (NPs) are widely used in various technologies: advanced catalysts, treatment and diagnosis of cancer, targeted delivery of drugs, biolabeling, electrochemical sensors, and in many types of spectroscopy. NPs can be obtained in several different ways. Reducing and stabilizing reagents used in chemical synthesis often preclude the further application of NPs in analysis. Laser ablation provides an effective and ultra-clean way to generate nanoparticles crucial in modern technologies. The selection of target metal and ablation conditions can modulate NPs properties or even produce hybrid NPs. Magneto-plasmonic nanoparticles are one of the most promising nanoparticles due to their versatility. Such nanoparticles can be guided and concentrated with the magnetic field to a specific location where they could be used as electric field enhancers, for example, in Raman spectroscopy. We present a generation of NPs based on laser-ablation from magnetron sputtered thin metallic films and their use in Surface-Enhanced Raman Spectroscopy (SERS). Using 1064 nm 10 ps laser pulses focused on a target made of Glass/Fe/Au/ layers in acetone, the hybrid magneto-plasmonic nanoparticles were obtained. SEM and X-Ray diffraction spectroscopy results show that the produced NPs have a relatively wide size distribution, ranging from 10 to 200 nm for the Au core and from 2 to 10 nm for the Fe shell. The optimal Au/Fe ratio was sought after by examining SERS enhancement of model compound 4-mercaptobenzoic acid and magnetic properties using a strong non-uniform magnetic field. The optimal number, thickness, and order of magnetron deposited metal layers were revealed. We found that the use of acetone resulted in the most stable NPs among other tested solvents of different polarity.

12:30 Q&A    
12:45 Lunch Break    
Nanoparticle Generation and Applications : Patricia Alloncle
Authors : Daniel E. Martínez-Tong1, Adriano J. García-Martín2, Tiberio A. Ezquerra3, Aurora Nogales3, Esther Rebollar2
Affiliations : Materials Physics Center (MPC). P. Manuel de Lardizábal 5, 20018 Donostia, Spain; Instituto de Química Física Rocasolano (IQFR-CSIC), Serrano 119, 28006 Madrid, Spain; Instituto de Estructura de la Materia (IEM-CSIC), Serrano 121, 28006 Madrid, Spain

Resume : Ferroelectric polymers and copolymers find applications in different fields and are candidates for versatile and cheap data storage memory devices, with easy processing for a large-scale device or for optical and piezoelectric devices. It has been previously reported that a small amount of nanoparticles (NPs) of gold, silver and silicon oxide may significantly improve the ferroelectric properties in fluoropolymers. Additionally, gold NPs may induce polymorphism in fluoropolymers and improve the resistance toward thermal degradation. Typical strategies to obtain these nanocomposites are based on solution mixing of the polymer with the NPs previously prepared. Classical strategies to obtain metallic nanoparticles are based on the chemical reduction of corresponding oxidized cations by means of suitable reactants fulfilling the twofold roles of reductant and stabilizers. One alternative approach is pulsed laser ablation in liquids (PLAL), which is a simple, versatile and cost effective technique, and it is promising for the production of impurities free NPs of diverse materials. This work reports on the preparation of ferroelectric polymer/gold nanocomposites by PLAL. For this, the gold target was immersed in different liquids, in particular, deionized water, 2-butanone, and directly in a PVDF-TrFE solution in 2-butanone. The target was ablated using a Q-switched Nd YAG with nanosecond laser pulses at 1064 nm, 532 nm and 266 nm. The morphological and optical characteristics of the as-synthesized gold NPs were then evaluated. Optical properties of gold NPs were analyzed by ultraviolet-visible absorption. The UV-Vis spectra of gold NPs disclosed the occurrence of SPR peaks in the range of 518 to 532 nm as a function of the laser wavelength and the irradiation medium. Furthermore, the dried NPs obtained by depositing the suspensions by spin coating on silicon wafers, have been examined using atomic force microscopy (AFM). Spherical NPs with sizes from around 10 to 50 nm were measured and the results from UV-VIS and AFM correlated well. A dependence of the media in which irradiation is performed is observed. Finally, the ferroelectric properties of the obtained nanocomposites are characterized by piezoresponse force microscopy.

Authors : S. Brajnicov, A. Palla-Papavlu, M. Filipescu, V. Satulu, T. Tozar, M. Dinescu
Affiliations : National Institute for Lasers, Plasma, and Radiation Physics, Atomistilor St. 409, Magurele, ZIP 077125, Romania

Resume : The fabrication of superhydrophobic polymer surfaces is of high interest both in research and industrial applications. Now, with the help of laser-based techniques, by combining surface architecture with surface chemistry it is possible to attain superhydrophobicity. In this paper we show our recent progress in obtaining superhydrophobic polymer surfaces by matrix assisted pulsed laser evaporation (MAPLE) onto different types of substrates (flexible and rigid pre-patterned). In MAPLE the Nafion fluorpolymer is suspended (1-3 %wt) in a mixture of water and ethanol at different concentrations, which is then frozen and subjected to laser irradiation in a vacuum chamber. The laser radiation is absorbed by the solvent which mechanically transports the material molecules to a substrate placed parallel with the frozen target and at a distance of several cm. The as obtained polymer coatings are chemically, morphologically, and structurally tested and their adhesive properties are evaluated. In addition, we propose an explanation for the fabrication strategy of superhydrophobic surfaces and finally, we present a potential application and draw general conclusions along this proposed guideline for designing superhydrophobic polymer coatings by MAPLE.

Authors : Scivoletto, G.(1), Bellissima, A.(1), Cucci, L.M.(1), Foti, A.(1), Fraix, A.(2), Petralia, S.(2), Giorgini, E.(3), Notarstefano, V.(3), Marzo, T.(4), La Mendola, D.(4), De Bonis, A.(5), Puglisi, A.(6), Reimhult, E.(6), Satriano, C.*(1).
Affiliations : (1) Department of Chemical Sciences, University of Catania, Italy (2) Department of Drug and Health Sciences, University of Catania, Italy (3) Department of Life and Environmental Sciences, Polytechnic University of Marche, Italy (4) Department of Pharmacy, University of Pisa, Italy (5) Department of Sciences, University of Basilicata, Italy (6) Department of NanoBiotechnology BOKU - University of Natural Resources and Life Sciences, Austria

Resume : Palladium-based nanomaterials have shown significant potential for biomedical applications because of their unique optical properties, high stability in physiological environment and excellent biocompatibility. Compared with other intensively studied noble metal nanoparticles (NPs), such as Au and Ag, Pd NPs offer higher photothermal conversion efficiency and photothermal stability, which has made them getting great attention in the field of theranostics. In this work, two approaches were followed to fabricate Pd-based nanomaterials to exploit their laser-induced photothermic response for application as multifunctional anticancer nanoplatforms. In the first approach, cisplatin (CisPt), a well-known alkylating agent already in use in clinics as chemotherapeutic, was physisorbed onto PVP-capped spherical Pd NPs. The combination of CisPt with nanoparticles offers many advantages, including increased drug solubility and half-life, enhanced therapeutic efficiency - as the small size of the NP carrier allows the drug to pass across the biological barriers- and diminished uncontrolled side effects. In the second approach, the cytotoxicity against cancer cells of Pd-based nanomaterials was scrutinized simply by the tuning of plasmonic, and therefore photothermal, properties of Pd nanorods at different aspect ratios, both in the presence and in the absence of PVP capping agent. The two systems, both spherical and cylindrical Pd NPs were characterized by UV-visible spectroscopy, to study the plasmonic features, XPS, micro-Raman and XRD, to investigate the surface chemical structure and cristallinity; DLS and Zeta-potential, to examine the hydrodynamic size and the surface charge properties, and by AFM and TEM, to assess the morphology and aspect ratio. The photothermal properties of Pd-based NPs were examined in solution following the increase of temperature under irradiation with CW laser using a FLIR C3 thermal imaging camera. Cellular experiments carried out on prostate cancer cells (PC-3 line), showed that the developed nanosystems, significantly reduced both cell migration (wound scratch assay) and cell viability, demonstrating an antitumoral activity against PC-3 cell line. Confocal microscopy and Raman Microspectroscopy cell imaging evidenced dynamic processes at the level of sub-cellular compartments and a modulation of intracellular copper ions accumulation, while xanthine oxidase assay and MitoSOX assays confirmed an increase of reactive oxygen species (ROS) generation proving the oxidative damages as a key factor for the antitumoral action induction. The financial support by MUR under Grant PRIN (project code: 2017WBZFHL) and University of Catania (PIAno di inCEntivi per la RIcerca di Ateneo 2020/2022 GRABIO_Linea di intervento 2) is acknowledged. C.S. also acknowledges the Consorzio Interuniversitario di Ricerca in Chimica dei Metalli nei Sistemi Biologici (C.I.R.C.M.S.B.), Bari, Italy.

Authors : Foti, A.*(1), Domingo, J.(2), Serrano Olmedo, J.J.(2), Ramos, M.(2), Sanfilippo, S.(1), Satriano, C.(1).
Affiliations : (1) Department of Chemical Sciences, University of Catania, Italy (2) Centre for Biomedical Technology, Polytechnic University of Madrid (UPM), Spain

Resume : The application of nanotechnology in the biomedical area is becoming more and more important for nanomedicine and theranostics. Noble metal nanoparticles (NP), specifically, exhibit enhanced optical properties depending on the particle size and shape as well as on the dielectric constant of the surrounding media, which known as surface plasmon resonance (SPR) effect. Among plasmonic NPs, gold nanorods (AuNRs) show a strong near-infrared (NIR) absorption peak, tunable by the aspect ratio of the NP, which makes them suitable for plasmonic photothermal therapy (PPTT). In this process, the photon energy generated by a laser beam is converted to thermal energy, resulting in a temperature increase and, in turn, cellular damage. Hyaluronic acid or hyaluronan (HA) is a highly biocompatible, biodegradable, and non-toxic natural polysaccharide commonly used to target tumor cells. Indeed, HA selectively binds the CD44 transmembrane glycoprotein receptor, overexpressed in several types of cancers and also associated with tumor progress and metastasis. This work focuses on the green synthesis and physicochemical / biological characterization of HA surface-capped AuNRs, to exploit the potential application for PTTT of tumors. UV-visible spectroscopy was performed to study the evolution of plasmon peak of AuNRs before and after coating with HA. The increase of the hydrodynamic diameter after the conjugation was studied with dynamic light scattering (DLS) experiments and the measurement of viscosity was investigated with a viscosimeter. The cytotoxicity response of both normal and tumor cells was investigated on fibroblast (L-929), glioblastoma (CT-2A) and melanoma (B16-F10) cells lines. In order to evaluate the receptor-dependent cellular uptake, confocal microscopy imaging was performed with bare and HA-capped AuNRs. The photothermal efficiency in inducing local hyperthermia was assessed in vitro and in vivo after the irradiation with 808 nm NIR light. The financial support by MUR under Grant PRIN (project code: 2017WBZFHL) and University of Catania (PIAno di inCEntivi per la RIcerca di Ateneo 2020/2022 GRABIO_Linea di intervento 2) is acknowledged. C.S. also acknowledges the Consorzio Interuniversitario di Ricerca in Chimica dei Metalli nei Sistemi Biologici (C.I.R.C.M.S.B.), Bari, Italy.

Authors : Redigolo, L.(1), Priolo, I.(1), Sanfilippo, V.(1), Forte, G.(2), La Mendola, D.(3), Satriano, C.*(1).
Affiliations : (1) Department of Chemical Sciences, University of Catania, Italy (2) Department of Drug and Health Sciences, University of Catania, Italy (3) Department of Pharmacy, University of Pisa, Italy

Resume : In the present work we assembled hybrid peptide-nanomaterial (p-NM) systems to scrutinize their interaction at the biointerface with model cell membranes made of supported lipid bilayers (SLBs). Peptide sequences mimicking neurotrophic factors, such as NGF (Nerve Growth Factor), BDNF (Brain Disease Neurotrophic Factor) and NT3 (NeuroTrophin 3) were immobilized by either physisorption or chemisorption on nanocomposites of gold nanoparticles and graphene oxide (Au@GO). The biophysical properties of the artificial cell membrane, before and after the interaction with p-NM systems, were investigated by in liquid atomic force microscopy (AFM), in terms of morphology, and by laser scanning confocal microscopy (LSM). In particular, the latter was utilized with the Fluorescence Recovery After Photobleaching (FRAP) and the Fluorescence Resonance Energy Transfer (FRET) techniques, to study the average molecular lateral diffusion and the electron transfer processes at the hybrid nanobiointerface, respectively. The experimental studies were paralleled by computational analyses by molecular dynamics. The financial support by MUR under Grant PRIN (project code: 2017WBZFHL) and University of Catania (PIAno di inCEntivi per la RIcerca di Ateneo 2020/2022 GRABIO_Linea di intervento 2) is acknowledged. C.S. also acknowledges the Consorzio Interuniversitario di Ricerca in Chimica dei Metalli nei Sistemi Biologici (C.I.R.C.M.S.B.), Bari, Italy.

Authors : Tomasella, P.(1), Sanfilippo, V.(1), Foti, A.(1), Fraix, A.(2), Petralia, S.*(2), Forte, G.(2), Fortuna, C.(1), Giuffrida, A.(1), Subbiahdioss, G.(3), Reimhult E.(3), Satriano C.(1).
Affiliations : (1) Department of Chemical Sciences, University of Catania, Italy (2) Department of Drug and Health Sciences, University of Catania, Italy (3) Department of NanoBiotechnology BOKU - University of Natural Resources and Life Sciences, Austria

Resume : In this study, self-cleaning and photothermally active hybrid organic-inorganic nanocomposites were developed by the assembling of thiolated reduced graphene oxide (rGOSH) and silver nanorods (AgNRs). To achieve this goal, both experimental and theoretical efforts were focused on design, synthesis, and physicochemical / biological characterization of GO-Ag hybrids. Plasmonic properties of the silver-decorated nanosheets and the actual reduction occurred concomitantly with the thiolation of GO were scrutinized by UV-visible spectroscopy (UV-VIS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and circular dichroism spectroscopy (CD). Thermogravimetric analyses (TGA), contact angle measurements, atomic force microscopy (AFM) and transmission electron microscopy (TEM) were performed in order to prove the increase in the hydrophobic character as well as the size, and preferential gathering of the silver nanoparticles onto the nanosheet substrates. The photothermal properties of GO-Ag hybrids were examined in solution following the increase of temperature under irradiation with CW laser using a FLIR C3 thermal imaging camera. Moreover, the interaction of the hybrid nanocomposites with supported lipid bilayers (SLBs), used as cell membranes model system, were studied by quartz crystal microbalance with dissipation (QCM-D) monitoring. In vitro cellular experiments by fluorescence microscopy and SEM imaging on Gram-positive S. aureus and Gram-negative P. aeruginosa showed increased dead bacteria on GO-Ag hybrids compared to control. The financial support by MUR under Grant PRIN (project code: 2017WBZFHL) and University of Catania (PIAno di inCEntivi per la RIcerca di Ateneo 2020/2022 GRABIO_Linea di intervento 2) is acknowledged. C.S. also acknowledges the Consorzio Interuniversitario di Ricerca in Chimica dei Metalli nei Sistemi Biologici (C.I.R.C.M.S.B.), Bari, Italy.

15:45 Q&A    
Poster Session : Patricia Alloncle, Palla-Papavlu Alexandra, Evgeny Gurevich, Maria Kandyla
Authors : A.Groza1, M.Serbanescu1, B.Bita1, O.Stoican1, I.G.Lupu2, R. M. Zvonaru2, O.Cramariuc3, M.Ganciu3
Affiliations : 1National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, P.O. Box MG 36, Magurele, 077125 Bucharest, Romania 2Department of Textile Products Engineering and Design, Gh. Asachi Technical University Iasi, Iași, Romania 3IT Center for Science and Technology, Bucharest, Romania

Resume : Electrospinning is a well-known technology for the fabrication of nano-sized fibers of interest in different research areas such as biomaterials, electronics, textiles, or biomedical applications [1]. The electrospinning process is generated by applying a high electrical voltage to a capillary nozzle that sprays a polymer liquid solution into the atmosphere. The liquid jet is electrically charged, ionized, and further polymerized into a fiber collected on a grounded conductive substrate foil. The distance between the nozzle and the grounded substrate as well as the applied voltage, the polymer solution concentration or solution flow rate are parameters that influence the structure and morphology of the nanofibers [2]. A melt electrospinning process is produced by concentrating a laser beam in the front of the capillary nozzle through which is atomized the polymer solution jet. Several studies [2] report the advantages of using lasers such as concentrate heating, instantaneous melting, or control over the fiber diameter. The fiber diameters decrease as the laser power energy increases. The results presented in this paper envisaged our studies regarding the effect of laser energy on the polymer nanofibers and the density of the collected fiber networks. Multiple laser beams with wavelengths ranging from ultraviolet to infrared and powers of a few hundred mW up to a few W are focused on polymer solution jet in front of the capillary nozzle. The dependence of the distribution of the nanofiber diameters on the laser beam parameters is calculated after performing high-resolution scanning electron microscopy investigations. The molecular structural modifications induced by the laser radiation on polymer fibers are studied by Fourier Transform Infrared spectroscopy. Acknowledgment: This research was supported by a grant of the Romanian Ministry of Education and Research CCCDI project number PN-III-P2-2.1-PED-2019-4021 within PNCDI III. References [1] D. H. Reneker, H. Fong, Polymeric Nanofibers, Washington, DC, USA: Amer. Chem. Soc., vol. 918, 2006. [2] B. Cramariuc, R. Cramariuc, R. Scarlet, L.R. Manea, I.G. Lupu, O. Cramariuc, Fiber diameter in electrospinning process, J. Electrostatics, 2013, 71(3), 189–198. [3] M. M. Bubakir, H. Li, A. Barhoum, W. Yang, Handbook of Nanofibers, Advances in Melt Electrospinning Technique, Springer International Publishing 2018

Authors : F. Dumitrache 1, C. Fleaca 1, I. P. Morjan 1, A. Criveanu 1, I. Lungu 1, L. Gavrila-Florescu 1, A. Tiliakos 1,2, A. Marinoiu 2, G. Prodan 3
Affiliations : 1. National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, Măgurele, , Romania. 2. National R&D Institute for Cryogenic and Isotopic Technologies (ICSI), 4 Uzinei Street, Râmnicu Vâlcea, 240050, Romania 3. “Ovidius” University of Constanta, Constanta, Mamaia Avenue 124, Romania

Resume : Iron oxide nanoparticles (NPs) has been synthesized by laser pyrolysis technique from iron pentacarbonyl vapors, ethylene and a mixture of O2 and Ar as reactive flow. Here the ethylene was used both as laser sensitizer for a foccused CO2 laser incident beam and as carrier flow for iron pentacarbonyl vapors. A parametric study regarding influence of O2 proportion in reactive mixture on the morpho-structural charactetistics of resulted NPs was made. In this study, nanoparticles with narrow size distributions and particles with about 8 to 13 nm mean diameters were obtained. In determined conditions disordered maghemite (>90% Fe3+) like nanoparticles were directely synthesized by laser pyrolysis as XRD and XPS measurements revealed. Some as prepared samples were also termaly treated at: 200, 450, 700°C for 2 hours in high vaccum, synthetic air flow or a reductive environment containing a mixture of H2/NH3 in Ar. The crystalline structures, the particle morhologyies and elemental compositions of both as synthesized and treated nanoparticles have been investigated by XRD, XPS, TEM and EDS analysis. The nanoaggregate sizes of these particles in water suspension at 0.5 g/l concentation were analysed by DLS measurements. Also the morpho-structural changes of nanoparticles during thermal treatments were identified using TGA and TEM investigations. The thermal treated samples revealed enhanced crystalinity, particle size (up to 25 nm) and the crystalline structure variyng from hematite, magnetite and maghemite.

Authors : Klemensas Laurinavičius, Sergej Orlov
Affiliations : State research institute Center for Physical Sciences and Technology

Resume : Acceleration of charged particles using vector pulsed laser beams is a field that has been gaining interest in recent years. Particularly interesting is the radially polarized beam, for which both theoretical and experimental analysis of electron dynamics has demonstrated promising results. The efficiency is caused by the fact that radially polarized beams when focused have a non-zero longitudinal electric field component. As the laser beam is focused tighter, the energy is concentrated in the longitudinal component. We introduce radially polarized chirped pulsed beams and investigate how different values of chirp, beam width, beam power and initial phase influence dynamics of a single electron. We study here chirped pulsed beams having positive and negative temporal chirp. Near the axis, the longitudinal component of these beams can be approximated by a Gaussian profile. We investigate kinetic energies and dynamics of electrons leaving the accelerating field and investigate its dependency on three main parameters: the beam waist, initial pulse phase and the temporal linear chirp. It turns out that 3 different scenarios are possible. The first one is already widely studied as the electron is propulsed in the same direction as the beam propagation. The main novel result here is our report on scenarios when the beam attracts the electron. The charged particle is effectively accelerated in the direction opposite to the direction of the beam propagation. This is enabled by proper choice of the beam width, the sign of the chirp and initial phase. Lastly, we found a situation when the electron is not accelerated by the beam. As long as the beam is present the electron becomes confined in the focal region of the pulsed chirped beam. We observe the electron being propulsed forwards or backwards with an oscillatory trajectory. Lastly, we investigate the maximal kinetic energy of the electron enabled by the introduction of the various chirp, beam width, and power values.

Authors : O.V. Kuzyk 1, I.D. Stolyarchuk 1, O.O. Dan’kiv 1, R.M. Peleshchak 1 2, A. Medvids 3
Affiliations : 1 - Drohobych Ivan Franko State Pedagogical University, Ukraine; 2 - Lviv Polytechnic National University, Ukraine; 3 - Riga Technical University, Latvia

Resume : Zinc oxide (ZnO) is a multifunctional inorganic semiconductor material with industrial applications in many fields. The ZnO has a complex system of dot defects: interstitial atoms of zinc (Zni) and oxygen (Oi), vacancies of zinc and oxygen, as well as antistructural defects. Under the influence of laser irradiation, pairs of defects are generated in both the oxygen and zinc sublattices. The defects are the centres of deformation: the interstitial atoms are the centres of deformation of stretching, and the vacancies are the centres of deformation of compression. The large values of elastic constants indicate that the deformation effects can play an important role in the modification of the near-surface layers. As a result of self-consistent deformation-diffusion redistribution of the concentration of point defects in the crystal, there is a noniniform deformation and, under certain conditions, their self-organization (the formation of nanoparticles) occur. The presence of such deformation in the semiconductor with point defects due to self-consistent electron-deformation coupling leads to the local change in the band spectrum and, accordingly, to the spatial redistribution of conduction electrons and the emergence of electrostatic potential Depending on the relationship between the individual components of the flux of defects, it is possible their localization in different areas of the crystal, or, conversely, “blurring” throughout the volume. At the first stage, due to the uneven heating of the ZnO, there is an irregular deformation field, which creates deformation-diffusion fluxes of defects. Moreover, defects that are centres of stretching (interstitial atoms) move in the region of relative stretching (to the crystal surface), and defects that are centres of compression (vacancies) move in the opposite direction. At the next stage, as a result of nonlinear interaction between defects the self-organizing processes occur. This becomes possible when the deformation flow of defects is greater than the usual diffusion flow and drift flow. An important role here is played by the value of the deformation potential and its ratio with the electrostatic potential. Since the deformation potential of interstitial atoms is much greater than that of vacancies, then at relatively low intensities of laser radiation, but greater than some critical value, the most probable situation is when the processes of self-organization of only Zni nanoparticles are possible. With increasing intensity of laser radiation, the deformation flux also becomes significant for Oi. In this stage the formation of ZnO nanoparticles as a result of self-consistent deformation-diffusion redistribution of defects is discussed.

Authors : Behnam ZeinalvandFarzin(1), DongKun Lee(2), Geun Hyeng Kim(3), Jaedu Ha(1), Jong Su Kim(1*), Yeongho Kim(4), Sang Jun Lee(4)
Affiliations : (1) Department of Physics, Yeungnam University, Gyeongsan 38541, Republic of Korea;(2) Institute of Photonic & Nano Technology, Department of Physics, Yeungnam University, Gyeongsan 38541, Republic of Korea;(3) Department of Aero Mechanical Engineering, Kyungwoon University, Gumi 13557, Republic of Korea;(4) Division of Interdisciplinary Materials Measurement Institute, Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea;* Corresponding author

Resume : In this work, the characteristic time constant of p -n and p -i-n GaAs junctions was investigated by photo-reflectance spectroscopy. Using the exponential behavior of the photo-reflectance signal, a limitation is introduced for the chopping frequency of photo-reflectance from the time constant point of view. A simple formula is used for calculating the characteristic time constants from the phase diagram of the sample. Finally, an explicit formulation is derived for the characteristic time constant of the junction. This proposed semi-empirical formulation relates the characteristic time constant to photo-voltage, excitation wavelength and intensity, permittivity, depletion width, and the most important, the quantum efficiency of the junction. Employing this formula and estimating the related parameters from the photo-reflectance spectrum, one can estimate the quantum efficiency of the junction. The formula examined for two structures: a p -n GaAs junction and a p -i-n GaAs solar cell for different excitation intensity, and the quantum efficiency of the junctions estimated by the method. The proposed method can be used as a contactless method to compare the quantum efficiencies of the junctions.

Authors : K. Andritsos a, E. Dimitriou b, M. Makrygianni a, I. Theodorakos a, A. Kaldeli-Kerou c, F. Zacharatos a*, N. Michailidis b and I. Zergioti a.
Affiliations : a. School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Iroon Polytechniou 9, 15780, Athens, Greece b. Physical Metallurgy Laboratory, Department of Mechanical Engineering, School of Engineering, Aristotle University of Thessaloniki, GR 54124 Thessaloniki, Greece c. PLiN Nanotechnology S.A., Spectra Business Center, 57001 Thessaloniki, Greece

Resume : The laser printing of metal nanoparticle inks has fostered the advancement of flexible electronics over the past 10 years. In particular, laser-induced forward transfer (LIFT) combined with laser sintering have emerged as a digital micro-fabrication technology for metallic micro-patterns for components requiring flexible form factors and low temperature processing. Silver nanoparticle inks have been the primary option for LIFT owing to their high conductivity and environmental stability, while copper, being also very conductive, can be an attractive cost-effective alternative for solution processed metal nanoinks. In this work, we investigate a non-Newtonian CuO NP ink, with rheological properties specifically designed for LIFT. In order to assess the jetting behaviour of the ink during the LIFT process, a high-speed imaging setup is coupled with the LIFT station to investigate the liquid jet’s propagation as a function of the process parameters. The latter include the laser fluence, the laser repetition rate, the donor’s layer thickness and the donor-receiver gap. Morphological characterization confirms that controllable printing of droplets is feasible from a donor layer thickness set at 30 μm and a donor-receiver gap distance set at 90μm. In addition, the printing of linear patterns is accomplished by scanning the laser beam over the donor surface at a 0.55 m/s scanning speed. As a last step, laser sintering is applied to the linear printed patterns on glass substrates to form metallic micro-patterns in ambient atmospheric conditions. The localized heating induced by the laser sintering process has been proven very effective in delivering metallic patterns with resistivity down to 5x bulk Cu. Moreover, the short duration of the laser sintering process is expected to suppress any re-oxidation, which would otherwise appear during full-scale thermal processing (e.g. oven sintering).

Authors : F. Mirabella, M. Mezera, M. Weise, M. Sahre, K. Wasmuth, A. Hertwig, J. Krüger, V.-D. Hodoroaba, J. Bonse
Affiliations : Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin, Germany

Resume : Due to its large strength-to-weight ratio and excellent biocompatibility, titanium materials are of paramount importance for medical applications, e.g. as implant material for protheses. In this work, the evolution of various types of laser-induced micro- and nanostructures emerging on titanium or titanium alloys upon irradiation by near-infrared ultrashort laser pulses (925 fs, 1030 nm) in air environment is studied for various laser fluence levels, effective number of pulses and at different pulse repetition rates (1 – 400 kHz). The morphologies of the processed surfaces were systematically characterized by optical and scanning electron microscopy (OM, SEM). Complementary white-light interference microscopy (WLIM) revealed the corresponding surface topographies. Chemical and structural changes were analysed through depth-profiling time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray diffraction (XRD) analyses. The results point towards a remarkable influence of the laser processing parameters on the surface topography, while simultaneously altering the near-surface chemistry via laser-induced oxidation effects. Consequences for medical applications are outlined.

Authors : Enrico Di Russo(1,2,3), Francesco Sgarbossa(1,2), Pierpaolo Ranieri(1), Samba Ndiaye(4), Sébastien Duguay(4), François Vurpillot(4), Lorenzo Rigutti(4), Jean-Luc Rouvière(5), Vittorio Morandi(3), Davide De Salvador(1,2), Enrico Napolitani(1,2,6).
Affiliations : (1) Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, Via Marzolo 8, 35131 Padova, Italy. (2)INFN-LNL, viale dell’Università 2, 35020, Legnaro, Padova, Italy. (3) CNR-IMM, Via Gobetti 101, Bologna, 40129, Italy. (4) Normandie Univ., UNIROUEN, INSA Rouen, CNRS, Groupe de Physique des Matériaux, 76000 Rouen, France. (5) Univ. Grenoble Alpes, CEA, IRIG-MEM, 38000 Grenoble, France. (6) CNR-IMM, Via S. Sofia 64, 95123 Catania, Italy.

Resume : Attaining Ge1-ySny alloys with high Sn content is a keystone for a large number of applications ranging from high performance nanoelectronics to integrated mid-infrared photonics in Si [1]. Here, we present a novel approach for the fabrication of fully relaxed Ge1-ySny layers on Ge with Sn fraction up to 13 % and very high crystalline quality. The incorporation of Sn in Ge was obtained by sputtering of thin Sn films (< 20 nm) directly on Ge wafers followed by laser pulsed melting that leads to the diffusion of the Sn in Ge [2]. The concentration of Sn in the alloys was varied as a function of the thickness of the Sn film and the laser process parameters (number of shots). Microstructural analyses combining high-resolution transmission electron microscopy, atom probe tomography and nanobeam precession electron diffraction were performed to investigate the Sn distribution and the strain state down to the nanoscale. Ge1-ySny layers with y > 6 % are fully-relaxed with respect to the Ge substrate, and Sn-rich regions are formed in correspondence of dislocations. With the exception of these regions, Ge1-ySny alloys present a very homogeneous and random Sn distribution, with all Sn atoms located in substitutional positions, as revealed by Rutherford back-scattering measurements. The new approach adopted in this work offers an attractive alternative to epitaxy or ion implantation to locally fabricate high quality Ge1-ySny alloys, with possible attractive developments for the production of direct bandgap Ge-based alloys by adopting strain engineering techniques. [1] S. Wirths, D. Buca, S. Mantl, Si-Ge-Sn alloys: From growth to applications, Prog. Cryst. Growth Charact. Mater. 62 (2016) 1–39. [2] C. Carraro, et al., N-type heavy doping with ultralow resistivity in Ge by Sb deposition and pulsed laser melting. Applied Surface Science 509 (2020): 145229.

Authors : Paulius Slevas, Karolis Mundrys, Sergej Orlov, Orestas Ulcinas
Affiliations : Center for Physical Sciences and Technology, Sauletekio Ave. 3, Vilnius, Lithuania; Workshop of Photonics, Mokslininku st. 6A, Vilnius, Lithuania

Resume : The most common laser beam profile is known as a Gaussian mode. It can be focused to a tiny area and therefore used in a wide range of material processing applications. However, some laser related processes can be improved by using beam shaping techniques. For instance, non-diffractive beams, such as Bessel-Gauss, Mathieu beams proved to be advantageous for transparent material laser micromachining due to their long diffraction-less focal region or elliptical elongated transverse intensity distribution. Airy beam also belongs to the family of non-diffractive beams and its main lobe has an interesting property of bending parabolically during propagation. Various techniques are used to obtain said beam, among which employment of spatial light modulator or geometric phase element is common. In both methods a calculation of a hologram is required. We demonstrate the possibility to control the beam formation position in all 3 dimensions during the design process of the mask. In this work we present a technique for Airy mask calculation which generates two Airy beams at first diffraction orders with independently controllable positions. We select the parameters to accomplish two beams overlapping which allows to create an elongated main lobe in a transverse beam profile and a constant intensity distribution on a propagation axis. We then inscribe nano-gratings inside fused silica sample to make a geometrical phase beam shaping mask. Lastly, we explore application possibilities of the mentioned Airy beams for transparent materials modification and micro processing.

Authors : Streisel, Leon(1); Ehrhardt, Martin(1,*); Lorenz, Pierre(1); Heinke, Robert(1,2); Hossain, Afaque(1); Zimmer, Klaus(1)
Affiliations : (1) Department of ultra-precision surfaces, Leibniz Institute of Surface Engineering (IOM), Permoserstraße 15, 04318 Leipzig, Germany (2) Institute of Manufacturing Science and Engineering, Technische Universitat Dresden, 01062 Dresden, Germany * corresponding author; Lead presenter: Leon Streisel

Resume : The process requirements for ultrahigh precision machining for optical surfaces are particularly high regarding low (sub)-surface defect generation, precise control of the material removal rate, and low roughness/waviness of the machined surface. It is still challenging for laser ablation-based processes to fulfil these requirements. Beam machining technologies have favorable characteristics due to the contact-less tool impact as known from ion and plasma beams. In order to qualify lasers for ultrahigh precision machining, the so-called LIPE (laser-induced plasma etching) technique was recently introduced. The LIPE based on a “free-standing” microplasma which is generated by a laser-induced optical breakdown in gases or gas mixtures near atmosphere pressure. The plasma-generated reactive species can interact with the samples surface causing a chemical reaction that finally results in etching of the material. Until now it was shown that inorganic materials like SiO2, Ge, Si can be machined by LIPE with an extremely high surface quality. Fiber reinforced composite materials like SiC-SiC can be etched without mechanical defects too but these featuring a complex surface topography due to the complex material composition. In the present paper the concept of LIPE is transferred to etching of polymer surfaces. The impact of the main etching parameters such as laser pulse energy, temperature, pressure, gas composition or plasma-surface distance to the LIPE etching of polymer surface are shown and discussed. Atomic force (AFM), optical as well as scanning electron microscopy (SEM) are applied to characterize the etched surface topography.

Authors : Jing Qian*(1)§, Colm Delaney(2)§, Xia Zhang(1), Larisa Florea(2), A. Louise Bradley(1).
Affiliations : (1)School of Physics and AMBER, Trinity College Dublin, College Green, Dublin 2, Ireland; (2)School of Chemistry and AMBER, the SFI Research Centre for Advanced Materials and BioEngineering Research, Trinity College Dublin, the University of Dublin, College Green, Dublin 2, Ireland.

Resume : Photonic crystals fabricated by direct laser writing exhibit strong potential for detecting solvent vapours of varying concentration with low fabrication cost, minimal power consumption and highly sensitive response, which make them a promising candidate as components of the sensors [1, 2]. Most examples of 2PP-fabricated high-resolution structures such as those used in 3D art painting, 3D colorful holograms, anti-counterfeiting etc. using printed by vendor-purchased photoresists [3-5]. Self-designed stimulus responsive hydrogels as 2PP printing materials show great advantages in terms of design flexibility for a range of sensing applications [2]. Herein, we report on square spiral type photonic structures showing vivid structural colors in visible spectral range. The structure is designed with Lumerical FDTD software and fabricated using a newly-designed acrylamide-based vapor responsive hydrogel with direct laser writing 2PP. A home-built transmission spectroscopy testbed is combined with a CCD camera and bubbling system to measure the zero-order responsive transmission spectrum of the photonic arrays. The temporal and spectral responses to the different vapors studied (water, ethanol, IPA, acetone) over a range of concentrations, controlled by changing the flow rate are investigated. Changes in the transmitted intensity and spectra shifts are analysed. The data shows excellent sensitivity, reproducibility and reversibility. An expansion model has also been developed to further reveal the influencing factors for the changes in the transmission colour. The experimentally tested vapor response results show this bio- and environmental-friendly material has enormous potential for vapor sensors used in connected-living devices for homes, labs, factories due to its concentration sensitivity and structural color reversibility. Furthermore, the spiral structure is extremely advantageous for fast printing. The printing speed is greatly shortened compared to the grid-type structure we reported earlier [2], which makes it suitable for printing larger area devices in a short period of time, such as flexible wearable devices or human-eye-observable sensors. References [1] C. Fenzl, T. Hirsch, O. S. Wolfbeis, Angew. Chem. Int. Ed. 13 (2014) 3318 [2] C. Delaney, J. Qian, X. Zhang, et al. J. Mater. Chem. C 9 (2021) 11674-11678 [3] H. Wang, Q. Ruan, H. Wang, S.D. Rezaei, et al, Nano Lett. 21 (2021) 4721 [4] H. Wang, H. Wang, Q. Ruan, et al. ACS Nano 15 (2021) 10185 [5] W. Zhang, H. Wang, H. Wang, et al. Nat. Commun. 112 (2021) 1

Authors : Holban, A.M.*(1,2), Joia, A. (1), Zarif, M. (3), Vizireanu, S. (3), Grumezescu, A.M.(2,4), Birca, A.(4), Farcasiu, A.T. (5), Marinescu, F. (1,2), Chifiriuc, M.C. (1,2)
Affiliations : (1)Department of Microbiology and Immunology, Faculty of Biology, University of Bucharest (2)Research Institute of the University of Bucharest, Romania (3) National Institute for Laser, Plasma and Radiation Physics, Magurele, Romania (4)Department of Science and Engineering of Oxide Materials and Nanomaterials, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest (5) Faculty of Dental Medicine, U.M.F. Carol Davila, Bucharest

Resume : Biofilm development has serious biomedical implications, from the development of microbial dental plaque, which could determine oral pathologies, to the persistent biofilm infections developed in medical devices, causing severe illness. Due to their multicellular organization, social behavior and metabolic changes, biofilm bacteria are very resistant to any known antimicrobial drug and also to the host immune system. In this study we aimed to develop and evaluate the antibiofilm activity of a plasma acting in atmospheric pressure and low temperature conditions, suitable for the inhibition and biofilm removal from various substrates, such as glass, hydroxyapatite and natural enamel. The materials were characterized by FTIR spectroscopy, SEM, TEM and SAED, while biofilm development was analyzed in a monospecific static biofilm, using a Pseudomonas aeruginosa and a Staphylococcus aureus model strain. Biofilm development was significantly inhibited in all of the analyzed substrata, in a manner dependent on the plasma exposure time and growth conditions. Furthermore, the disruption of mature biofilms was also noticed in both hydroxyapatite and natural enamel substrates when using treatments of five to ten plasma scans. The killing mechanism could be related with the generation of oxidative stress in the biofilm, but serious morphology disruption of the biofilm cells was revealed by the SEM analysis.

Authors : T. Giannakis, M. Kandyla
Affiliations : National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute,

Resume : Viscoelastic properties of stored red blood cells using single beam optical tweezers T. Giannakis, M. Kandyla Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vasileos Constantinou Avenue, 11635 Athens, Greece Optical trapping, implemented by optical tweezers, is the celebrated method of immobilizing microscopic and nanoscopic objects at the focus of a laser beam, taking advantage of the gradient force, which arises from light refraction through the object1. We can immobilize at the focus of a laser beam objects such as living cells, viruses, bacteria, organelles, DNA, etc., without physical contact, and study their basic physical and chemical properties. Optical trapping is a highly sensitive method, capable of measuring forces in the fN (10-15N) range, therefore, it can probe very small variations in biological properties. Optical tweezers are an excellent tool for the study of red blood cells (RBCs) because they can trap a single RBC at a time, image it through a built-in microscope and measure its apparent viscoelastic properties, such as its elasticity (shear elastic constant) and membrane viscosity2. Elasticity is related to the ability of RBCs to resist deformation and membrane viscosity is associated with how fast RBCs recover their original conformation after deformation. In this work, we measure simultaneously and in the same RBC membrane viscosity and elasticity using single-beam optical tweezers. The experimental procedure is repeated in several day intervals, to investigate how the storage of RBCs affects their viscoelastic properties. Our setup consists of a CW diode solid state laser beam (1064 nm) focused through a 100x oil immersion objective lens of a home-built inverted microscope, equipped with a CMOS camera, which records the images of the trapped objects in real time and, finally, captures them in a computer to be quantitatively and qualitatively analyzed. Moreover, the optical trap is equipped with a quadrant photodetector (QPD) for particle tracking. References 1. Zhu, R., Avsievich, T., Popov, A. & Meglinski, I. Optical Tweezers in Studies of Red Blood Cells. Cells 9, 545 (2020). 2. Lima, C. N. et al. Evaluating viscoelastic properties and membrane electrical charges of red blood cells with optical tweezers and cationic quantum dots – applications to β-thalassemia intermedia hemoglobinopathy. Colloids and Surfaces B: Biointerfaces 186, 110671 (2020).

Authors : F. Stanculescu(1), M. Socol(2), C. Breazu(2), G. Socol(3), G. Popescu-Pelin(2), O. Rasoga(2), G. Petre(2,1), N. Preda(2), A. M. Solonaru(4), M. Girtan(5), A. Stanculescu(2)
Affiliations : (1) University of Bucharest, Faculty of Physics, 405 Atomistilor Street, P.O. Box MG-11, Bucharest-Magurele, 077125 Romania (2) National Institute of Materials Physics, 405A Atomistilor Street, P.O. Box MG-7, Bucharest-Magurele, 077125 Romania, (3)National Institute for Laser, Plasma and Radiation Physics, Str. Atomistilor, Nr. 409, PO Box MG-36, Magurele, Bucharest, 077125, Romania (4) P. Poni Institute of Macromolecular Chemistry, 41 A Gr. Ghica Voda Alley, 700487-Iasi, Romania (5)University of Angers, Photonics Laboratory, University 2, Bd. Lavoisier 49045, Angers, France

Resume : The charge carriers transport in bi-layer organic photovoltaic (OPV) structure is affected by the reduced diffusion length of exciton and reduced donor-acceptor interfacial contact area, limitation overpassed by using as active layer blends of the two components, as bulk heterojonctions (BHJ). Fullerene, C60, is the standard acceptor for vacuum-deposited OPVs, while the more soluble derivatives are necessary for solution-deposition to assure a good homogeneity of the active layer. [6,6]-Phenyl C71 butyric acid methyl ester ([70]PCBM) is a high fullerene analog, with enhanced absorption in visible, high charge mobility and high solubility in common solvents. This paper presents some studies of the organic heterostructures realised between ITO and Al electrodes with a BHJ active layer from poly(arylenevinylene)s containing carbazole units substituted at 2,7- and 3,6- positions as donors and ([70]PCBM as acceptor blended in different weight ratio (1;1, 1:2 1:3), deposited by Matrix assisted pulsed laser evaporation (MAPLE) using a KrF* excimer laser with =248 nm, in the following experimental conditions: dichlorbenzene as solvent, fluence=300 mJ/cm2, number of pulses=10000-20000. The UV-Vis absorption and photoluminescence spectra correlated with the dark/illumination drawn I-V curves and structure/morphology from XRD, AFM, SEM were used to identify the organic heterostructure showing the best parameters, in correlation with the composition and thickness of the mixed layer.

Authors : Paulius Kizevicius, Ernestas Nacius, Rusne Ivaskeviciute-Povilauskiene, Domas Jakubauskis, Linas Minkevicius, Sergej Orlov, Gintaras Valusis, Paulius Slevas
Affiliations : State research institute Center for Physical Sciences and Technology Sauletekio ave 3, LT-10257 Vilnius, Lithuania

Resume : One of the challenges for photonics is the beam shaping - both longitudinal and transversal. The focal profile makes a huge impact on the efficiencies of processes and applications. Bessel beam has a unique beam shape because its Rayleigh length is considerably bigger when compared to a Gaussian beam. Also, its intensity peak remains unchanged during the beam propagation. This finds numerous uses for various wavelengths and various fields like communication, light-matter interaction, and imaging. As example, they help to achieve super-resolution both in optical light-sheet microscopy and THz imaging. We have employed a THz system for conversion of the Gaussian beam into Bessel beam, which is based on phase elements, fabricated by high power femtosecond laser ablation of a Si pad. We have designed and fabricated a multilevel axicon converter for 0,6 THz radiation. We study the performance of those fabricated elements. As we know the design, we numerically estimate the expected spatial intensity distribution of the THz Bessel beam using the nonparaxial diffraction theory. Moreover, we profile the surface of the element and create a numerical model for the observed aberrations. This enables us to estimate numerically the influence of the deviations from the model due to some fabrication imperfections. Lastly, we experimentally verify the performance of the laser-ablated photonic converter. We report on various benchmarks for the multilevel Si converter fabricated using high power femtosecond system.

Authors : A. Bercea, M. Filipescu, S. Brajnicov, A. Palla-Papavlu
Affiliations : National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, Atomistilor Street 409, Magurele, ZIP 077125, Romania

Resume : In recent years there has been a growing interest for two-dimensional nanomaterials such as graphene, for applications in the electronic and optoelectronic industries. Graphene has many advantages; however, its main disadvantage for application in devices remains the need to use special growth / synthesis and handling conditions. In the field of sensors, most of the research work is focused on reducing the size of the sensors and identifying and quantifying several species. Also, fast response, minimum hardware requirement, good reversibility, sensitivity and selectivity are also qualities of an excellent sensor. The main problem related to the new generation of miniaturized sensors is the complexity of the manufacturing processes, i.e. the integration of many functions on the same device through a single manufacturing process. Thus, in this work we have optimized the laser induced forward transfer process (LIFT) of two-dimensional atomic layers of graphene by applying the shadowgraphy technique. In addition, we have transferred graphene with high spatial resolution for the subsequent realization of sensors for the detection of low concentrations of ammonia.

Authors : N. Nedyalkov1*, A. Dikovska1, Ru. Nikov1, Ro. Nikov1, G. Atanasova2, M. Koleva1, L. Aleksandrov2, M. Terakawa3
Affiliations : 1Institute of Electronics, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee blvd, 1784, Sofia, Bulgaria 2Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, bld. 11, Acad. Georgi Bonchev str, 1113, Sofia, Bulgaria. 3Department of Electronics and Electrical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan

Resume : This work presents some of the main characteristics of the ablation process of silicon nitride ceramic by nanosecond laser pulses. Laser processing is performed by Nd:YAG laser system at four wavelengths – 266, 355, 532, and 1064 nm. The dependences of the ablation depth on the applied laser fluence and the pulse number for the different wavelengths are presented and discussed. It is found that the increase of the laser fluence at fixed pulse number, leads to a saturation of the ablation depth for all wavelengths used. The laser treatment also results in a variety of micro- and nanostructures on the surface of the material. Their characteristics as a function of the processing parameters are defined. The process of ablation is realized by decomposition of the ceramic, as traces of silicon are found in the processed area. The observed dependences are discussed based on a detailed analysis of the chemical and morphological changes estimated by classical analytical methods as XPS, XRD, SEM, TEM. The evolution of the decomposition process is also presented using a heat diffusion equation model.

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

Resume : This work represents results on nanosecond laser ablation of AlN and Si3N4 ceramic plates immersed in double distilled water. The radiation from a nanosecond Nd: YAG laser system operated at the fundamental (1064 nm), second (532 nm), third (355 nm), and fourth (266 nm) harmonic was used in the ablation process. The ablation rate defined as ablation depth per pulse as a function of the laser fluence and the applied pulse number is studied and discussed. The morphology of the structured ceramic surfaces and chemical changes induced by the laser radiation were also studied. The obtained results could be used in the design of method for efficient laser processing of nitride ceramics.

Authors : Lucas Duvert 1, Adrien Casanova 1, Jérôme D Robin 2, Frédérique Magdinier 2, Anne-Patricia Alloncle 1
Affiliations : 1) Aix-Marseille University, CNRS, LP3 UMR 7341, Campus de Luminy, Case 917, 13288, Marseille cedex 9, France 2) Aix-Marseille University, INSERM, MMG, Marseille Medical Genetics, 13385 Marseille, France

Resume : Laser-induced forward transfer (LIFT) is a versatile, non-contact, high-resolution laser direct writing technique that offers promising solutions in various fields of application. Our work is focused on the use of this technique to build organized 2D/3D arrangements of biomaterials and living cells to create in vitro biomodels for tissue engineering or regenerative medicine. LIFT is a two-part printing method using laser-matter interaction to transfer tiny amounts of material from a thin donor film to a receptor substrate, both separated by a few hundreds of micrometres. A short laser pulse induces the formation of a jet propagating perpendicularly to the donor substrate. The bio-ink previously spread as a thin film on this donor substrate is thus collected as a micrometer-sized droplet on the receiver. In order to precisely control the amount and the location of the deposited material, it is necessary to investigate carefully the jetting dynamics as a function of various parameters including the laser fluence and the rheological properties of the bioink. In this study, we used time-resolved fast imaging to investigate the hydrodynamics of the transfer of successive jets at high pulse repetition rate. The set up being currently used is composed of a high-frequency laser (12ps, 60KHz) coupled with a fast-writing scanner that allows us to print large quantities of materials in extremely short times. Successive pulses are focused on a bioink-coated donor substrate and the transfer material is imaged with a shadowgraphic technique using a delayed nanosecond flash. With this technique, we can record precise moments of the dynamics and accurately decompose the ejection mechanism. We present here our investigations on the jet dynamics as a function of the rheological properties of the bioink, the irradiation fluence, the distance and time between each individual jet… Understanding and controlling these dynamics will allow us to improve the quality and reproducibility of the prints. It will also help us to estimate the ideal donor-receiver distance in order to minimize the mechanical impact of the deposition process on the cells contained in the bio-ink.

Authors : M. Socol1*, N. Preda1**, A. Costas1, C. Breazu1, G. Petre1,2, A. Stanculescu1, G. Popescu-Pelin3, A. Stochioiu2,3, G. Socol3
Affiliations : 1National Institute of Material Physics, 405A Atomistilor Street, 077125, Magurele, Romania 2University of Bucharest, Faculty of Physics, 405 Atomistilor Street, PO Box MG-11, 077125, Magurele, Romania 3National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, 077125, Magurele, Romania

Resume : In the last years, many attempts have been carried out in order to develop new materials and architectures for fabricating flexible and lightweight photovoltaic cells. Organic semiconductors have features like low processing temperatures, high absorption coefficients, mechanical flexibility, compatibility with plastic (even on large area) substrates) that make them suitable for the integration in the organic photovoltaic devices. Inorganic nanostructures are characterized by good electronic properties, high intrinsic charge carrier mobility and thermal stability. Thus, hybrid photovoltaic (HPV) cells can be developed by embedding inorganic nanoparticles in an organic active layer, these cells combining the properties of both organic and inorganic components. In this study, hybrid composite thin films based on poly(3-hexylthiophene) (P3HT), [3,9-bis(2-methylene-(3-(1,1- dicyanomethylene)-indanone))-5,5,11,11-tetrakis 4-hexylphenyl) -dithieno[2,3-d:2,3-d]-s-indaceno[1,2-b:5,6-b]dithiophene] (ITIC) and ZnO nanoparticles were deposited by matrix assisted pulsed laser evaporation (MAPLE). The obtained hybrid organic:inorganic thin films were characterized by complementary techniques (XRD, FTIR, SEM, EDX, AFM, UV-Vis, PL and I-V measurements) in order to assess the influence of the ZnO concentration on their morphological, structural, optical and electrical properties. The work proves that MAPLE can be regarded as a viable approach for depositing hybrid composite thin films, which further can be used in the development of solar cells.

Authors : M. Filipescu*, A. Palla-Papavlu, V. Ion, A. I. Radu, C. Craciun, A. Bonciu, M. Dinescu
Affiliations : National Institute for Lasers, Plasma and Radiation Physics, 077125 Magurele, Romania

Resume : Permanent, rigorous and efficient monitoring of the environmental pollution involves the use of efficient devices, namely highly sensitive and reproducible sensors that work at room temperature. The most important part of such a sensor is the active membrane that detects these pollutants, based on chemical or physical phenomena. In the case of chemoresistive sensors, the use of new composite material obtained by mixing organic and inorganic compounds appears to be a promising alternative. Polyaniline (PANI) mixed with tungsten oxide nanoparticles is a composite material which can be used in sensors applications due to high specific surface area and capability to convert chemical interactions into electrical signals. Thin films of this composite were obtained by matrix assisted pulsed laser evaporation technique. A frozen target consisting in a mixture of polyaniline, WO3 nanoparticles (different concentrations) and toluene solvent was irradiated with a Nd:YAG laser working at 266 nm wavelength. The surface morphology was in detail studied by atomic force microscopy and scanning electron microscopy and the chemical bonding was investigated by Fourier transformed infrared spectroscopy. The PANI/ WO3 ratio influence on the electrical properties was also studied. Acknowledgement: This work was supported by a grant of the Ministry of Research, Innovation and Digitization, CNCS - UEFISCDI, project number PN-III-P1-1.1-TE-2021-0219 (CO-POLYSENS), within PNCDI III and the Romanian National Nucleus Program

Authors : S.A.Yehia1,2, L.Carpen1,2, F. Stokker-Cheregi1, C. Porosnicu1, V.Satulu1, C.Staicu1,2, B.Butoi1, A. Bercea1, A. Palla-Papavlu1, G.Dinescu1,2
Affiliations : 1National Institute for Lasers, Plasma and Radiation Physics, 77125, Magurele – Bucharest, Romania 2Faculty of Physics, University of Bucharest, 77125, Magurele – Bucharest, Romania

Resume : The study of Be nanoparticle (NP) synthesis is very important within the framework of the next fusion reactors such as the International Thermonuclear Experimental Reactor facility (ITER). This interest is two-fold, i.e., Be dust is expected to be produced in large quantities at ITER, and, Be dust is toxic. Thus, the synthesis of Be NPs in a controlled environment is a great opportunity to expand our knowledge onto these dusts. In this work we investigate different laser parameters, Be target composition, and the liquid environment in which laser ablation occurs in order to investigate the NPs formation. We found that Be NPs with variable sizes can be synthesized by applying 532 and 1064 nm laser wavelengths. In addition, the chemical analysis of the NPs reveals that Be is their main constituent. The samples obtained in heavy water are rich in metallic Be (66%). Finally, Be NPs synthesized in heavy water lead to the incorporation of D in the material, with a D:Be ratio of 2.5:1000. Acknowledgement: This work has been carried out within the framework of the INFLPR Nucleus Programme and the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 EUROfusion). Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them.

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LIPSS I : Evgeny Gurevich
Authors : Johannes Heitz, Gerda Buchberger, Cristina Plamadeala, Martina Muck, Werner Baumgartner, Achim Walter Hassel, Dominik Knapic
Affiliations : Institutes of Applied Physics, of Biomedical Mechatronics, and for Chemical Technology of Inorganic Materials, Johannes Kepler University Linz, Austria

Resume : Bio-inspired micro- and nanopatterning of materials by means of laser radiation is a rapidly growing field to tailor special industrial, medical, and scientific applications. This is significantly driven by the exciting properties of micro- and nanopatterned materials found in natural biological species, including pronounced adhesive and anti-adhesive properties, wetting and directional fluid transport, and control of cell growth. The structuring techniques addressed here focus on developments in laser processing using short and ultrashort laser pulses. This includes the self-organized formation of micro- and nanopatterns at surfaces induced by exposure to laser radiation as well as direct writing techniques such as two-photon polymerization. Acknowledgement: This study was funded by the European Union’s Horizon 2020 research and innovation programme under the agreements No. 862016 (BioCombs4Nanofibers) and No. 951730 (LaserImplant).

Authors : W. Karim1, A. Petit1, M. Tabbal2, A.L. Thomann1 and N. Semmar1
Affiliations : 1 GREMI-UMR 7344-CNRS-University of Orleans, 14 rue d’Issoudun, 45071 Orleans Cedex2, France 2 Department of Physics, American University of Beirut, Beirut, Lebanon 1107 2020.

Resume : The interaction between ultrashort laser beam pulses with a material can induce the formation of periodic surface micro/nano structures commonly referred to as LIPSS (Laser Induced Periodic Surface Structures). Controlling such a process can pave the way for the tuning of the physico-chemical properties of the material’s surface. In the case of electrochemical cells made of assembly of thin films incorporating Gadolinium-Doped Ceria (GDC), LIPSS formation can enhance the performance of the electrode by increasing its surface area and thus enhancing the reactions of the active species at the electrode/electrolyte interface. In this work, a Nd: YAG laser beam operating at the third harmonic (355 nm) and emitting 40 ps laser pulses is employed to irradiate a 4x4 mm2 surface of a GDC thin layer, that is deposited by magnetron sputtering on yttria-stabilized zirconia (YSZ) substrate. Using high resolution scanning electron microscopy (HR-SEM), it is found that LIPSS are produced at a low fluence laser multi-pulse regime close to the ablation threshold. In agreement with the literature, it is found that these periodic structures can be distinguished depending on their spatial period and can be classified as low and high spatial frequency LIPSS, LSFL and HSFL, respectively. However, under the static mode (irradiation of the same area of 500 µm diameter) and under appropriate values of laser fluence (50 to 250 mJ/cm2) with a number of pulses varying from 1 to 70, we have also identified two types of LSFLs that are distinct in their direction and spatial period. LSFL#1 are parallel to the beam polarization, with a typical period of 238 nm and found in the center of the irradiated zone, whereas LSFL#2 are oriented perpendicular to beam polarization with a spatial period of 296 nm and found on the rim of the irradiated zone. Our results suggest that the appearance of the two types of LSFL within the irradiated spot can be attributed to different metallic and dielectric behaviors of the inner and outer zones of the GDC film, respectively. These differences are attributed to increased oxygen losses under the higher beam intensity region. We have also optimized the process parameters to generate well resolved LIPSS under beam scanning conditions. Using numerical tools for SEM/AFM images and thanks to a simple geometric model developed on such structures, the enhancement of the specific surface following laser structuring is estimated to be in the range from 50 to 80%.

Authors : A.M. Richter (1), G. Buchberger (2), D. Stifter (3), J. Duchoslav (3), A. Hertwig (1), J. Bonse (1), J. Heitz (2), K. Schwibbert* (1)
Affiliations : (1) Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin, Germany (2) Institute of Applied Physics, Johannes Kepler University Linz, Austria (3) Center for Surface and Nanoanalytics, Johannes Kepler University Linz, Austria * lead presenter

Resume : Using nanofiber-like cell appendages, secreted proteins and sugars, bacteria can establish initial surface contact followed by irreversible adhesion and the formation of multicellular biofilms. Here, the stabilizing extracellular biofilm matrix together with physiological changes on the single cell level leads to an increased resilience towards harsh environmental conditions, antimicrobials, the host immune response and established cleaning procedures. Persistent microbial adhesion on e.g., medical implants, in water supply networks or food-processing industry is often associated with chronic inflammation, nosocomial and foodborne infections, enhanced biofouling and product contamination. To prevent persistent microbial colonization, antibacterial surface strategies often target the initial steps of biofilm formation and impede adhesion of single cells before a mature biofilm is being formed. While chemical coatings have been widely used, their restricted biocompatibility for eukaryotic cells and attenuated antibacterial-effects due to compound release limit their areas of application and alternative strategies focus on modified surfaces topographies to impede bacterial adhesion. In this work, we used ns-UV laser treatment (wavelength 248 nm and a pulse duration of 20 ns) to generate laser-induced periodic surface structures (LIPSS) with different submicrometric periods ranging from ~210 to ~610 nm on commercial poly(ethylene terephthalate) (PET) foils. Following structurally and chemically analyses, PET samples were subjected to bacterial colonization studies with Escherichia coli TG1, a bacterial test strain with a strong biofilm formation capacity due to the formation of nanofiber-like cell-appendages (pili). Bacterial adhesion tests revealed that E. coli repellence decisively depends on the spatial periods of the LIPSS with the strongest reduction (~91%) in cell adhesion observed for LIPSS periods of 214 nm. Scanning electron microscopy and additional biofilm studies using a pili-deficient E. coli TG1 strain revealed the importance of extracellular appendages in the bacterial repellence observed here, thus, pointing out new antibiotics-free strategies for antibacterial surfaces by impeding nanofiber-mediated bacterial adhesion.

Authors : Javier Prada-Rodrigo (1 2), Jijil JJ Nivas (3), Meilin Hu (3), Marcella Salvatore (3), Stefano Oscurato (3), Salvatore Amoruso (3), Tiberio A. Ezquerra (4), Pablo Moreno (1), Esther Rebollar (2)
Affiliations : 1 Grupo de Aplicaciones del Láser y Fotónica (ALF-USAL), Universidad de Salamanca, Pl. de la Merced s/n, 37008 Salamanca, Spain; 2 Instituto de Química Física Rocasolano (IQFR-CSIC), C/Serrano 119, 28006 Madrid, Spain; 3 Dipartimento di Fisica "Ettore Pancini", Università degli Studi di Napoli “Federico II” Complesso Universitario di Monte S. Angelo Via Cintia I-80126 Napoli (Italy); 4 Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Científicas (IEM-CSIC), Serrano 121, 28006 Madrid, Spain

Resume : We present a study on the formation of Laser Induced Periodic Surface Structures (LIPSS), by means of nanosecond laser vector beams, at a wavelength of 532nm, on the surface of thin films of either a conductive polymer: poly(3-hexylthiophene) (P3HT) or a fullerene derivative: [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) deposited over n-silicon (1 0 0) doped with arsenic. These materials have raised interest in the field of organic electronics and photovoltaics due to their electronic properties, the possibility of thin film preparation and their optical absorption in the visible range. Previous studies [1,2] in both materials have shown the possibility of forming LIPSS using standard beams. The electrical conductivity of these structures is higher in the valleys of LIPSS as compared to the peaks. In this work, we try to extend these investigations by using vector beams. The vector beams were generated using a commercially available vortex half-wave plate which, when irradiated with linearly polarized light, transforms it into a vector beam with radial, azimuthal, or spiral polarization depending on the angle between the polarization vector of the input beam and the fast axis of the plate. The topographical changes of the samples after irradiation were studied by confocal microscopy in order to check the orientation of the LIPSS and by Atomic Force Microscopy (AFM) to characterize both their period and depth. Regarding the conductivity of the samples, it is measured by Conducting AFM (C-AFM). We were able to generate LIPSS, which appear parallel to the polarization of the beam, that is radial, concentrical or spiral. They appear after irradiation from 1200 to 4800 pulses, in a fluence from 11 to 36 mJ/cm2 for P3HT and from 17 to 19 mJ/cm2 for PC71BM. Periods around 500 nm and 360 nm and depths of 120 nm and 85 nm are observed for P3HT for PC71BM respectively. In summary, by following a single step top-down approach we were capable of generating concentrical, radial and spiral periodical structures by using nanosecond laser vector beams in thin films of PH3T and PC71BM. [1] A. Rodríguez-Rodríguez, E. Rebollar, M. Soccio, T.A. Ezquerra, D.R. Rueda, J.V. Garcia-Ramos, M. Castillejo, M.C. Garcia-Gutierrez. Macromolecules 2015, 48, 12, 4024–4031. [2] E. Gutiérrez-Fernández, A.Rodríguez-Rodríguez, M.C. García-Gutiérrez, A. Nogales, T.A. Ezquerra, E. Rebollar. Applied Surface Science 2019, (476), 668-675.

Authors : M. Hu (1), J. JJ Nivas (1,2), M. Valadan (1), R. Fittipaldi (3), A. Vecchione (3), R. Bruzzese (1,2), C. Altucci (4), and S. Amoruso (1,2)
Affiliations : (1) Dipartimento di Fisica “Ettore Pancini”, Università di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli, Italy; (2) CNR-SPIN, UOS Napoli, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli, Italy; (3) CNR-SPIN, UOS Salerno, Via Giovanni Paolo II 132, I-84084 Fisciano, Italy; (4) Dipartimento di Scienze biomediche avanzate, Università di Napoli Federico II, Via Pansini 5, 80131 Napoli, Italy

Resume : We report on the process of laser surface structuring with a sequence of femtosecond laser pulses for repetition rates varying from 0.01 to 200 kHz. The investigation is carried out both in vacuum and in air by irradiating a crystalline (100) silicon (intrinsic - resistivity > 200 Ω cm - thickness ≈400 μm) target in static conditions. The sequence with a fixed number of pulses N is provided by a diode pumped CPA Yb:KGW system. The wavelength and duration of the laser pulses are ≈1030 nm and ≈180 fs, respectively. The sequence of N laser pulses at a given repetition rate is selected by using a pulse picker acting as pulse divider, while the system runs at 200 kHz. This operational mode allows keeping constant, within their typical statistical fluctuations, the features of the output laser beam during the whole experiment, meanwhile limiting the maximum laser pulse energy at the value achievable at 200 kHz. Both the threshold fluence for shallow crater formation on the irradiated target surface and the morphological features of the surface structures produced inside the crater were analyzed as a function of the repetition rate, for a fixed sequence of N laser pulses. Our experimental findings evidence an interesting variation of the threshold fluence between vacuum and air irradiation above 10 kHz, suggesting a change in the laser-target energy coupling at the higher repetition rates. This observation is ascribed to a plume shielding effect occurring at higher repetition rates in air but negligible in vacuum. In addition, there seems to be a complete absence of heat accumulation. We also observe that the threshold fluence in air is three times lower than vacuum. Such an effect is associate to the diverse efficiency of nanoparticulate debris coverage of the target surface due to material back-deposition in air with respect to vacuum. As for the features of the surface structures, our experimental findings show that the ripples period is independent of the repetition rate over the investigated range of 0.01-200 kHz. However, ripples with a larger period are formed in vacuum, an aspect ascribed to both the different modulation of the surface depth and nanoparticles coverage in the two different experimental conditions. Instead, irradiation in vacuum hampers the formation of grooves, an intriguing aspect that suggests a possible role of nanoparticles debris in their formation mechanisms. All the aspects illustrated above are particularly important in view of industrial laser surface processing requiring target irradiation at high repetition rates.

10:30 Q&A    
10:45 Coffee Break    
Authors : J. Bonse (1), C. Florian (1,2), M. Mezera (1), K. Wasmuth (1), A.M. Richter (1), K. Schwibbert (1), J. Krüger (1), F.A. Müller (3), S. Gräf (3)
Affiliations : (1) Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin, Germany; (2) Princeton University, USA; (3) Friedrich-Schiller-Universität Jena, Germany

Resume : The processing of laser-induced periodic surface structures (LIPSS) represents a simple and robust way for the nanostructuring of solids that allows creating a wide range of surface functionalities featuring applications in optics, tribology, medicine, energy technologies, etc. While the currently available laser and scanner technology already allows surface processing rates at the m2/min level, industrial applications of LIPSS are sometimes hampered by the complex interplay between the nanoscale surface topography and the specific surface chemistry. This typically manifests in difficulties to control the processing of LIPSS and in limitations to ensure the long-term stability of the created surface functions. This presentation aims to identify some unsolved scientific problems related to LIPSS, discusses the pending technological limitations, and sketches the current state of theoretical modelling. Hereby, it is intended to stimulate further research and developments in the field of LIPSS for overcoming these limitations and for supporting the transfer of the LIPSS technology into industry.

Authors : E. Stratakis
Affiliations : Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology (FORTH), Greece

Resume : The fabrication of artificial biomimetic surfaces via femtosecond laser processing is presented. Metallic, semiconductor and dielectric surfaces were irradiated and Laser Induced Surface Structures (LIPSS) were observed in each type of material. In particular, femtosecond laser pulses with linear, circular, radial or azimuthal polarization states were used for structuring steel, silicon and fused silica surfaces. Experimental results showed that the direction of LIPSS in each case proved to be dependent on the laser beam polarisation. A complete study was carried out for the investigation of LIPSS dependence on fluence and the number of pulses per spot for variable beam polarization states and irradiation strategies, allowing the production of new and more complex surface structures. Furthermore, we present a novel way to control and modulate the different LIPSS morphologies and geometries. Moreover, large area surfaces were fabricated, tailored with various micro-and/or nano- structures bearing great structural resemblance to surfaces found in nature such as the lotus leaf, shark skin and butterfly Greta Oto wing. Those bioinspired surfaces manifest remarkable optical and wetting properties, which were attributed to the specific surface morphology. Thus, femtosecond laser processing can be a novel and one single-step method for the fabrication of functional surfaces on almost all classes of solid materials.

Authors : Jijil JJ Nivas (1,2), Meilin Hu (1), Rosalba Fittipaldi (3), Antonio Vecchione (3), Riccardo Bruzzese (1,2), and Salvatore Amoruso (1,2)
Affiliations : (1) Dipartimento di Fisica “Ettore Pancini”, Università di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli, Italy; (2) CNR-SPIN, UOS Napoli, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli, Italy; (3) CNR-SPIN, UOS Salerno, Via Giovanni Paolo II 132, I-84084 Fisciano, Italy.

Resume : Topological insulators are interesting materials both for their peculiar properties when reduced at low dimension and as thermoelectric materials. Investigation on the effects of irradiation of topological insulator with femtosecond laser pulses is particularly interesting to exploit the possibilities offered by laser patterning and direct writing approaches for the modification of target surface and development of functional materials. However, this topic remains still scarcely investigated. Here we report on the process of femtosecond laser irradiation and surface structuring of a crystal of bismuth telluride (Bi2Te3) with different sequences of N laser pulses (1≤ N ≤1000) at different pulse energies Ep (3 J < Ep < 60 J). The sequence of N laser pulses was generated by a Ti:Sa femtosecond laser source providing 800 nm pulse with a duration of about 35 fs at a repetition rate of 100 Hz. The laser beam was focused on the target surface, at normal incidence in air, by means of a plano-convex lens with a nominal focal length of 75 mm. The target was a piece of Bi2Te3 cleaved from a single crystal grown in a floating zone image furnace. The sample was held on a XYZ translation stage and different spots were produced by changing the laser energy and the number of pulses. The corresponding morphological features of the target surface were analyzed by using a field emission scanning electron microscope (FE-SEM). We analyzed the threshold fluence for the formation of shallow ablation crater ensuing the irradiation of the target surface. Interestingly, the shallow crater is decorated with laser induced periodic surface structures (LIPSS) on the peripheral region or in the tail of the gaussian spot but does not present the development of any surface feature in the central region of the spot irradiated by the higher energy part of the beam. Such an aspect of peculiar crater formation on the values of laser fluence and number of pulses are investigated. Remarkably, at the best of our knowledge, the formation of femtosecond LIPSS on a topological insulator material is reported for the first time. Interestingly, the presence of a two-dimensional array of periodic bumps is evidenced outside the main crater in a region when irradiated with high number of pulses at much lower values of the local laser fluence. In addition, we will also discuss the effects of the number of laser pulses, pulse energy and laser polarization on the morphological features of irradiated target surface. The possible effects of material phase change or surface oxidation on irradiation with femtosecond pulses are also considered to find the correlation with the annular shaped crater formation in Bi2Te3.

12:30 Q&A    
12:45 Lunch Break    
13:45 Plenary I    
14:45 Coffee Break    
LIFT : Palla-Papavlu Alexandra
Authors : Gert-willem Römer, Justinas Mikšys, Matthias Feinaeugle, Gari Arutinov
Affiliations : Gert-willem Römer: Chair of Laser Processing, Department of Mechanics of Solids, Surfaces & Systems, Faculty of Engineering Technology, University of Twente, Drienerlolaan 5, 7522NB Enschede, The Netherlands; Justinas Mikšys: Chair of Laser Processing, Department of Mechanics of Solids, Surfaces & Systems, Faculty of Engineering Technology, University of Twente, Drienerlolaan 5, 7522NB Enschede, The Netherlands AND Holst Centre/TNO, High Tech Campus 31, 5656AE Eindhoven, The Netherlands Gari Arutinov: Holst Centre/TNO, High Tech Campus 31, 5656AE Eindhoven, The Netherlands

Resume : Laser-induced Forward Transfer (LIFT) is an additive manufacturing technique, in which short laser pulses (typically fs, ps or ns) are employed to deposit donor material onto a substrate (receiver). In this technique, the donor material is coated on the bottom of a substrate (carrier), which is transparent to the wavelength of the laser beam. Upon absorption of the laser energy by the donor, at the carrier-donor interface, a small volume of the donor material is transferred to the receiver. Silver particle-based (AgNP) inks are widely used as conductive material in the field of printed electronics. LIFT of these inks has been successfully demonstrated. Unfortunately, the processing window is narrow, due to the non-Newtonian behavior of these inks. That is, small variations of the processing parameters can lead to undesirable effects like turbulent jets, off-angle ejection, satellite depositions etc. Therefore, fundamental understanding of the physical phenomena and dynamics, which drive the ejection of AgNP inks, is needed to improve the robustness of LIFT. This is needed to increase the robustness of the process, the “cleanliness” of deposits, as well as to reduce the volume of the depositions—i.e. to increase deposition resolution. We present the results of an experimental study in which the effect of the main laser parameters (laser pulse energy, pulse duration, laser spot diameter, donor layer thickness and the distance between the donor layer and the receiver) on the size of the AgNP ink depositions is assessed. The diameter of the smallest reproducible deposit was about 40 um, which was obtained at a spot diameter of 10 um, a donor layer thickness of 3 um and at a distance between the donor and the receiver of 13 um. Next, we employed time-resolved shadowgraphy imaging of jets, in order to study the dynamics of the jet formation during the ejection of the donor. In this study, the focus position of the laser beam was varied w.r.t. carrier-donor interface at a fixed pulse energy. This effectively implies a variation of the laser spot size and fluence level at the interface. This allowed us to study a jet-on-jet ejection mechanism, which was observed when comparing the jet formation induced by ns pulses to ps pulses. That is, a smaller secondary jet was found to form on top of the “common” main, larger jet; hence the naming jet-on-jet. The formation of the smaller jet is attributed to the formation of plasma at the carrier-donor interface. As this smaller jet has the potential to result in smaller depositions, we studied the application of two laser beams during LIFT to trigger jet-on-jet. This (also) has the potential to increase the processing window of LIFT of AgNP inks. It was found that, when the two laser spots are coaxially aligned, also a jet-on-jet forms. And that, the resolution of the deposits was maintained, as compared to a single beam, but at the same time the donor-receiver distance for successful printing was increased.

Authors : A. Casanova 1, L. Duvert 1, J. D. Robin 2, F. Magdinier 2, P. Delaporte 1, A. P. Alloncle 1
Affiliations : 1 Aix-Marseille University, CNRS, LP3 UMR 7341, Campus de Luminy, Case 917, 13288, Marseille cedex 9, France 2 Aix-Marseille University, INSERM, MMG, Marseille Medical Genetics, 13385 Marseille, France

Resume : Printing techniques applied to biology have begun to develop since the 2000s and hold great promise in a near future. They are based on interdisciplinary approaches and use a combination of cells, chemistry, engineering and sophisticated protocols to create artificial tissues. In that scope, it has been more than a decade since Laser-Induced Forward Transfer (LIFT) is studied in lab scale for its ability to print biomaterials and more specifically living cells [1], [2]. This method uses a short laser pulse to transfer tiny amounts of material from a thin film donor to a receptor substrate. Under appropriate conditions, the pulse induces the formation of a jet propagating perpendicularly to the donor substrate. The targeted material is then deposited as a droplet on the collector. It is a nozzle free printing technique, and it is considered as a suitable method to print three dimensional cellular structures with a very high spatial resolution. Combined with stem cells technology this innovative printing process opens new perspectives for the creation of complex bio-models strongly mimicking the in-vivo environment with numerous applications ranging from regenerative medicine to pharmaceutic study and drugs screening. However, the optimization of its performance and its use with living cells require a deep understanding of the ejection dynamic depending on several laser parameters (laser fluence, repetition rate, laser spot size, laser wavelength, pulse duration, absorption mechanism…) and of the effects of living cells on the bio-ink printability. At LP3 (Marseille-France) and in close collaboration with MMG (Marseille-France), we took advantages of our expertise in LIFT process [3] to master the printing by LIFT of living cells in good condition (high spatial resolution, high printing resolution and high cellular viability after printing). Here, we will present the LIFT process and its optimization allowing to master the bio-ink deposition in order to create reliable ordered patterns of bio-ink micro-droplets containing stem cells with a high spatial resolution. By changing the film concentration in cells and the laser pulse energy, we can control the droplet size and the number of cells in each droplet (from tens of cells down to the single cell level). Then, we will present a viability study of the printed cells after transfer to prove the ability of this process to create relevant bio-models. [1] J. A. Barron, et al. , « Biological laser printing of three dimensional cellular structures », Appl. Phys. A, vol. 79, no 4‑6, p. 1027‑1030, sept. 2004. [2] M. Duocastella et al., « Study of the laser-induced forward transfer of liquids for laser bioprinting », Appl. Surf. Sci., vol. 253, no 19, p. 7855‑7859, juill. 2007. [3] P. Delaporte et A.P. Alloncle, «Laser-induced forward transfer: A high resolution additive manufacturing technology », Opt. Laser Technol., vol. 78, p. 33‑41, avr. 2016.

Authors : Matthias Domke, Sandra Stroj, Justus Landsiedel, Noemí Aguiló-Aguayo
Affiliations : Research Center for Microtechnology, Vorarlberg University of Applied Sciences, Hochschulstr. 1, 6850 Dornbirn, Austria; Research Center for Microtechnology, Vorarlberg University of Applied Sciences, Hochschulstr. 1, 6850 Dornbirn, Austria; Research Institute of Textile Chemistry and Textile Physics, University of Innsbruck, Hoechstersstrasse 73, 6850 Dornbirn, Austria; Research Institute of Textile Chemistry and Textile Physics, University of Innsbruck, Hoechstersstrasse 73, 6850 Dornbirn, Austria;

Resume : A strategy to achieve high-resolution µm-sized conductive tracks without sintering temperatures is to implement laser technologies. We present here a laser-induced forward transfer process (LIFT) to transfer metallic particles on textiles. The process was optimized (1) to be applied on different types of porous and rough substrates, such as woven and knitted fabrics, and (2) to deposit silver and copper nanoparticles on localized areas of the fabrics. The deposited particles are used afterwards as seeds for the generation of copper conductive lines on fabrics via electroless copper deposition. Here we discuss the laser parameters and mechanisms of the LIFT process required for the generation of metallic nanoparticles on fabrics, as well as optimizations on the LIFT process for the formation of localized conductive lines via electroless deposition.

Authors : K. Andritsos a, I. Theodorakos a, F. Zacharatos a, A. Kabla b, S. Melamed b, F. de la Vega b, Y. Porte c, P. Too c and I. Zergioti a
Affiliations : a. School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Iroon Polytechniou 9, 15780, Athens, Greece b. PV Nano Cell Ltd., 8 Hamasger st., P.O. Box 236 Migdal Ha’Emek, Migdal Haemek 2310102, Israel; c. FlexEnable Ltd, 34 Cambridge Science Park, Cambridge, CB4 0FX, United Kingdom

Resume : The laser digital processing of metal nanoparticle inks has contributed significantly to the rapid advancement of flexible electronics over the past 10 years. Despite these advancements in processing, many challenges related to complex surface morphologies, non – planar form factors and multi-material interfaces with diversified thermal and optical properties, remain unmet. In this work, we explore the boundaries of conformal laser processing of Ag nanoparticle inks employing the laser induced forward transfer (LIFT) technique, for micro-patterns formed on particularly sensitive substrates and multilayered structures within an OTFT architecture. The laser sintering process parameters are tuned so as to minimize the damage induced on the neighboring interfaces. The latter involve challenging surface morphologies, such as patterns and micro-components with periodicity and aspect ratio in the nano to 100-micron scale. We investigate the effect of a plethora of essential for the laser sintering technique parameters, such as the laser repetition rate, the laser pulse duration, the pulse to pulse spatial and temporal overlap and the laser wavelength to the overall result of the process. Thorough characterization comprising optical microscopy, profilometry and SEM observation sheds light to the heat affected zone of the substrates, as well as the morphology and structure of the laser sintered patterns. The electrical performance of the laser printed and sintered patterns is assessed by means of electrical measurements in a 4-point probe IV station. The demonstrated results validate the versatility and flexibility of LIFT combined with laser sintering, which can offer a digital solution to particularly challenging use cases and applications in flexible electronics, in particular for OTFTs for the next generation of flexible displays.

Authors : Voicu, S.I.*(1, 2), Pandele, A.M.(1, 2), Oprea, M.(1, 2) & Tuncel, C.(2).
Affiliations : (1)Advanced Polymers Materials Group, Gheorghe Polizu 1-7. 011061 Bucharest, Romania (2)Faculty of Chemical Engineering and Biotechnologies, University Politehnica of Bucharest, Gheorghe Polizu 1-7. 011061 Bucharest, Romania

Resume : Increased selectivity, response speed, and sensitivity in the chemical and biological determinations of gases and liquids are arguably an important step towards future micro and nano sized sensing systems. This work surveys our latest progress in engineered complex materials, i.e. graphene functionalized with monoclonal antibody anti-alpha-fetoprotein, for applications as recognizing elements in miniaturized surface acoustic wave sensor design and application. Graphene functionalized with monoclonal antibody anti-alpha-fetoprotein have been printed by laser induced forward transfer (LIFT) into 2-dimensional pixels onto the active surface of a SAW platform. First, a parametric study (i.e. laser fluence, donor film morphology and thickness as well as single versus multiple pixel deposition) was carried out to determine the optimum experimental conditions under which sensitive pixels are obtained. Following the morphological and structural characterization of the laser printed material, the responses of the coated SAW resonators are measured. The sensitivity of the monoclonal antibody anti-alpha-fetoprotein functionalized graphene coated SAW devices gives an indication these devices represent an enabling technology for monitoring liver damage. The obtained sensor showed a good signal for detection of AFP in range 1,2-145,1 micro g/L with potential application in early detection of liver cancer forms. Acknowledgements: This work was supported by a grant of the Ministry of Education and Research, CNCS UEFISCDI, project number PN-III-P2-2.1-PED-2019-1603 “Surface acoustic wave biosensor based on functionalized graphene with monoclonal anti-alpha-fetoprotein antibody for hepatic cancer diagnostic” within PNCDI III.

16:30 Q&A    
Start atSubject View AllNum.
Ultrashort laser processing : Evgeny Gurevich
Authors : Petru Ghenuche
Affiliations : Extreme Light Infrastructure - Nuclear Physics (ELI-NP), Horia Hulubei" National Institute for Physics and Nuclear Engineering (IFIN-HH)

Resume : Months before the first experiments using a 10 PW laser at ELI-NP, we explore the avenues opened by this unprecedented level of light-mater interaction. Already at the edge of material science technology, the complex laser and experimental architecture poses numerous challenges on critical aspects of laser-based acceleration, diagnostic and control of the laser-plasma interaction. We will present our strategies to generate spatially and temporally landscaped electromagnetic fields for acceleration of particles and applications. Not only they will enhance the performance of the most powerful laser in the world, but it will also impact the acceleration mechanisms if coupled with a careful target design. We are already in an age where the desired particle beam properties are saturating with laser intensity. New designs and technologies will help scaling laws to reach the extreme level of intensities and pressures required for new physics and applications ranging from radiation generation to advanced QED experiments.

Authors : Tony Hajj 1.4 Djamila Bouaziz1,2,4 Assia Guessoum2 Gregoire Chabrol 1,3 Nacer-E. Demagh 2 Sylvain Lecler 1,4
Affiliations : 1ICube, UMR 7357, Université de Strasbourg-CNRS, 67 412 Illkirch, France 2Laboratoire d’Optique Appliquée, IOPM, Ferhat Abbas University, 19 000 Setif, Algeria 3ECAM Strasbourg-Europe, 67 300 Schiltigheim, France 4INSA de Strasbourg, 67 000 Strasbourg, France

Resume : Laser marking has gained a lot of interest in the past two decades for anti-counterfeiting applications, such as medicinal product identification [1]. To improve the writing resolution, UV femtosecond laser can be used: Concentrating the energy in time makes it possible to benefit from athermal multiphoton absorption to achieve smaller ablation. However, these lasers are still expensive. An alternative method is to concentrate the energy in space using a Bessel beam [2] or photonic nanojet [3]. A photonic nanojet is a highly focused beam at a mesoscale of a dielectric object. Optical fiber tips are a good candidate to achieve photonic nanojet for laser marking applications. The main limitation was the difficulty to fabricate single-mode optical fiber-shaped tips with high curvature. Throughout the years, various fiber micro-lens fabrication techniques have been developed such as laser or electric arc heating processes, wet etching, micro-bead splicing, mechanical polishing, etc. A method, we have recently developed, using polymer-based techniques, offers a low cost and ease fabrication of Hemi-aspherical micro-lenses with high curvatures that cover only the fiber core. Such micro-lenses are the best for light focusing especially for single-mode fibers. In addition, the flexibility of the polymer-based techniques [4], gives precise control over the shape and size of the micro-lens without putting any stress on the fiber. With our technique, a variety of polymers are suitable for the fabrication of fiber micro-lenses such as PDMS, NOA, SU8, etc. Although a lot of information about these polymers is readily available, for instance, the refractive index, ablation fluence thresholds, operating temperature [5], the possibility to use them as microlens for high power applications is not known. Our work aims to study the focusing behavior or the change in the focal spot intensity as a function of the laser fluence, exposure time, and micro-lens temperature. For that we use a direct imaging technique of the focused beam [6], to monitor the potential changes in light cartography generated by the micro-lens. The study will also be accompanied by thermodynamic simulations carried out on COMSOL Multiphysics. The power range of application of these lenses is determined as a function of the polymer choice. High power laser writing application is demonstrated. [1] Krisztina Ludasi et al. “Anti-counterfeiting protection, personalized medicines − Development of 2D identification methods using laser technology”, International Journal of Pharmaceutics, vol. 605, no. 10, 120793, 2021, [2] R. Stoian, MK. Bhuyan, G. Zhang, G. Cheng, R. Meyer, F. Courvoisier, "Ultrafast Bessel beams: advanced tools for laser materials processing”, Adv. Opt. Technol. 7, 165–174 (2018). [3] R. Pierron, J. Zelgowski, P. Pfeiffer, J. Fontaine, and S. Lecler, “Photonic jet: key role of injection for etchings with a shaped optical fiber tip,” Opt. Lett. 42, 1–3 (2017). [4] M. Zaboub et al., ”Fabrication of polymer microlenses on single-mode optical fibers for light coupling”, Optics Communications, vol. 366, pp. 122–126, 2016, doi: 10.1016/j.optcom.2015.12.010. [5] N. E. Stankova et al., “Optical properties of polydimethylsiloxane (PDMS) during nanosecond laser processing,” Applied Surface Science, vol. 374, pp. 96–103, Jun. 2016, doi: 10.1016/j.apsusc.2015.10.016. [6] D. Bouaziz et al., “Direct imaging of a photonic jet at shaped fiber tips,” Opt. Lett., vol. 46, no. 20, p. 5125, 2021, doi: 10.1364/ol.435867.

Authors : Ruyue. Que1, Ludivine Houel-Renault2, Mebarek Temagoult3, Matthieu Lancry1, Bertrand Poumellec1
Affiliations : 1. Institut de Chimie Moléculaire et des Matériaux d'Orsay - ICMMO, Université Paris-Saclay 2. Institut des Sciences Moléculaires d'Orsay - ISMO, Université Paris-Saclay 3. Institute of Integrative Biology of the Cell - I2BC, Université Paris-Saclay

Resume : Smart terminals, wearable devices and increasingly integrated sensors and analysers on chips or in fibres are requiring smaller and smaller optical components. Therefore, finding suitable methods and materials for implementing photonic functions at the microscale, has always been a direction for researchers to explore. In our research, we focus on the generation of luminescence properties, as this is an important part of optical devices, especially in the display field, sensors, labelling or data storage. Luminescent organic molecules with less than eight conjugated double bond structures can usually only be excited by UV light. Their application is limited, due to the tendency of UV light to alter the properties of other neighbouring molecules. Thus, luminescent materials that can be excited by visible light, such as quantum dots (QDs), nanoparticles (NPs), dyes, etc., have been considered for fabrication or insertion into solids (or fibres), but are not easy to design in three dimensions. We discovered that direct fs laser writing (DLW) in a new type of cyclo olefin polymer (Zeonex® glass) fulfils these requirements. The process through multiphoton absorption with an infrared femtosecond laser makes it possible to perform flexible three-dimensional transformation inside transparent materials. Recently, Kallepalli et al. created luminescence in other more complex polymers (in PMMA), showing data storage applications. However, Zeonex has several advantages over PMMA, especially a low water absorption, interesting for biological applications. On the other hand, water absorption changes the refractive index to a large extent, which restricts application as an optical substrate. On the contrary, Zeonex has good performance in both fields. Zeonex is thus widely used in the fields of optics, life sciences and electronics. It is used in lens and display, however, it hasn’t been considered as a substrate for photonics. In our study, we demonstrate that using a femtosecond laser with a dedicated parameter range, guided by analytical thermal models, luminescence can be induced in Zeonex glass. The luminescent volume is localized at the focus (ca. a few micron3) of the laser beam and a few microns away from it according to laser parameters, as the thermal condition induced by the laser pulse energy seems to define the effect. On the other hand, by regulating the pulse frequency (repetition rate, RR) and pulse energy (Ep), thermal effects are controllable. We found that at least 2 luminophores are created with all luminescence in the visible range between 500 and 585 nm. These luminophores show different ratios depending on the laser parameters and positioning. For instance, with low power irradiation (Ep=100nJ, RR=200kHz), luminescence spectroscopy, located at the beam focus, shows 2 created luminophores: one(L1) is excited at 476nm and the other(L2) is excited at 510nm, they emit light at 530nm and 580nm, respectively. With higher power irradiation (Ep=100nJ, RR=500kHz), L1 is still presents, but L2/L1 ratio is larger, especially in the region a few microns away from the focus. Interpretation was discussed based on a 2-level system (S0, S1). The luminescence at these wavelengths (green-yellow) is very attractive. Besides that, we are even more excited by the fact that DLW can efficiently create new functions in organic material locally, although the mechanism needs to be further investigated.

Authors : Ščajev, P. *(1), Miasojedovas, A. (1), Mekys, A. (1)
Affiliations : (1) Institute of Photonics and Nanotechnology, Vilnius University, Saulėtekio Ave. 3, LT 10257 Vilnius, Lithuania

Resume : Photoluminescence decay characterization in solar cells and light emitting diodes by time-resolved photoluminescence is of high importance for material quality and operation speed aspects. Conventional photoelectron streak cameras are very costly due to a very complicated and specialized production process in vacuum. That indicates, that a cost-efficient and simple streak camera suitable for such tests would be highly demanded. In this presentation, a quadrupole electro-optic deflecting device is presented to be extended to full functionality streak camera operating in wide spectral range (200-1600 nm) by using electro-optic DKDP crystal. The experimental setup consisted of a laser with 10 picosecond pulse duration for sample excitation, electro-optic deflector with high voltage switch and imaging spectrograph with silicon and InGaAs cameras. This device allows spectral and temporal imaging of time-resolved luminescence dynamics in semiconductor materials, with variable bandgap and composition. The device achieves temporal resolution up to 100 ps and further can be improved by using faster high voltage switches. The research was supported by the Research Council of Lithuania under the project No. S-MIP-19-34, LT 2020 536A.

Authors : W. Chen1, P. Roelli1, H. Hu2, S. Verlekar1, S. P. Amirtharaj1, A. I. Barreda3, T. J. Kippenberg1, M. Kovylina4, E. Verhagen5, A. Martínez4, C. Galland1
Affiliations : 1. Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland 2. Hubei Key Laboratory of Optical Information and Pattern Recognition,Wuhan Institute of Technology, Wuhan 430205, China 3. Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University Jena, Albert-Einstein-Str. 15, 07745 Jena, Germany 4. Nanophotonics Technology Center, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain 5. Center for Nanophotonics, AMOLF, Science Park 104, 1098 XG Amsterdam, Netherlands

Resume : Coupling molecules or nanomaterials to plasmonic nanocavities with extreme light confinement allows for largely boosted light-matter interaction at the nanoscale and can reveal atomic-scale dynamics affecting the local optical response. Recently, building on the theory of molecular cavity optomechanics, it has been proposed that surface-enhanced Raman scattering (SERS) and infrared absorption (SEIRA) of molecules could be coherently linked to realize THz frequency upconversion toward the single-photon level in nanoscale pixels, opening new possibilities for spectroscopy, imaging, and sensing. Here, we develop a plasmonic nanoparticle-in-groove nanocavity coupled with a few hundred molecules and demonstrate optomechanical transduction of sub-microwatt continuous wave signals from the mid-infrared (32 THz) onto the visible domain (~400 THz) at ambient conditions. To achieve that, both IR and visible plasmonic modes (with electric field enhancement >100) are tightly confined in the ~1-nm-thick BPT molecular monolayer, with a target molecule vibration mode of 1080 cm-1 that are both active for IR absorption and Raman scattering. The incoming IR field resonantly drives the collective molecular vibration via SEIRA, which is probed by a visible pump laser via parametrically enhanced sum- and difference-frequency generation, and results in upconverted SERS signal on both the anti-Stokes and Stokes bands, respectively. High-resolution Raman spectra show sub-natural linewidth of the upconverted signals with respect to their underlying broad spontaneous Raman emissions (Fig. 2D, E), suggesting the coherent nature of the frequency upconversion process with a measured detection limit down to a few nW μW-2. Our dual resonant nanocavity offers an estimated 13 orders of magnitude enhancement in upconversion efficiency per molecule, which gives the external and internal IR-to-VIS photon conversion efficiency to be on the order of 10−7/W and 10-1/W of pump power, respectively. Our results establish molecular cavity optomechanics as a new paradigm for coherent frequency conversion free of phase-matching constraints.

Authors : Pietro Battocchio, Jacopo Terragni, Vito Cristino, Nicola Bazzanella, Riccardo Checchetto, Michele Orlandi, Stefano Caramori, Antonio Miotello
Affiliations : University of Trento, Department of Physics, via Sommarive 14, 38123, Trento, Italy; University of Trento, Department of Physics, via Sommarive 14, 38123, Trento, Italy; University of Ferrara, Department of Chemistry, via Luigi Borsari 46, 44121, Ferrara,Italy University of Trento, Department of Physics, via Sommarive 14, 38123, Trento, Italy; University of Trento, Department of Physics, via Sommarive 14, 38123, Trento, Italy; University of Trento, Department of Physics, via Sommarive 14, 38123, Trento, Italy; University of Ferrara, Department of Chemistry, via Luigi Borsari 46, 44121, Ferrara,Italy University of Trento, Department of Physics, via Sommarive 14, 38123, Trento, Italy;

Resume : The well known phenomenon of laser ablation recently attracted interest also in space applications as possible propulsion technique for micro and nano satellites, whose number in earth orbit is rapidly increasing. During laser ablation a small quantity of mass leaves the irradiated surface with very high exhaust velocity, so that a recoil impulse of the order of μN s is generated on the target material. In order to exploit this potential application of laser ablation it becomes then of fundamental importance the of connection between thermodynamic and optical properties of the target and the efficiency in generating the impulse to optimize fuel materials. Polymers are generally considered to be good candidates for laser ablation propulsion, with respect to metals, thanks to their lower mass density and lower ablation threshold. Among commercially available polymers poly(vinyl chloride) (PVC) shows interesting impulse generation performances[1]. However because of its low absorption it also owns poor ablation efficiency. A commonly used technique to increase polymer absorption consists in doping it with an absorber, that can be another polymer, a dye molecule, or nanoparticles. In this work impulse generated by PVC doped with carbon nanoparticles (CNP) and by PVC blended with poly(styrene-sulfonate) (PSS) is compared, by using a specifically designed ballistic pendulum[2]. Optical and thermodynamical characterizations of these materials allowed to show that the localized absorption of laser radiation by CNP results in a more efficient laser-material interaction for the generation of a mechanical impulse[3]. [1] Urech, L., et al. "Polymer ablation: From fundamentals of polymer design to laser plasma thruster." Applied Surface Science 253.15 (2007): 6409-6415. [2] Battocchio, P., et al. "Ballistic measurements of laser ablation generated impulse." Measurement Science and Technology 32.1 (2021): 015901. [3] Battocchio, P., et al. “Poly(vinyl chloride) Coupling with UV Laser Radiation: Comparison between Polymer Absorbers and Nanoparticles to Increase Efficiency for Laser Ablation Propulsion.” J. Phys. Chem. C 2021, 125, 51, 28088–28099

10:45 Q&A    
11:00 Coffee Break    
Ultrashort laser processing: Theory and applications : Evgeny Gurevich
Authors : Nadezhda M. Bulgakova, Thibault J.-Y. Derrien, Alexander V. Bulgakov
Affiliations : HiLASE Centre, Institute of Physics of the Czech Academy of Sciences, Dolní Břežany, Czech Republic

Resume : Laser processing of material surfaces is one of the key technologies for state-of-the-art applications in micro- and nanoelectronics, photonics, sensing technologies, photovoltaics, and in other fields. Silicon as one of the most abundant materials whose importance in scientific and industrial applications is not diminishing with time. Laser treatment of this material is a complicated phenomenon, which proceeds through triggering of a wealth of linear and nonlinear, thermal and nonthermal processes. Many numerical models have been developed targeting on prediction of optimal regimes of silicon laser processing. However, most of the models are usually limited to an only laser wavelength or one pulse duration with the use of a number of fitting parameters and their direct application for other laser irradiation parameters often does not provide agreement with experimental data. In this report, we will analyze the processes involved in silicon excitation and heating by ultrashort laser pulses at 1030 nm wavelength. This involves single- and multiphoton absorption, avalanche ionization, free electron recombination, dynamic optical response of the excited surface layer, melting threshold and melting dynamics at over-threshold laser fluences. The results of analysis will be directly compared with experimental data on the ablation thresholds and crater depths obtained by using a PHAROS laser (Light Conversion, 1030 nm) at pulse durations of 260 fs and 7 ps. A critical assessment is given of the concepts of plasma screening in Auger recombination [1], electron density dependence of energy coupling to the lattice [2], applicability of the multi-layer reflectivity model [3,4], ambipolar diffusion [5-7], and two-photon absorption coefficient as an effective value for several nonlinear absorption processes [7,8]. The Time Dependent Density Functional Theory (TDDTF) [9] is involved to directly derive the rate of the photo-stimulated transition through the direct Si band gap that accounts for the band gap evolution during irradiation. Finally, a set of Si parameters is outlined, which yields a good agreement between modeling and experimental data for 1030 nm, a wavelength widely used for material processing. [1] J. Bok and M. Combescot, Phys. Rev. Lett. 47, 1564 (1981). [2] T. Sjodin, H. Petek, and H-L. Dai, Phys. Rev. Lett. 81, 5664 (1998). [3] K. Sokolowski-Tinten and D. von der Linde, Phys. Rev. B 61, 2643 (2000). [4] N.M. Bulgakova, R. Stoian, A. Rosenfeld, I.V. Hertel, and E.E.B. Campbell, Phys. Rev. B 69, 054102 (2004). [5] A. Rämer, O. Osmani, and B. Rethfeld, J. Appl. Phys. 116, 053508 (2014). [6] Tao Feng, Gong Chen, Hainian Han, and Jie Qiao, Micromachines 13,14 (2022). [7] H.M. van Driel, Phys. Rev. B 35, 8166 (1987). [8] A.D. Bristow, N. Rotenberg, and H.M. van Driel, Appl. Phys. Lett. 90, 191104 (2007). [9] T.J.-Y. Derrien, N. Tancogne-Dejean, V.P. Zhukov, H. Appel, A. Rubio, and N.M. Bulgakova, Phys. Rev. B 104, L241201 (2021).

Authors : G. Calogero [1], D. Raciti [1], P. Acosta-Alba [2], F. Cristiano [3], I. Deretzis [1], G. Fisicaro [1], K. Huet [4], S. Kerdilès [2], A. Sciuto [1,5], A. La Magna [1]
Affiliations : [1] CNR-IMM, Zona Industriale VIII Strada 5, 95121 Catania, Italy [2] Université Grenoble Alpes, CEA-LETI, 38000 Grenoble, France [3] LAAS, CNRS and Université de Toulouse, 7av. Du Col. Roche, 31400 Toulouse, France [4] Laser Systems & Solutions of Europe (LASSE), 145 rue des Caboeufs, 92230 Gennevilliers, France [5] Dipartimento di Fisica e Astronomia, Università di Catania, Via Santa Sofia 64, 95125 Catania, Italy

Resume : Heating and melting solid materials over small space- and time-scales is a way to access the early stages of the melting phenomenon. Nanosecond-pulse laser annealing (LA) is a powerful processing tool for both fundamental investigations of molten phase ultra-rapid kinetics and technological applications, such as nanoscale reshaping, alloy fraction and defects manipulation, dopant redistribution and activation, which are crucial for the fabrication of unconventional 3D sequentially integrated devices. LA processes need to be developed concurrently with the device design, optimizing topography and materials’ choices in complex 3D structures of nm-sized elements with different shapes and phases. This requires a faithful modelling of the non-equilibrium melting phenomena occurring during LA at the nanoscale, which is beyond the capabilities of state-of-the-art TCAD continuum models massively used in industrial environments. In this contribution we will present a multiscale atomistic approach to model ultrafast nanoscale phase-changes during LA processes, based on seamlessly coupling a continuum, finite-elements model (FEM) for laser-matter electromagnetic interaction and thermal diffusion over the µm-scale with a superlattice Kinetic Monte Carlo (KMC) scheme, able to model with local atomic resolution the highly crystal-orientation dependent evolution of liquid-solid interfaces [G. Calogero et al, npj Comp. Mater., in press (2022)]. The methodology reproduces the local melt region in the KMC superlattice via mapping of the thermal field and evolving solid-liquid regions back and forth from FEM to KMC solvers, with nanosecond and atomic resolution and for the whole duration of the laser pulse. Implementing the thermal problem via the FEniCS toolkit and the sLKMC model via the MulSKIPS code [], this tool is fully open-source and its formalism can be applied to any system where the atom kinetics is determined by a strongly space- and time-dependent field, such as temperature or strain. In particular we will present benchmarks against phase-field models and experimental data which validate the approach, and show the results of simulated LA processes of a Si(001) surface at various laser fluences and pulse shapes, considering both homogeneous and inhomogeneous nucleation mechanisms, revealing how liquid Si nuclei generate, deform and coalesce during laser irradiation. This work was funded by EU-Horizon 2020 grant No. 871813 (MUNDFAB).

Authors : A. Fernandez Garcia (1)*, F. Agulló-Rueda (2), P. Sopeña (3), D. Grojo (3) , M. Manso Silvan (1,4), M. Garcia-Lechuga (1,4)
Affiliations : (1)Departamento de Física Aplicada, Universidad Autónoma de Madrid, 28049, Madrid, Spain; (2)Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas (ICMM-CSIC), 28049, Madrid, Spain; (3) Aix-Marseille Université, CNRS, LP3, UMR7341, 13009 Marseille, France; (4)Centro de Microanálisis de Materiales, Universidad Autónoma de Madrid, 28049, Madrid, Spain

Resume : The structure of 2D materials, characterized by presenting strong bonds with neighbouring atoms in one plane and weak interactions out of that plane, gives rise to attractive functional properties. Most of the advanced applications of these materials require the control of their monolayer/multilayer configurations, the stoichiometry of the compounds or the preferential growth in an out-of-plane orientation. In this work we study the transforming effect, both compositional and morphological, of ultrashort laser pulses on thin films of 2D materials. The objective, besides studying the laser-matter interaction in 2D materials, is to demonstrate the versatility of laser irradiation as a post-synthesis process to improve or locally change the thin-film properties. Specifically, we study the transformation of a WTe2 thin-film under irradiation with 200-fs pulses, exploring the influence of the laser wavelength (1030 nm and 258 nm), the irradiation fluence and the number of pulses by processing single-shot spots, lines, and areas. The WTe2 thin-films were fabricated by a mixed synthesis process of chemical nucleation and vapor phase transformation, forming randomly oriented 2D out-of-plane flakes over a silicon substrate. Both pre- and post-irradiated thin films have been characterized by various techniques, notably by scanning electron microscopy and micro-Raman spectroscopy. Irradiating at 1030-nm wavelength, with peak fluences in the range of 30 to 200 mJ/cm2 (fluence threshold for single-shot estimated at about 50 mJ/cm2), a decomposition of WTe2 is observed. It is evidenced by a greater presence of crystalline Te and the appearance of a higher concentration of WO3 in the resulting films. Morphologically, when scanning a large area, the formation of periodic structures (LIPSS-like) interestingly occurs. This structuring confers an anisotropy in the optical and electrical properties that can be beneficial for the applications. However, a drawback is a fusion-resolidification process that tend to eliminate the originally 2D out-of-plane flakes for the tested conditions. On the other side, by irradiating at 258-nm wavelength, under peak fluences in the range of 20 to 80 mJ/cm2 (fluence threshold for single-shot modification estimated at about 25 mJ/cm2), a very different transformation is produced. From the morphological point of view, the film undergoes nano-pores formation because of a possible selective ablation process, but without forming any periodic structure and without destroying the 2D flakes. Micro-Raman spectroscopy confirms the permanence of WTe2, the partial removal or amorphization processes of Te and the disappearance of WO3. These transformations are shown to be achievable in large area processing (scanning procedures), enhancing the interest of ultraviolet ultrashort laser pulses as a post-synthesis treatment.

Authors : Andrea Teuber1, Giada Caniglia1, Michael Wild2, Matthias Godejohann3, Christine Kranz1, Boris Mizaikoff1,4*
Affiliations : 1 Institute of Analytical and Bioanalytical Chemistry, University of Ulm, Ulm, Germany; 2 Diamond Materials, Freiburg, Germany; 3 MG Optical Solutions GmbH, Utting/Ammersee, Germany; 4 Hahn-Schickard, Ulm, Germany

Resume : Commercially available Fourier transform infrared (FTIR) spectroscopic devices are well-established in a wide range of application scenarios such as environmental monitoring and (bio)chemical analysis. However, FTIR-based techniques are limited in sensitivity. A hallmark of IR laser spectroscopy is the significantly higher energy density, albeit within a narrower spectral region. Yet, if this emission band overlaps with analyte signatures of interest, a viable alternative for IR spectroscopic analysis with high sensitivity is provided. IR lasers are also of particular interest for analyses in aqueous media, as water itself is a strong absorber in the mid-infrared (MIR) regime. Hence, a higher energy density allows for probing even highly opaque matrices. Quantum cascade lasers (QCL) can be tailored to any specific emission wavelength in the MIR regime, and if several lasers are combined a broad spectral range (> 1,000 cm-1) may be covered [1,2]. For efficiently analyzing opaque samples in attenuated total reflection (i.e., evanescent field absorption) mode, next to the laser light source appropriate MIR waveguides are required matching the emission characteristics of QCLs. If the thickness and geometrical dimensions of the waveguide are on the order of the magnitude of the wavelength of the propagating radiation, a uniform evanescent field is generated maximizing the radiation intensity within that leaking-out radiation leading to maximizing the achievable signal-to-noise (SNR) ratio [3,4]. Diamond is a promising candidate for such thin-film MIR waveguides, as it is transparent across a wide MIR band, chemically inert, and maybe be grown as nanocrystalline diamond (NCD) thin-film waveguides with micrometers thickness suitable for MIR chem/biosensing platforms [5]. In this contribution, we present a novel NCD thin-film waveguide coupled with tunable quantum cascade lasers for the detection and quantification of caffeine in real-world samples. A critical comparison between the caffeine spectra recorded using this sensor technology vs. conventional IR-ATR analysis using FTIR technology will be presented. 1. Teuber, A.; Mizaikoff, B. Cascade Laser Infrared Spectroscopy. In Encyclopedia of Analytical Chemistry; Wiley, 2021; pp. 1–45. 2. Haas, J.; Catalán, E.V.; Piron, P.; Karlsson, M.; Mizaikoff, B. Infrared spectroscopy based on broadly tunable quantum cascade lasers and polycrystalline diamond waveguides. Analyst 2018, 143, 5112–5119, doi:10.1039/c8an00919h. 3. López-Lorente, Á.I.; Karlsson, M.; Österlund, L.; Mizaikoff, B. Diamond Waveguides for Infrared Spectroscopy and Sensing. In Carbon-Based Nanosensor Technology; Kranz, C., Ed.; Springer International Publishing: Cham, 2019; pp. 87–117 ISBN 978-3-030-11864-8. 4. Haas, J.; Catalán, E.V.; Piron, P.; Nikolajeff, F.; Österlund, L.; Karlsson, M.; Mizaikoff, B. Polycrystalline Diamond Thin-Film Waveguides for Mid-Infrared Evanescent Field Sensors. ACS Omega 2018, 3, 6190–6198, doi:10.1021/acsomega.8b00623. 5. López-Lorente, Á.I.; Wang, P.; Sieger, M.; Vargas Catalan, E.; Karlsson, M.; Nikolajeff, F.; Österlund, L.; Mizaikoff, B. Mid-infrared thin-film diamond waveguides combined with tunable quantum cascade lasers for analyzing the secondary structure of proteins. Phys. Status Solidi Appl. Mater. Sci. 2016, 213, 2117–2123, doi:10.1002/pssa.201600134.

12:30 Q&A    
12:45 Lunch Break    
13:45 Plenary II    
14:45 Coffee Break    
Laser surface structuring and direct writing : Patricia Alloncle
Authors : Tobias Voss
Affiliations : Institute of Semiconductor Technology and Laboratory for Emerging Nanometrology LENA, Technische Universität Braunschweig, Braunschweig, Germany

Resume : The design of optoelectronic and photonic components based on the InGaN/GaN/AlGaN material system requires a detailed knowledge of the linear and nonlinear optical material properties. In particular for higher light intensities in lasers or high-power LED structures, nonlinear optical effects become increasingly important as the light is guided and amplified in micron- or even sub-micron sized waveguide structures. In this contribution, we will discuss second- and third-order optical effects in GaN and AlxGa1-xN thin films under excitation with femtosecond laser pulses. In particular, we analyze the impact of the Al concentration and the n-type doping level on the two-photon absorption coefficient and determine the two-photon absorption coefficient and the nonlinear index of refraction of GaN for the wavelength range of 550nm – 1550nm. We will also present investigations of the recombination dynamics of photo-excited electron hole-pairs in different GaN-based 3D heterostructures used in nano-LEDs. From the luminescence transients, we extract information about the interplay of radiative and non-radiative recombination processes as well as the screening of internal electric fields. We also demonstrate electroluminescence from hybrid LEDs based on the InGaN/GaN material system where the hole-conductive polymer PEDOT replaces the p-doped GaN layer and part of the sample structuring is performed using a femtosecond laser system.

Authors : Massimo Zimbone #, Enrico Napolitani $ , Maria Cantarella #, Vittorio Privitera §, Giuliana Impellizzeri #
Affiliations : # CNR-IMM, Via S. Sofia 64, 95123 Catania, Italy $ Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, Via Marzolo 8, 35131 Padova, Italy § CNR-IMM, Z.I. VIII Strada 5, 95121Catania, Italy

Resume : Titanium dioxide (TiO2) is actually a reference standard material for photocatalysis. It is potentially able to reduce the problem of environmental pollution in water and in air that are considered among the major humanity issues and it can be also used for the sterilization of surfaces. Indeed irradiation of TiO2 can induce the formation of electron-holes couples with a high oxidation power that oxidize the organic compounds and destroy bacteria and viruses eventually present on its surface.The deposition of good quality crystalline TiO2 on polymers can boost the use of this material in a large plethora of applications. This work reports an innovative method to obtain anatase TiO2 films on polymeric substrates (polyethylene naphthalate, PEN, and polymethyl metacrylate, PMMA). We firstly used a Low Temperature (90 °C) Atomic Layer Deposition (LT-ALD) of amorphous TiO2 on polymeric substrate and afterward, we induced a phase transition from amorphous to crystalline anatase by UV-Pulsed Laser Irradiation. A KrF excimer laser with a low penetration length was used to avoid the heating and damaging of the polymeric substrates. A detailed morphological, structural, and chemical characterization was performed and the diffusion of the heat and the temperature behavior into the TiO2 and polymeric substrates were also simulated and discussed. The effect of the laser fluence and pulse number on the amorphous-crystal transition was deeply investigated. We found that the formation of TiO2 crystals needs: 1) the fluence overcomes a threshold of ~ 45 mJ/cm2; 2) the number of pulses is higher than 10. Moreover, to avoid the formation of TiO2 cracks or degradation of the substrates, both the fluence and the number of pulses must be kept lower than 70 mJ/cm2 and 100 pulses, respectively. The photocatalytic aptitude and self-cleaning properties of the investigated films were demonstrated by the degradation of the methylene blue dye in aqueous solution and by the wettability measurements, respectively. Thus, the matching of the extremely low-temperature growth by ALD with the UV-laser irradiation allows to synthetize anatase TiO2 films on flexible substrates that could open the way to applications in photocatalysis for wastewater treatment and self-cleaning coatings.

Authors : Yogita Maithani, B. R. Mehta, J. P. Singh
Affiliations : Department of Physics, Indian Institute of Technology-Delhi, Hauz Khas, New Delhi 110016, India

Resume : Biopotential signals are used to measure organ function and diagnose diseases. Biopotential electrodes serve as an interface between the biological tissue and the electronic circuit in order to measure and record biopotentials. Wearable health-monitoring systems should be easy to use, free of stigma, and capable of providing high-quality data. Wearable textile electrodes for biopotential sensing are a promising candidate for long-term health monitoring. Smart textiles, which incorporate electronic elements directly into the fabric, offer a seamless way to incorporate sensors into garments for a variety of purposes. This paper describes the direct writing of laser-induced graphene (LIG) on a Kevlar textile for the production of reusable dry electrodes for long-term ECG monitoring. The electrode as-prepared has a high electrical conductivity and skin contact impedance of 100 ± 1 kΩ to 7.9 ± 2.7 kΩ for frequencies ranging from 40 Hz to 1 kHz, which is comparable to conventional Ag/AgCl wet electrodes. The results show comparable performance with significantly lower electrode-skin impedance for clinical-quality. Even after several hours of use, these electrodes cause no skin irritation and work effectively without the need for skin preparation. The proposed dry electrodes are expected to give greater comfort for use over time due to their flexible nature and a better match to the skin's modulus. The fabrication method is simple, cost-effective, and scalable, thus permitting the production of arbitrary-shaped flexible electrodes for long-term biopotential monitoring.

Authors : Heinke, Robert (1,2,*); Ehrhardt, Martin(2); Bauer, Jens(2); Lotnyk, Andriy(2); Lorenz, Pierre(2); Morgenstern, Roy(3); Lampke, Thomas(3); Arnold, Thomas(1,2); Zimmer, Klaus(2)
Affiliations : (1) Institute of Manufacturing Science and Engineering, Technische Universitat Dresden, 01062 Dresden, Germany (2) Department of ultra-precision surfaces, Leibniz Institute of Surface Engineering (IOM), Permoserstraße 15, 04318 Leipzig, Germany (3) Materials and Surface Engineering Group, Technische Universität Chemnitz, 09107 Chemnitz, Germany * lead presenter and corresponding author;

Resume : The precise surface machining of silicon by pulsed laser processing is challenging. Laser ablation enables direct patterning but causes various morphological as well as structural modifications of the surface and sub-surface region due to highly dynamic processes at the surface that occur also at ultrashort pulsed laser ablation. Due to the increasing demand of precisely structured silicon surface in various fields, such as optics and micro-electronic and micro-fluidic, new laser-based ultra-precise surface machining techniques are required. Therefore, the recently developed laser-induced plasma etching process (LIPE) was studied in relation to the remaining chemical as well as structural modifications after the etching of single crystalline silicon. For the studies, a fs-laser (775 nm, 150 fs, 1 kHz) with a pulse energy (EP) of maximum 750 µJ was focused to a CF4/O2 gas mixture at atmospheric pressure igniting a laser-induced plasma in front of the <100>Si sample. The reactive species of the laser-induced plasma (LIP) enable etchings up to a depth of 100 µm. For comparison, a silicon surface was also structured by direct laser ablation. The LIP etched surface that is characterized by SEM, TEM, XPS- and Raman-spectroscopy shows no melting features, no structural surface or subsurface defects and almost no chemical contamination from the etching process besides a silicon oxyfluoride layer with a thickness of approximately 2 nm on top of the atomically ordered silicon. The comparison shows clearly that the severe structural and chemical modifications at laser ablation of silicon can be avoided enabling ultraprecise surfaces machining.

16:15 Q&A    
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Laser-material synthesis : Maria Kandyla
Authors : 1/ Zeineb Raddaoui 2/ Marwa Bourguiba 3/ Pascal Marchet 4/ Jemai Dhahri 5/ Moez Chafra
Affiliations : 1/ - Laboratory of Condensed Matter and Nanosciences, Faculty of Sciences of Monastir, University of Monastir, Avenue of the environment , 5019 Monastir, Tunisia. - Institute for Research on Ceramics, University of Limoges, UMR 7315, 87068 Limoges, France. 2/ - Laboratory of Applied Mechanics and systems, School Polytechnic of Tunisia, University of Carthage, La Marsa, Tunisia. - Faculty of Sciences Tunis, University of Tunis el Manar, Tunis 2092. 3/ Institute for Research on Ceramics, University of Limoges, UMR 7315, 87068 Limoges, France. 4/ Laboratory of Condensed Matter and Nanosciences, Faculty of Sciences of Monastir, University of Monastir, Avenue of the environment , 5019 Monastir, Tunisia. 5/ Laboratory of Applied Mechanics and systems, School Polytechnic of Tunisia, University of Carthage, La Marsa, Tunisia.

Resume : In this work, we investigate the effect of rare earth ions substitution on the structural, optical, and conduction behaviors of Ba0.85Ca0.12RE0.03Ti0.90Zr0.04Nb0.042O3 (BCRETZN) (RE=Ce, Pr) compound ceramic produced via a solid-state route. The Rietveld analysis of the X-ray pattern at room temperature indicated a tetragonal structure (P4mm) of our compound ceramic. Afterward, the morphology of the ceramics was explored using scanning electronic microscope (SEM) as well as optical response and conduction behavior. The Photoluminescence properties revealed that the BCPrTZN sample gives rise to the green and red photoemissions under laser excitation at 450 nm at RT. Furthermore, for BCCeTZN sample, the photoluminescence spectra showed that strong violets emission bands were obtained, under excitation at 350 nm at RT The presence of Pr and Ce element in such materials may have significant technological promise in novel multifunctional devices.

Authors : Zharkova E. V. *(1), Averchenko A.V. (1), Salimon I.A (1), Abbas O.A. (1), Sazio P. J. A. (2), Lagoudakis P. G. (1), and Mailis S. (1).
Affiliations : (1) Skolkovo Institute of Science and Technology, Moscow, 121205, Russian Federation; (2) Optoelectronics Research Centre, University of Southampton, Southampton, SO17 1BJ, United Kingdom

Resume : Transition metal dichalcogenides (TMDs) are layered materials that have been lately the subject of an intense research effort due to their promise to become a versatile platform for photonics and electronics. Importantly alloying of these materials allows significant enhancement of their optoelectronic characteristics by broadening their spectral response range in photodetection devices. Currently, deposition of 2D materials onto various substrates is performed by transfer of the as-grown films from their substrates where they have been originally synthesized by different methods or isolated by mechanical exfoliation. With the exception of mechanical exfoliation, which is normally used for fundamental studies and prototyping, the methods that are commonly being used for the growth of TMDs involve high temperatures and a special atmosphere to prompt chemical reactions between the precursors, suppress oxidation and Sulphur loss. Recently, it has been reported that it is possible to synthesise MoS2 and WS2 by local laser-induced decomposition of (NH4)2MoS4 and (NH4)2WS4 respectively in ambient conditions. Local laser decomposition and synthesis of TMDs produces tracks of these materials with controllable thickness, which can be closely packed together to cover uniformly large areas. Due to the substrate-agnostic and local nature of this laser-synthesis process, there is no need to transfer the film from substrate to substrate as well as no additional steps for further micro-structuring of the films device fabrication. The reason for that is the ability to remove any unexposed precursor by simply immersing the laser-processed substrate into organic solvents that dissolve the unexposed precursor film preferentially, leaving only the synthesised TMD tracks on the surface of the sample. The simplicity of this method for the synthesis of TMDs implies the possibility of tuning the stoichiometry of the synthesised films by introducing additional components to form a composite source precursor solution. This approach has been used here to synthesise Mo(1-x)WxS2 alloys with variable stoichiometry, which depends upon the relative concentration of the (NH4)2MoS4 and (NH4)2WS4 precursors in the source solution. Tuning of the electrical and optical properties of the resulting film as a function of stoichiometry has been demonstrated. The conductivity of alloys with different compositions has been measured using transmission line measurements. Two-point contact devices with TMD alloy channels of variable lengths were fabricated for transmission line measurements. The results indicate an increase of the conductivity with increasing W content. Furthermore, field effect transistors and a double Schottky barrier photodetector were produced. A detailed analysis of the compositional content and a thorough electrical characterisation of the films will be presented. The authors acknowledge financial support from the Russian Science Foundation (RSF) (grant No. 21-79-20208)

Authors : B. Sotillo, R. Ariza, P. Fernández, J. Solis
Affiliations : B.S., R.A., P.F.: Department of Materials Physics, Faculty of Physics, University Complutense of Madrid, Madrid, 28040, Spain; R.A., J.S.: Laser Processing Group, Institute of Optics (IO-CSIC), Serrano 121, Madrid, 28006, Spain

Resume : The properties of different polymorphs of Nb2O5 have recently caught the attention of the scientific community for different emerging applications as energy storage devices, photocatalysis, sensors or resistive switching devices. However, Nb2O5 has some important drawbacks that hamper its practical applicability. First, pure Nb2O5 has a very low electrical conductivity (typically around 10-9 S·cm-1) that hinders the recollection of charge in energy storage devices or decreases the sensitivity in sensors. Second, it has a bandgap in the UV range, preventing its use as photocatalyst in the visible range. The generation of oxygen-deficiency in niobium pentoxide can increase both the electrical conductivity and the visible light absorption. In this work, we have studied the ultrafast-laser processing of Nb2O5 powders to form uniform and compact layers of oxygen-deficient sintered material. Moreover, the layers show an enhancement of several orders of magnitude of the electrical conductivity, which will be very useful for future applications.

Authors : F. C. Serra, G. Gaspar, A. S. Viana, I. Costa, D. M. Pêra, J. A. Silva, G. Hahn, L. Vines, J. M. Serra, K. Lobato
Affiliations : Instituto Dom Luiz (IDL), Faculdade de Ciências, Universidade de Lisboa, 1749-016, Lisboa, Portugal; Instituto Dom Luiz (IDL), Faculdade de Ciências, Universidade de Lisboa, 1749-016, Lisboa, Portugal; Centro de Química Estrutural, Faculdade de Ciências (CQE), Universidade de Lisboa, 1749-016, Lisboa, Portugal; Instituto Dom Luiz (IDL), Faculdade de Ciências, Universidade de Lisboa, 1749-016, Lisboa, Portugal;Instituto Dom Luiz (IDL), Faculdade de Ciências, Universidade de Lisboa, 1749-016, Lisboa, Portugal; Instituto Dom Luiz (IDL), Faculdade de Ciências, Universidade de Lisboa, 1749-016, Lisboa, Portugal; Department of Physics, University of Konstanz, 78464 Konstanz, Germany; Department of Physics, Center for Materials Science and Nanotechnology, University of Oslo, N-0371 Oslo, Norway; Instituto Dom Luiz (IDL), Faculdade de Ciências, Universidade de Lisboa, 1749-016, Lisboa, Portugal; Instituto Dom Luiz (IDL), Faculdade de Ciências, Universidade de Lisboa, 1749-016, Lisboa, Portugal

Resume : Hybrid silicon/perovskite tandem solar cells with a monolithic architecture (two terminals), require an interconnecting layer between the two sub-cells, which must: (i) efficiently transport each sub-cell carrier types, (ii) have a high vertical conductivity, but low lateral conductivity; and (iii) be optically transparent (low absorption and reflectivity) [1-3]. This interconnection layer can be fabricated as a recombination lawyer using transparent conducting oxides (TCOs) [4], or as a tunnel junction layer achieved either by amorphous silicon (a-Si) [5] or by a crystalline silicon tunnel junction (c-Si TJ) [6]. However, high-temperature perovskite top cell fabrication processes make a-Si and TCOs less appealing due to degradation of their electrical properties at higher temperatures, therefore, c-Si TJ are a promising and viable option. We present our approach to fabricate the interconnecting layer by creating a c-Si TJ on the silicon sub-cell using Gas Immersion Laser Doping (GILD) technique, to achieve an abrupt doping profile required for tunnel junctions. The GILD technique consists in doping a semiconductor by surrounding it with a dopant gas and then using ns laser pulses to melt the surface and hence allow the doping gas to diffuse into the melt before recrystallization [7]. Moreover, we think this approach is scalable, fast (0.5 to 10 cm2/min of laser processed area), cost-effective and compatible with existing silicon cell production lines. The experimental setup consists of two main systems, the reaction chamber and the laser apparatus. The cylindrical reaction chamber is made in aluminium with an IR-transparent window and can hold up to 10×10 cm2 silicon wafers. Connected to the chamber is a gas feed system, capable of delivering both argon and POCl3 through a bubbler containing the liquid phosphorus precursor. A 1064 nm solid-state pumped laser with a 0.04 mJ pulse energy, a 500 kHz pulse rate and a 20 μm beam diameter is coupled to a high speed galvano head, allowing for successive laser rastering sequences that melt the Si wafer surface. Laser rastering parameters, such as distance between consecutive laser spots (d = 1.0, 1.5, 2.0, 2.5 and 3.0 µm) and number of rastering sequences (n = 1, 3, 6, 9 times) were varied and combined to obtain a wide range of 5×10 mm2 laser processed areas with different doping depth profiles [8, 9]. p+ (100)-oriented Cz-Si wafers with a p++ emitter were phosphorus doped. Secondary ion mass spectrometry (SIMS) depth profiling was used to characterize the sample elemental composition. The activity of the dopants is also characterized by the electrochemical capacitance-voltage (ECV). Results show successful surface doping with a flat phosphorus concentration within the 10^19-10^20 cm-3 range, followed by an abrupt “shoulder”. Boron from the emitter accumulates at the maximum melt depth, around 200 to 300 nm, clear evidence of the well-known pile-up phenomenon [10]. Laser rastering parameters, like distance between consecutive laser spots and number of rastering sequences, have a great influence on the shape of the phosphorus doping profile, but also change the underling boron emitter profile due to pile-up. By tuning the laser rastering parameters, the phosphorus and boron depth profiles can be adjusted to further attain the desirable TJ properties. References [1] Y. Ko et al., “Recent Progress in Interconnection Layer for Hybrid Photovoltaic Tandems”, Adv. Mater. 32, 2002196 (2020). [2] M. Jošt et al., “Monolithic Perovskite Tandem Solar Cells: A Review of the Present Status and Advanced Characterization Methods Toward 30% Efficiency”, Adv. Energy Mater. 10, 1904102 (2020). [3] S. Akhil et al., “Review on perovskite silicon tandem solar cells: Status and prospects 2T, 3T and 4T for real world conditions”, Mater. Des. 211 (2021) 110138. [4] S. Albrecht et al., “Monolithic perovskite/silicon-heterojunction tandem solar cells processed at low temperature”, Energy Environ. Sci. 9 (2016) 81. [5] P. Schulze et al., “25.1% High-Efficiency Monolithic Perovskite Silicon Tandem Solar Cell with a High Bandgap Perovskite Absorber”, Sol. RRL 4 (2020) 2000152. [6] F. Sahli et al., “Fully textured monolithic perovskite/silicon tandem solar cells with 25.2% power conversion efficiency”, Nature Mater. 17 (2018) 820. [7] G. B. Turner et al., “Solar cells made by laser‐induced diffusion directly from phosphine gas”, Appl. Phys. Lett. 39 (1981) 967. [8] G. Gaspar et al., “Sequential silicon surface melting and atmospheric pressure phosphorus doping for crystalline tunnel junction formation in silicon/perovskite tandem solar cells”, Proceedings of the 37th European PV Solar Energy Conference and Exhibition (EU PVSEC), Lisbon, 2020, pp. 765-768. [9] G. Gaspar et al., “Tunnel Junction Formation on Silicon P++ Emitters by Gas Immersion Laser Doping”, Proceedings of the 38th European PV Solar Energy Conference and Exhibition (EU PVSEC), Lisbon, 2021, pp. 521-524. [10] P. Lill, et al., “Boron Partitioning Coefficient above Unity in Laser Crystallized Silicon”, Materials 10 (2017) 189.

Authors : C. Ozçelik1, H. Amaveda1, M. Mora1, E. Martínez1, B. Ozçelik2, G.F. de la Fuente1, L. A. Angurel1
Affiliations : 1Instituto de Nanociencia y Materiales de Aragón (CSIC-University of Zaragoza), Zaragoza, Spain 2 Department of Physics, Faculty of Sciences and Letters, Çukurova University, Adana, Turkey

Resume : Laser Additive Manufacturing is frequently used for the fabrication of complex materials. Its application to ceramic elements is finding difficulties associated to their characteristic properties. The high temperature gradients reached during the laser treatment generate thermomechanical stresses that lead to the formation of cracks. These can be strongly reduced if the laser treatment is performed at relatively high substrate temperatures, inside a patented Laser Furnace (LF) apparatus. This enables an alternative way to process ceramic and glass surfaces under extreme conditions. In addition, laser irradiation is performed using the Laser Line Scan method, in order to achieve large scale, continuous processes offering the potential for tuning the coating thickness for the applications desired. This method has been applied to process ceramic materials with different properties, demonstrating attractive mechanical and optical properties in 600 x 600 mm clay tiles with decorative patterns. The present work deals with dense dielectric Al2O3 and Al2O3-ZrO2 eutectics, as well as with Bi2Sr2CaCu2O8+ superconductors, with dimensions approaching 60 mm x 60 mm. Laser treatments were performed using CO2 (mid-IR) and fiber (n-IR) lasers. In some cases, sample volume temperatures at which the laser treatment was performed have approached values of 1200 °C, thereby reducing or avoiding the generation of cracks within the ceramic material. Additional ceramic layers were applied by deep coating prior to additional laser furnace cycles, so that the desired coating thickness was achieved. Processing and coating parameters were optimized to assure the adequate integration of the different built-up layers, while maintaining the stability of the resolidified ceramic. In addition, the distribution of the laser energy on the sample surface was adjusted to obtain a stable solidification front along the full sample width and produce an ordered microstructure in both cases, the eutectic and the superconductor ceramics. The results obtained with this new technology will be discussed in connection with the expected properties and applications of both types of products, dielectric and superconducting ceramics, as highlights of the advantages provided by the unique combination of Lasers with continuous furnaces. This paves the way to continuous ceramic manufacturing processes leading to dense microstructures free of microcracks. Acknowledgements: Work funded by the Spanish MCIN/AEI/10.13039/501100011033 (project PID2020-113034RB-I00) and by Gobierno de Aragón (research group T54_20R). B. O. acknowledges to the Scientific and Technological Research Council of Turkey (TUBITAK) for a grant via 2219-Science Fellowships and Grant Programmes Department, with the project number:1059B192000390. Authors also would like to acknowledge the use of Servicio General de Apoyo a la Investigación-SAI, Universidad de Zaragoza.

Authors : Danijela Ignjatovic Stupar, Grégoire Robert Chabrol, Thierry Cutard, Sylvain Lecler, Jocelyne Brendle
Affiliations : International Space University; ECAM Strasbourg-Europe; IMT Mines Albi-Carmaux; INSA of Strasbourg; IS2M

Resume : Additive manufacturing using regolith, the main in-situ material resource, is offering a solution for long duration stay on the Moon or Mars. Buildings and tools can be manufactured on demand and save transportation cost and time. To prepare the future exploration and optimize the process beforehand, a Selective Laser Melting (SLM) machine, using a power bed, has been developed by our research team. The experimental process was monitored by a pyrometer. Various lunar soil simulants have been used in this system. This study compares the melted samples made off the various simulants and characterized by XRD. The sample porosity and microhardness were measured to choose the best processing parameters. Furthermore, the process conditions were optimized by a numerical model developed on COMSOL Multiphysics. This model is based on data from the literature to cover material properties such as latent heat of fusion and temperature dependent parameters like the thermal conductivity, the thermal capacity, and the density. The meshing was adapted to the optimize the model efficiency. The laser source was modelled as a gaussian beam. The simulation was done with both a static and a moving beam where the effect of power, beam size and scanning speed was investigated. The evolution of temperature of the melt pool, the deformation of the structures and the evolution of the built-in stress were evaluated. This study shows that the outcome from the numerical model corroborates the experimental results in terms of spot size and temperature of the melt pool. The model predicts the failure of the sample for threshold values of power and scan speed for a given spot size.

10:45 Q&A    
11:00 Coffee Break    
Laser processing and applications : Patricia Alloncle
Authors : Thomas Doualle, Matthieu Reymond, Vincent Klosek, Jerome Sercombe, Laurent Gallais and Yves Pontillon
Affiliations : CEA, DES, IRESNE, DEC, Cadarache F-13108 Saint-Paul-Lez-Durance, France; Aix Marseille Université, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France

Resume : In the field of nuclear fission research, laser-heating constitutes a very powerful technique for submitting various materials (metal, alloy, oxide, etc.) to thermal stresses at a laboratory scale and analysing their response in situ. For several years, CEA in collaboration with CNRS has developed multi-objective laser heating platforms (CHAUCOLASE – Chauffage Contrôlé par Laser - in CNRS/Institut Fresnel and CHARTREUSE in CEA Cadarache) based on high power lasers to address various research topics: study of nuclear fuels at very high temperature, characterization of the thermo-physical properties and samples preparation. These experimental devices rely on high-power Ytterbium fibre lasers, dedicated experimental chambers, specific sample holders, optical systems to generate laser beams of variable shapes and intensities, and lastly the associated instrumentation (pyrometers, high-speed and high-resolution infrared cameras, in-situ microscopes, temperature control systems, etc.). These experimental developments are coupled with theoretical approaches regarding laser/material interactions. These two platforms have been designed to be modular in order to access to many experimental configurations and study different topics that we present in this contribution: 1. Thermal transients. These studies are in line with a general continuous improvement of nuclear power reactors safety. The challenges relate to quantifying the impact of specific thermal transients at extremely high temperatures on the materials used in fuel elements to understand/quantify the mechanisms involved in their behaviours and validate the corresponding fuel performance codes developed at CEA with separate effect approaches. Various types of thermal transients can be reproduced in our facilities: temporal dynamics (from ms to h) and spatial distributions (from few µm to cm) representative of hypothetical accident conditions encountered in reactors. One of the most challenging is the Reactivity-Initiated Accident, which is characterized by a very fast rise and strongly localized temperature. During these experiments, we perform temperature elevations, with the associated diagnostics, of more than 2500K, at the periphery of a UO2 sample, in a few tens of millisecond and we correlate the temperature gradients to the mechanical behaviour of the samples. 2. Thermal properties. The knowledge of material properties at high temperature is critical in the context of the evaluation and understanding of irradiated fuel performances. We have therefore developed two techniques that involve laser material-interactions to evaluate thermal properties of nuclear fuel and their evolution as a function of temperature (up to 3000K). We have implemented both techniques on both facilities. Experiments on graphite, as material model, as well as on UO2, are conducted. We present in this paper results for both techniques which allow thermal conductivity quantification thanks to diffusivity measurements: • The laser-flash method, based on a laser-flash excitation and an infrared thermography, is a non-contact measurement of the thermal response of a studied sample. • The Infrared microscopy technique, which presents a spatial resolution of few tens of microns. It is based on the detection of the surface sample temperature rise distribution induced by the absorption of an intensity-modulated focused laser beam. 3. Laser micro/macro-machining of nuclear fuels. A better-detailed description of the behaviour of the nuclear ceramic during thermal transient requires access to local information within the fuel pellet, from the order of a few hundred of microns to millimetres. Except laser micromachining, few techniques are capable of handling such a range and even fewer are applicable to nuclear fuels. We will present experimental, numerical studies carried out in our platforms, and we will show that such laser cutting technique can produce slices with excellent quality (reduced affected area, no recast layer, no micro-cracks and no debris from ejected material) with high efficiency (cutting depth of 1.5 mm, 60 µm kerf width and 2° taper angle). First experiments show the possibility to apply laser ablation technique to nuclear fuels. This work is also supported by EDF and Framatome in the frame of the Tripartite Institute (CEA/EDF/FRA).

Authors : Egorov E.V.(1,2,3), Egorov V.K.(1)
Affiliations : (1) Institute of Microelectronics Technology Russian Academy of Science (IMT RAS) (2) Institute of Radio Engineering and Electronics Russian Academy of Science (IRE RAS) (3) Financial University under the Government of the Russian Federation

Resume : Laser radiation fluxes accordingly to conventional paradigm propagate in optical waveguides-fibers in frame of the multiple consecutive internal total reflection on the so-called zigzag scheme. It is expected that the laser radiation fluxes propagation takes place in case of the consecutive reflections phasing. But the conventional approach ignores three principle factors connected with appearing of the local interference field of standing radiation wave owing to interference between incident and reflected fluxes, existence of the radiation quasimonochromatism defined by radiation wavelength and it dispersion and the spatial coherence. The total internal reflection phenomenon is accompanied by the laser radiation standing wave interference field appearing with longitudinal and transversal sizes are equal to half of the laser radiation coherence length. Taking into account three pointed factors we showed that the laser radiation fluxes can be transported by optical waveguides on base of the multiple internal total reflection mechanism or in result of the waveguide-resonance fluxes propagation in according with relation between the optical core dimension and half of the radiation coherence length. When the optical core magnitude is higher as the radiation coherence length half laser fluxes will be transported accordingly to the multiple total reflection mechanism. In otherwise case, the waveguide-resonance mechanism of the laser fluxes propagation will be realized. It is known that the light core size in optical fibers is usually smaller as 1 mm, whereas the coherence length of the laser radiation can obtain some hundred meters. This relation allows to affirm that the laser radiation fluxes are transported by optical fiber in frame of the waveguide-resonance propagation mechanism and the conventional paradigm is erroneous and must be revised. The report presents main characteristics of the radiation fluxes waveguide-resonance propagation mechanism and points on its universality.

Authors : G. Chatzigiannakis, A. Jaros, R. Leturcq, J. Jungclaus, T. Voss, S. Gardelis, M. Kandyla
Affiliations : Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos Constantinou Avenue, 11635 Athens, Greece; Institute of Semiconductor Technology, Braunschweig University of Technology, Hans-Sommer Strasse 66, 38106 Braunschweig, Germany; Materials Research and Technology Department, Luxembourg Institute of Science and Technology, 41 Rue du Brill, L-4422 Belvaux, Luxembourg; Institute of Semiconductor Technology, Braunschweig University of Technology, Hans-Sommer Strasse 66, 38106 Braunschweig, Germany; Institute of Semiconductor Technology, Braunschweig University of Technology, Hans-Sommer Strasse 66, 38106 Braunschweig, Germany; Department of Physics, National and Kapodistrian University of Athens, Panepistimiopolis Zografos, 15784 Athens, Greece; Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos Constantinou Avenue, 11635 Athens, Greece

Resume : Zinc oxide (ZnO) is a very promising material for optoelectronic applications due to its direct wide bandgap (3.37 eV) and large exciton binding energy at room temperature (60 meV). However, the development of blue-UV optoelectronic devices based on ZnO homojunctions is hindered by the difficulty in introducing reproducibly high-quality p-type impurities in ZnO, which exhibits intrinsically n-type conductivity. Therefore, ZnO is usually combined with p-doped semiconductors, most commonly with silicon, which is a narrow-bandgap material and extends the operation of ZnO optoelectronic devices to the visible-near infrared (vis-NIR) spectral range. A wide variety of ZnO/p-Si photodetectors have been developed with high response in the UV-visible spectral range. In some cases, selective detection of UV or visible light has been achieved, which is useful for filterless optoelectronic applications, such as imaging, spectroscopy, and machine vision. In addition to n-ZnO/p-Si heterojunctions, which operate as p-n junction minority-carrier devices, n-ZnO/n-Si isotype heterojunctions form an interesting class of majority-carrier devices. In such devices, a weak built-in potential barrier is formed between the two materials, which enables a two-way current flow. The two-way current flow of the isotype junction is useful for wavelength-selective photodetection, as the net current changes polarity and intensity depending on the illumination wavelength. This is in contrast to the more common p-n junctions, where a strong built-in potential barrier is established between the p- and n-type materials, and which operate based on an entirely different mechanism. In this work, an isotype heterojunction n+-ZnO/n-Si photodetector is developed, demonstrating wavelength-selective or broadband operation, depending on the applied bias voltage. Specifically, it demonstrates a high NIR responsivity at positive bias voltage and a broadband responsivity at negative bias voltage. This feature is complementary to the existing n-ZnO/p-Si selective photodetectors, which detect either UV or visible radiation but do not distinguish between NIR and UV/visible radiation. Additionally, even at self-powered (zero bias) operation, it distinguishes between UV, visible, and near IR (NIR) photons by polarity control of the photocurrent. The photodetector is developed by atomic layer deposition (ALD) of ZnO on n-Si, followed by electric contact deposition and annealing. Photoluminescence measurements reveal high optical quality and improved crystallinity of annealed ZnO on silicon. Photocurrent measurements as a function of illumination wavelength and bias voltage show small negative values in the UV-visible spectral range at zero and positive bias voltage and high positive values in the NIR spectral range. At negative bias voltage, the device shows broadband operation with high photocurrent values across the UV-vis-NIR.

Authors : M. Kanidi, A. Papadimitropoulou, C. Charalampous, Z. Chakim, G. Tsekenis, A. Sinani, C. Riziotis, M. Kandyla
Affiliations : Νational Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vasileos Constantinou Ave., Athens 11635, Greece; Biomedical Research Foundation of the Academy of Athens, 4 Soranou Ephessiou St., 115 27 Athens, Greece; Biomedical Research Foundation of the Academy of Athens, 4 Soranou Ephessiou St., 115 27 Athens, Greece; Biomedical Research Foundation of the Academy of Athens, 4 Soranou Ephessiou St., 115 27 Athens, Greece; Biomedical Research Foundation of the Academy of Athens, 4 Soranou Ephessiou St., 115 27 Athens, Greece; Νational Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vasileos Constantinou Ave., Athens 11635, Greece; Νational Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vasileos Constantinou Ave., Athens 11635, Greece; Νational Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vasileos Constantinou Ave., Athens 11635, Greece;

Resume : Breast cancer is the most common type of cancer observed in women. Communication with the tumor microenvironment allows invading breast cancer cells, such as triple negative breast cancer cells, to adapt to specific substrates. To elucidate the mechanisms underlying cancer cell survival, proliferation, and metastatic potential in vitro, a number of parameters should be taken into consideration such as the surface chemistry, surface stiffness, and topographic characteristics. Indeed, the substrate topography modulates the cellular behavior, as it has been shown that topographical features of different length-scales, ranging from nano- to micrometer ones, have a strong influence on cell adhesion, morphology, alignment, and contact guidance. The ideal substrate for tumor cell culturing should be able to combine effectively mechanical properties and macro/nano scale topography in order to achieve the optimal conditions for cell survival and, most importantly, to mimic the microenvironment cells naturally reside in. A number of different materials and micro/nanofabrication techniques have been employed to develop substrates for cell culturing. Silicon-based substrates present many advantages as they are amenable to a wide range of processing techniques and they permit rigorous control over the surface structure. In this work, we investigate and compare the response of MDA-MB-231 cells on laser-patterned silicon substrates with two different topographical scales, i.e., the micro- and the nanoscale, in the absence of any other biochemical modification. We were able to develop silicon surfaces with distinct morphological characteristics by employing two laser systems with different pulse durations (nanosecond and femtosecond) and different processing environments (vacuum, SF6 gas, and water). Laser processing of silicon has been shown to generate a variety of structures at the micro- and nanoscale by tuning the fabrication parameters, such as wavelength, pulse duration, fluence, gas or liquid environment, and the number of incident laser pulses. Laser-patterned silicon substrates have been used for the culture of Schwann cells, fibroblasts, and rat pheochromocytoma (PC12) cells, but have not been applied to TNBC (MDA-MB-231) cell culturing before. Our findings demonstrate that surfaces with micro-topography are repellent, while surfaces with nano-topography are attractive for MDA-MB-231 cell adherence. Furthermore, laser patterning of surfaces allows for localized surface modification and high spatial resolution of the formed structures, thus paving the way for the design of co-culturing substrates and devices based on topographical cues. In this way, invaluable information on the proliferative and migrating behavior of breast cancer cells will be provided, which will enable the formulation of novel treatment approaches.

12:45 Q&A    
13:00 Concluding remarks    
13:45 Plenary III    

No abstract for this day

Symposium organizers
Alexandra PALLA-PAPAVLUNational Institute for Lasers, Plasma, and Radiation Physics

Atomistilor 409 077125, Magurele Romania

+40 (021) 457 44 14
Anne-Patricia ALLONCLECentre National de la Recherche Scientifique LP3 - CNRS

163 Av de Luminy, C917, 132288 Marseille Cedex 9, France

+33 620867783
Evgeny GUREVICHUniversity of Applied Science Munster

Stegerwaldstr. 39, 48565, Steinfurt, Germany

+49 2551 962322
Maria KANDYLANational Hellenic Research Foundation

48 Vas. Constantinou Ave., 11635 Athens, Greece

+30 2107273826