Symposium : R
Laser processing and diagnostics for micro and nano applications
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| 08:50 | Welcome to Symposium R - Chairs: I. Zergioti, R. Eason, M. Nistor, J. Perriere, J. Solis | |
| Templating and surface processing : Craig Arnold | ||
| 09:00 | Holographic Patterning of Optoelectronically Active 3D Photonic Crystals Authors : Paul V. Braun, Sidhartha Gupta, Erik C. Nelson, Masao Miyake, Agustin Mihi Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 USA Resume : We show that optoelectronically active materials including ZnO, GaAs, and rare-earth doped glasses can be structured into 3D photonic crystals using polymer and inorganic templates formed by holographic patterning. For several of these systems, we have also achieved direct electrical pumping, which is enabled by the very high quality of the templated material. For example, the templated GaAs photonic crystal is single crystalline, having been grown via MOCVD using conditions where GaAs nucleation on the template is very low and GaAs growth on the GaAs substrate remains high. After removal of the template, the result is a single crystal of GaAs containing a 3D periodic array of pores. Active quantum wells can be embedded within the GaAs structure and electrically pumped. Materials such as ZnO and rare-earth doped glasses can be embedded as defects within a photonic crystal as well, through a unique photoresist stacking approach we developed. The optical and electronic properties of these structures will also be discussed. | R1 1 |
| 09:30 | Modeling of CW laser diode irradiation of amorphous silicon films Authors : Z. Said-Bacar, Y. Leroy, F. Antoni, A. Slaoui, E. Fogarassy InESS (UMR 7163 CNRS-Univ. Strasbourg) , BP 20 CR, 23 rue de Loess, 67037 Strasbourg Cedex 2, France Resume : Thin Film polycrystalline silicon with large grains (>100µm) is an alternative material to form high efficiency solar cells as it offers reduced grains boundaries density and therefore higher electronic quality compared to fine grained silicon based cells. Laser processing of amorphous silicon is reported as an appropriate method to reach large grains polysilicon films. Recently, laser crystallization using a CW laser diode (λ=806 nm) allowed to obtain large grain size for optimized laser parameters conditions. It has been shown that to reach very large grains the laser power must be close to the ablation threshold [1]. In this case, the maximum energy is stored in the material which will decrease the cooling rate allowing growing grains of large size. However, few work reports on the modelling of such process.
The aim of this work is to determine the optimal parameters required to crystallize thin amorphous silicon films on glass substrate with a continuous wave (cw) laser diode (λ=806 nm), using a numerical model developed in COMSOL Multiphysics. Structures with different amorphous silicon, with dielectric barrier or capping layer were considered. The numerical simulation of the laser crystallization process takes into account the solid-liquid phase change and the difference between the melting temperature of amorphous (Tma-Si=1420 K) and crystalline silicon (Tmc-Si=1690 K) silicon, respectively. We have varied the main parameters controlling the crystallization process, namely the power and the scan speed of the laser. Furthermore the initial temperature and the thickness of the a-Si layer were also varied in order to optimize the process. We have determined the energy melting threshold versus the different parameters and for different structures. We have also identified that the cooling rate can be a crucial parameter that can governs the grain size. Comparisons between numerical and experimental data will also be presented.
[1]: « CW argon laser crystallization of silicon films: Structural properties », J. F. Michaud, R. Rogel, T. Mohammed-Brahim, M. Sarret, Journal of non-crystalline solids, 352, (2006), 998-1002 | R1 2 |
| 09:45 | Pulsed laser annealing of pure and Ag-containing AlN films grown by pulsed laser deposition and sputtering Authors : H. Zoubos1, D.C. Koutsogeorgis2, W.M. Cranton2, P. Patsalas1 1Department of Materials Science and Engineering, University of Ioannina, Ioannina, 45110, Greece 2School of Science and Technology, Nottingham Trent University, Nottingham, NG11 8NS, United Kingdom Resume : Aluminum Nitride (AlN) is one of the most widely used materials in photonics and has been grown using a variety of deposition techniques such as Pulsed Laser Deposition (PLD) and Magnetron Sputtering (MS). The microstructure of the AlN films are strongly affected by the deposition technique and conditions and for certain applications a post growth thermal processing is necessary to achieved the desired optical and optoelectronic properties. An alternative pathway for the post growth processing of AlN is laser annealing, which might be applied with very high spatial resolution and to films grown onto temperature-sensitive substrates. In this work we have grown a variety of AlN films on Si and sapphire by PLD and MS, which exhibit different microstructure (amorphous for PLD, polycrystalline with wurtzite structure for MS), density, refractive index (1.9 for PLD and 2.2 for MS) and fundamental gap (~4.5 eVs for PLD, >5.5 eVs for MS), as well as sputtered Ag-containing AlN films, where the Ag is atomically dispersed into AlN (AlN:Ag). We employ pulsed KrF and ArF laser annealing to these films and we identify the structural changes, which occur, and their effect on the films’ optical properties (using optical reflectance spectroscopy). We study the sub-bandgap laser annealing and the effect of the substrate, comparing the annealing results to films grown on Si and sapphire. Finally, we study the effect of laser annealing on the AlN:Ag films and we investigate the possible ordering of Ag into AlN. | R1 3 |
| 10:00 | Microstructures and mechanical properties of metallic NiCrBSi and composite NiCrBSi-WC layers manufactured via hybrid plasma/laser process Authors : Nicolas SERRES 1, Françoise HLAWKA 1, Sophie COSTIL 2, Cécile LANGLADE 2, Frédérique MACHI 3 1 LISS, INSA de Strasbourg, 24 Boulevard de la Victoire, 67000 Strasbourg, France 2 LERMPS – UTBM, site de Sévenans, 90010 Belfort cedex, France 3 IREPA LASER - Pôle API - Parc d\'Innovation - 67400 Illkirch, France Resume : Thermal spraying is already used in industry to protect mechanical parts against wear and/or corrosion, but results are not always satisfactory for reasons of porosity and microstructures. In this study, atmospheric plasma spraying (APS) and in situ laser irradiation by diode laser processes were combined to modify structural characteristics of metallic NiCrBSi and composite NiCrBSi-WC coatings. The microstructure evolution was studied with the chemical composition analysis by XRD and SEM coupled with EDS techniques; microhardness characterization and residual stresses. Instrumented nanoindentation tests were also conducted employing a Berkovich indenter. Moreover, the effect of the influence of the volume fraction of the reinforced WC particles on the formation and mechanical performances of the layer was also investigated.
Results show that in situ laser remelting induces the growth of a dendritic structure which strongly decreases the porosity of as-sprayed coatings and improves the mechanical properties of the layer. Furthermore, the layer properties such as its porosity, microhardness and elastic modulus are determined by the percentage of WC particles in the mixture. Several technical parameters were investigated, especially the laser energy density, in order to establish a better configuration to obtain coatings without solidification cracking, one of the major defects that can occur during solidification of metallic or composite alloys. | R1 4 |
| 10:15 | Tribological study of Nd: YAG laser treated titanium plates: A novel approach by multianalysis (Raman, XPS, NRA and PIXE) Authors : L. Lavisse (a), P. Berger (b1,b2), G. Pillon (a), M.C. Marco de Lucas (a) (a) Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 5209 CNRS-Université de Bourgogne, 9, Av. Alain Savary, BP 47870 - F-21078 Dijon Cedex. France. (b1) CEA, DSM/IRAMIS/SIS2M , CEA-SACLAY F-91191 Gif s/ Yvette Cedex France (b2) CNRS, UMR SIS2M (CEA-CNRS) - CEA/SACLAY, 91191 Gif sur Yvette Cedex, France. Resume : Titanium and its alloys exhibit poor tribological properties in friction and wear as well. Review papers have stated that nitridization (TiNx) and/or oxidation (TiOx) improves titanium friction behavior. The present study deals with laser-assisted insertion of light elements present in air such nitrogen, oxygen and carbon using two laser sources (Nd:YAG) with two different pulse durations (5ns or 35 ns), and with tribological behavior of exposed surfaces. We have studied modifications of dry friction properties of titanium oxi-nitride layers, related to laser pulse duration. From the early cycles, tribological behavior is sensitive to the nature of surface oxides or nitrides. However, their role and contribution to the overall tribological response are not mastered nor understood yet. For this purpose, we have characterized laser treated surfaces, pristine and final layers, both for morphology (SEM, surface profiling), structure (Raman spectroscopy) and elemental composition (Nuclear Reaction Analysis and Particle Induced X-ray Emission). We propose a tentative mechanism of the role of titanium oxides and nitrides in the detachment of contact particles. | R1 5 |
| 10:30 | BREAK | |
| Pulsed Laser Deposition 1 : Henley Simon | ||
| 11:00 | Effects of plume confinement on the growth of catalytic nanoparticles by pulsed laser ablation of C:Ni targets Authors : Authors: James Fryar, K. D. G. Imalka Jayawardena, Y. Y. Tan, A. A. Damitha T. Adikaari, Simon J. Henley, S. Ravi P. Silva Affliations (all): Nano-Electronics Centre, Advanced Technology Institute, University of Surrey, GU2 7XH, England Resume : Pulsed laser ablation of a carbon-nickel composite target (80:20% by wt.) was used to produce nanostructured carbon thin films embedded with Ni nanoparticles. In this report we investigate the effect of background gas pressure on the laser-produced plumes, and relate changes in the dynamics and composition of the plumes to the resultant size and distribution of Ni particles within the deposited films.
Plume composition, confinement, and cluster formation were studied using wavelength-filtered iCCD imaging, temporally/spatially resolved optical emission spectroscopy, and Rayleigh scattering experiments. The resultant thin film structure was examined using Raman spectroscopy and SEM. Ni-embedded films showing high graphitisation were subsequently used to catalyse the growth of carbon nanotubes by plasma enhanced chemical vapour deposition.
We demonstrate that the formation of nanoclustered C:Ni material occurs at elevated background pressures and is a consequence of the plume confinement. The link between plume confinement and the final PECVD nanotube morphology is also discussed. | R2 1 |
| 11:15 | Laser processing of C60 fullerene thin films Authors : S. Canulescu1, J. Schou1 1Department of Photonics Engineering, Risø Campus, DTU, DK-4000 Roskilde, Denmark Resume : Thin films of C60 were deposited by matrix assisted pulsed laser evaporation (MAPLE), where the target is a frozen solution of fullerene (C60) in water. MAPLE provides a gentle transfer of small and large molecular weight species from the solid phase into vacuum. It relies on soft desorption of the molecules into the gas phase with little or no photochemical damage. This approach allows the processability of the C60 molecules into thin films of C60, and for other fullerenes it can be of a large interest for solar cells applications. The surface morphology of the C60 thin films deposited on 7 mm × 7 mm Si wafers was analyzed by scanning electron microscopy and atomic force microscopy. Analyses by MALDI mass spectroscopy have shown that a significant fraction of the C60 fullerene cages remain intact when the deposition conditions are optimized.
The morphological and structural properties of the films were compared to those obtained by classical PLD, where a pressed target of C60 powder was irradiated in vacuum. The results show that the PLD- synthesized films also contain photodecomposed components, resulting in variation of their physical properties. | R2 2 |
| 11:30 | PULSE LASER DEPOSITION OF La0.6Ca0.4MnO3. ION DYNAMICS AND THIN FILM PROPERTIES Authors : M. Esposito1, T. Lippert1, C.W. Schneider1, A. Wokaun1 1Paul Scherrer Institut, General Energy Research Department, 5232 Villigen, Switzerland Resume : The growth of manganite thin films by pulsed laser ablation (PLD) is challenging due to the manganite’s composition dependent rich phase diagram. To grow manganite thin films with the desired properties, it is therefore important to understand the chemical processes in the plasma plume during the ablation. In this study Langmuir probe, emission spectroscopy, quartz micro balance and quadrupole mass spectrometry were employed to fully characterize the plasma species and their energy distribution in the plume. The manganite thin films were prepared using a ArF excimer laser (=193 nm) from a La0.6Ca0.4MnO3 target in vacuum and N2O and O2 background gases. After the film deposition the respective composition was analyzed in-situ by secondary ion mass spectrometry (SIMS).
For a vacuum ablation, the plume consists largely of metal atoms and ions (La, Ca, Mn, O, LaO) as well as multiatomic species like LaMnO+. The LaO+ diatomic species are by far the most intense diatomic species in the plume, while CaO and MnO are only detected in small quantities. The interaction of a reactive N2O gas pulse with the ablation plume leads to a significant increase in plume reactivity even compared to an O2 atmosphere. This enhanced reactivity is desired to grow manganite thin films in order to achieve the desired oxygen content. A comprehensive comparison between the optimized plasma conditions, film composition and structural as well as transport data will be presented. | R2 3 |
| 11:45 | Development of laser deposited Multilayer Zone Plates for soft X-ray Radiation Authors : Tobias Liese1, Michael Reese2, Peter Großmann2, Klaus Mann2, and Hans-Ulrich Krebs1 1) Institut für Materialphysik, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany 2) Laser-Laboratorium Göttingen e.V., Hans-Adolf-Krebs-Weg 1, 37077 Göttingen, Germany Resume : Microscopy using water window soft x-rays with wavelengths of between 2.3-4.4 nm is a highly useful technique for biological sciences, polymers research, colloidal science and even earth science. A novel approach for the application of focusing soft X-rays in the water window regime is to prepare non-periodic multilayer structures, which can be designed for use as one- or two-dimensional zone plates in Laue diffraction geometry. For this purpose, high quality non-periodic ZrO2/Ti multilayer zone plates were deposited by pulsed laser deposition (PLD) at 248 nm. The interfaces within the multilayers have to be positioned according to the Fresnel zone plate law. The ZrO2/Ti multilayer system was chosen due to the high contrast, low interface roughness, high thermal stability, and due to the efficient smoothing tendency of ZrO2 [1, 2]. The zone plates were fabricated by cutting slices out of the multilayers by focused ion beam (FIB) and fixing them directly over pinholes within SiN substrates. Using a table-top X-ray facility [3], the focusing abilities of the structures were determined at a wavelength of 2.87 nm. In this contribution, results of the Laue Zone plate fabrication by PLD and FIB, and the lens characteristics are presented.
[1] C. Fuhse, H.U. Krebs, S. Vitta, and G.A. Johansson, Appl. Opt. 43 (2004) 6265.
[2] J. Röder, H.U. Krebs, Appl. Phys. A 90 (2008) 609.
[3] C. Peth, F. Barkusky, and K. Mann, J. Phys. D: Appl. Phys. 41 (2008) 105202. | R2 4 |
| 12:00 | ULTRAFAST LASER ABLATION AND DEPOSITION OF WIDE BAND GAP SEMICONDUCTORS Authors : M. Sanz, M. López-Arias, R. de Nalda, M. Castillejo* Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain) S. Amoruso, G. Ausanio, R. Bruzzese, S. Lettieri, X. Wang Coherentia CNR-INFM and Dipartimento di Scienze Fisiche, Università degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy) Resume : We report on the properties of the ablation plume and the characteristics of the films produced by ultrafast PLD (about 300 fs, at 527 and 263 nm) of CdS and ZnS semiconductors. We analyzed the modification of the targets induced by different number of laser shots, deriving the damage/modification threshold and incubation coefficient of the materials. Plume characteristics were studied by exploiting time and space resolved emission spectroscopy and gated imaging. By appropriately changing the number of laser shots, we obtained less than one layer deposits consisting of isolated nanoparticles on mica substrates, and nanoparticle-assembled films on Si substrates. Crystalline quality and composition of the deposits was studied by using X-ray diffraction and X-ray photoelectron spectroscopy, while the surface morphology was analyzed by environmental scanning electron microscopy and atomic force microscopy. Photoluminiscence of the deposited films was also measured at room temperature.
The results are discussed in terms of the composition and expansion dynamics of the semiconductor plasma plume and of the properties of the deposited nanoparticles and nanostructured films. These results also allow investigating the influence of the laser irradiation wavelength on the obtained nanostructures in a range of laser fluences that are suitable for obtaining deposits. | R2 5 |
| 12:15 | YSZ thin films deposited by PLD and magnetron sputtering for SOFC technology Authors : H. HIDALGO(1), E. REGUZINA(1), J. MATHIAS(1), E. MILLON(1), A-L. THOMANN(1), C. LEBORGNE (1), P. BRAULT(1), D. DAMIANI(2), T. SAUVAGE(3), A. PINEAU(4) (1) GREMI, UMR CNRS 6606 Universite d Orleans 14, rue d Issoudun F-45067 Orleans (2) CEA-Le Ripault, F-37260 Monts (3) CEMHTI, UPR CNRS 3079, 3A rue de la Ferrolerie, F-45071 Orleans (4) CRMD, UMR CNRS 66190 Universite d Orleans, 1B rue de la Ferrolerie, F-45071 Orleans Resume : Solid Oxide Fuel Cells (SOFC) are an efficient system of energy production minimizing greenhouse emissions. The optimization of constituent materials and their methods of fabrication should reduce the operating temperature while maintaining power performance and increasing durability.
The aim for decreasing the working temperature from 1000°C to 700°C can be reached by the reduction of the cell size and, more precisely, by the reduction of the electrolyte thickness down to 5 µm. Vacuum deposition techniques are the best tools to obtain thin, dense, homogeneous, low gas permeability films.
The cubic 8YSZ (8%mol yttria stabilized zirconia in cubic structure) phase which is the most widespread electrolyte material used at the present time, was deposited by KrF excimer PLD from a 8YSZ ceramic target and reactive DC magnetron sputtering from a Zr/Y metallic target. Deposition rates, chemical compositions, morphologies and crystallographic structures are considered for both techniques in the aim to compare the coating properties for obtaining electrolyte-compatible coatings. | R2 6 |
| 12:30 | LUNCH | |
| 14:00 | Laser Induced Forward Transfer of ZnO and TiO2 using double ultrashort pulses Authors : E.L. Papadopoulou(1), E. Axente(2), E. Magoulakis(3), G. Tsibidis(1), C. Fotakis(1,3) and P.A. Loukakos(1) (1)Foundation for Research and Technology - Hellas, Institute of Electronic Structure and Laser, P.O. Box 1385, 71110 Heraklion, Greece. (2) Lasers Department, National Institute for Lasers, Plasma, and Radiation Physics, P.O. Box MG 36, RO-77125, Bucharest-Magurele, Romania (3) Physics department, University of Crete, P.O. Box 2208, 71409 Heraklion, Greece. Resume : Laser Induced Forward Transfer (LIFT) has been used to transfer ZnO and TiO2 from a transparent substrate onto Si. The source used for the transfer was an amplified Ti:Sapphire laser (λ = 800 nm, 1 kHz repetition rate). The pulse duration was measured using autocorrelation to be 100 fs. The laser pulses were passing through a Pockels Cell and the repetition rate was scaled down to 1 Hz. The target – substrate pair was placed in a miniature vacuum chamber, at a distance of 100μm, which was pumped down to a pressure of 10-2 mbar. A Michelson Interferometer was used to create two pulses of equal intensity with varying time delay. The size and the morphology of the transferred dots were studied in respect to the time delay. It was found that the morphology of the transferred films was not depending on the time delay. In contrast, the diameter of the dots was found to significantly increase with the time delay for delays shorter than 500 fs. For longer time delays, the diameters were reaching a plateau and thereafter remaining constant. The results are discussed in terms of the ultrafast primary processes occurring in the thin films following excitation by the ultrashort laser pulses. | RPI 1 |
| 14:00 | High performance waveguides written in heavy metal oxide glass. Authors : A. Ferrer (1), R. Osellame (2), A. Ruiz (1), E. Cantelar (3), G. Cerullo (2), J. Solís (1) (1) Laser Processing Group, Instituto de Óptica, Consejo Superior de Investigaciones Científicas (C.S.I.C.), Calle Serrano 121, 28006 Madrid, Spain (2) Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci, 32, 20133 Milano, Italy (3) Departamento de Física de Materiales, C-IV, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain Resume : In this work we report the femtosecond laser writing of low-propagation-loss waveguides in Nd:doped (Nd2O3 at 1% wt.) 80TeO2-5TiO2-15Nb2O5 (molar concentrations) heavy metal oxide glass. Due to the nature of the matrix, this material shows very low phonon energies, what makes it very suitable for the production of active waveguides. On the other hand, the large hyper-polarizability of its constituents also leads to very large linear and non linear refractive indices. This feature hampers the laser inscription of high performance guiding structures due to spherical aberration and non linear propagation effects.
In order to determine the best processing conditions several parameters such as scanning speed, pulse energy and repetition rate have been analyzed. For low repetition rates (kHz regime), the transformed regions do not show a positive refractive index change while for repetition rates in the 100´s of kHz range, guiding is achieved as a consequence of a collateral densification in the vicinity of a damaged region located at the focal volume. For intermediate repetition rates, an optimal processing window was found (≈ 250 kHz) for which a positive refractive index change is induced in the focal region. Under these conditions and by optimizing the other processing parameters, we have produced waveguides with propagation losses below 0.5 dB/cm. The characterization of their active spectroscopic properties is now underway. | RPI 2 |
| 14:00 | Direct laser printing for high efficiency silicon solar cells fabrication Authors : G. Poulain (1), C Boulord (1), D Blanc (1), A Kaminski (1), M Gauthier (2), Y Pellegrin (3), M Lemiti (1) (1) : Université de Lyon; Institut des Nanotechnologies de Lyon INL-UMR5270, CNRS, INSA de Lyon, Villeurbanne, F-69621, France (2) : PHOTOWATT International S.A.S., 33 Rue Saint Honoré, 38300 BOURGOIN-JALLIEU - France (3) : SEMCO Eng., 625, rue de la Croix Verte - Parc Euromédecine, 34196 Montpellier Cedex 5 - France Resume : Silicon solar cells still require cost reduction and improved efficiency to become more competitive. New architectures can provide a significant increase in efficiency, but today most of the approaches need additional processing steps. In this context, laser processing offers a unique way to replace technological steps like photolithography that is not compatible with the requirements of the photovoltaic industry.
Selective ablation of dielectric with laser light is studied to open locally antireflection and passivation coatings at the front surface of silicon solar cells in order to take electric contacts. At the same time localised thermal effects induced by laser can be used favourably to activate or re-organise dopants that are present in the emitter. This paper proposes to investigate the influence of a nanosecond UV laser on phosphorous doped silicon emitters. Different crystalline silicon wafers with SiN layer and various doping concentrations (from 4x1019cm-3 to1020 cm-3) will be used. The interaction of the UV light with silicon will be characterised by optical and scanning microscopy, secondary-ion mass spectroscopy, sheet resistance cartography and I(V) measurements. Results will be apply to the fabrication of selective emitter solar cells that require high doping level in the electric contact areas and low doping concentration elsewhere. The process is potentially self- aligned and well suited to electroless or electrolytic metal contact deposition. | RPI 3 |
| 14:00 | Direct laser printing of polymer/CNT nanocomposites for gas sensing applications Authors : Christos Boutopoulos, Christos Pandis, Polycarpos Pissis, Ioanna Zergioti National Technical University of Athens, Physics Department, Zografou Campus, Greece, 15780 Resume : This work presents our recent results on direct laser printing of various polymer/CNT nanocomposite materials. The Laser Induced Forward Transfer (LIFT) technique is a rapid prototyping method allowing the effective deposition of materials at high spatial resolution. The LIFT experiments were carried out using a pulsed Nd:YAG laser (266 nm wavelength, 4 ns pulse duration) and a high power imaging micromachining system.
Laser irradiation of composite target materials, such as Poly(acrylic acid)/CNT and Polyvinylpyrrolidone/CNT, enabled dry deposition of well resolved composite pixels onto glass substrates. The dispersion of the CNT into the deposited composite pixels was investigated by transmission electron microscopy. The LIFT technique was also employed for the accurate deposition of polymer/CNT composite pixels onto aluminium microelectrodes for the fabrication of chemical sensors based on polymer/CNT compounds. The deposited composite pixels presented high electrical conductivity that makes these layers candidates for chemical sensing through amperometric measurements. The developed sensors have been characterized for various water and volatile organic compound (VOCs) concentrations.
The use of LIFT in the deposition of the sensitive composite layers allows the great flexibility of both the composite material and the pattern size which may vary between 10 and 250 μm. This simple and direct printing process can be applied for the deposition of a wide range of polymer/CNT composite materials and will help scientists to produce multianalyte chemical sensors and organic electronics based on the fascinating properties of the CNT. | RPI 4 |
| 14:00 | Fabrication of micro-channels in fused silica using laser induced backside wet etching (LIBWE) method Authors : B. Papdi, T. Csizmadia, Cs. Vass, G. Szabó and B. Hopp* Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dóm tér 9, Hungary, *Hungarian Academy of Sciences and University of Szeged, Research Group on Laser Physics, H-6720 Szeged, Dóm tér 9, Hungary Resume : Micromachining of transparent materials using indirect laser-based methods is an important research area nowadays. The developed techniques make the introduction of several new procedures possible in the micro-fluidics and micro-optical element fabrication. In this paper we investigated the main parameters of micro-channels produced by laser induced backside wet etching (LIBWE). 1 mm thick fused silica plates were applied as targets and saturated naphtalin-methylmethacrylate solution was the absorbing liquid. An ArF excimer laser beam (λ=193 nm, FWHM=20 ns) was focused onto the liquid-solid interfaces by a quartz cylindrical lens having 5 cm focal length. The number of pulses was varied between 0 and 8000. The applicable laser fluence was limited by the crack generation into the fused silica during the irradiation. The width and depth of the etched 2 cm long channels were measured by a surface profiler and plotted in the function of the pulse number. It was found that the maximum channel depth was 29 μm reached at 8000 pulses while the width did not changed significantly (≈40 μm) when increasing the number of pulses in the investigated range. The morphology of the bottom and wall of the channels was investigated by scanning electron microscope. The long-term motivation of our experiments is to apply our micro-channels in micro-fluidics for directed moving of living cells, biological and chemical solutions. | RPI 5 |
| 14:00 | FABRICATION OF POLYANILINE BIOSENSORS USING THE LASER INDUCED FORWARD TRANSFER PROCESS Authors : M. Kandyla, G. Tsekenis, P. Dimitrakis, S. Chatzandroulis, C. Pandis, I. Zergioti Physics Department, National Technical University of Athens, 9, Iroon Polytechniou, 15780 Athens, Greece Resume : Conducting polymers offer an attractive alternative to inorganic technology due to properties such as flexibility, low cost, light weight, and ease of processing. Applications based on organic conductors include, among others, chemical and biological sensors. Polyaniline is one of the most commonly used conducting polymers due to its high conductivity, excellent environmental stability, and ease of preparation.
We report the fabrication of polyaniline patterns for microbiosensor applications. The practical use of polyaniline is hindered by its mechanical properties and its poor solubility in most common organic solvents. In this work, polyaniline films are printed in the solid phase by Laser Induced Forward Transfer (LIFT) directly in between aluminum electrodes lying on a glass substrate. LIFT provides a versatile, economic, precise, non-contact way of thin-film deposition. By using LIFT, a laser pulse transfers a selected area of a thin film, from a transparent support on which the film has been deposited, onto a substrate placed in parallel and at a short distance to the film support. The removal of the selected area is achieved through localized interaction of the focused laser beam with the thin film and the process allows for excellent size control of the transferred area, as well as repeatability and miniaturization.
To apply solid-phase laser printing, aniline is in situ polymerized on quartz substrates and a nanosecond laser is used to transfer selected areas | RPI 6 |
| 14:00 | Improvement in semiconductor laser printing using sacrificial protecting layer for Organic Thin-film Transistors fabrication Authors : Ludovic Rapp1, Anne Patricia Alloncle1, Matthias Nagel2, Thomas Lippert3, Philippe Delaporte1 1 Laboratoire LP3 (Lasers, Plasma et Procédés Photoniques) - UMR 6182 CNRS - Université de la Méditerranée - Campus de Luminy C917, 13288 Marseille Cedex 09, France 2 Empa, Swiss Federal Laboratories for Materials Testing and Reasearch, Laboratory for Functional Polymers, Überlandstrasse 129, 8600 Dübendorf, Switzerland 3 Paul Scherrer Institut, General Energy Research Department, 5232 Villigen PSI, Switzerland Resume : The interest in organic thin-film transistors (OTFT) has recently been increased considerable because they offer unique opportunities in low-cost microelectronics. Laser-based processes offer versatile alternatives for the deposition of thin films in organic devices operating on flexible supports where usual techniques cannot be used due to a lack of solubility or in the case of complex device architectures fabrication.
Laser-Induced Forward Transfer has been used to deposit OTFTs using oligomer semiconductors such as distyryl-quaterthiophenes (DS4T) as active layer. The dynamics of the process have been investigated by shadowgraphic imaging for nanosecond and picosecond lasers on a time scale from the laser irradiation pulse to 1.5 µs. We have studied the transfer mechanism and determined the velocity of the material. An improvement of the process has been achieved using a sacrificial protecting layer, i.e. gold or triazene polymer (TP) layer, during the ejection. The triazene layer provides high laser absorption and a very low level of contamination of the transferred material. The TP has also a very low ablation threshold, resulting in a low thermal impact on the sensitive material. The transfer, i.e. the deposition and the electrical performances of the OTFTs is improved by the application of the TP. Functional OTFTs have been fabricated, and the morphology and thickness of the deposits have been investigated by optical, scanning electronic and atomic forces microscopies. | RPI 7 |
| POSTER SESSION I - Laser direct processing and synthesis : Magdalena Nistor, Richard Haglund, Chantal Leborgne, Eric Millon | ||
| 14:00 | Laser-induced backside dry etching of transparent materials having significantly different thermal parameters Authors : T. Csizmadia, T. Smausz, Cs. Vass and B. Hopp* Department of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged, Dóm tér 9, Hungary, *Hungarian Academy of Sciences and University of Szeged, Research Group on Laser Physics, H-6720 Szeged, Dóm tér 9, Hungary Resume : The laser-induced backside dry etching (LIBDE) method is a well-tried technique for micromachining of transparent materials. A thermal model was suggested to theoretically explain the etching processes, which describes the LIBDE procedure quite well, however it needs further experimental evidences. Therefore in this paper the dependence of the main etching parameters on the thermal properties of the substrate material was investigated. The sample materials: fused silica, glass, polimethyl-metacrylate and sapphire were selected due to the significant difference in their thermal data. The target plates were coated by 110 nm thick silver layer (absorber) by vacuum evaporation method. The metal films were irradiated perpendicularly trough the transparent materials by a focused dye laser beam (λ = 553 nm, FWHM = 20 ns). The illuminated area was 0.12 mm2, while the fluence was varied from 300 to 2100 mJ/cm2 and measured shot by shot. After the irradiation the remnant metal layer was removed and the etched holes were measured by a surface profiler. It was found that for each studied material the etch depth increased quasi-linearly when increasing laser fluence in the investigated range. The threshold fluence values were also determined. Theoretical thermal calculations were performed using the physical properties of the target materials and the experimental parameters as input values. The comparison showed a good agreement between the results of the calculations and the experiments. | RPI 8 |
| 14:00 | Polymer spatially controlled micropatterning for cellular behavior study Authors : V. Dinca1 *, A. Palla-Papavlu1, I. Paraico2, M. Dinescu1 NILPRP, National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-16, Zip RO-077125, Magurele, Bucharest, ROMANIA Tel. 004021 457 44 14 2 Department of Biophysics and Cell Biotechnology,“Carol Davila” Medical University, P.O.Box 35-43, Bucharest, Romania *Corresponding author: dinali@nipne.ro Resume : Simple and effective methods to functionalize glass surfaces that enable polymer micropatterning and subsequent spatially controlled adhesion of cells are reported in this paper. The methods involve the potential of two existing laser based techniques, namely laser induced forward transfer (LIFT) and matrix assisted pulsed laser evaporation (MAPLE) to achieve polymer patterning in a single step onto repellent substrates (i.e. poly(ethylene glycol) (PEG)). Both approaches were used to produce micron-size PEI- patterns alternating with cell-repellent areas. Topographical cues, independent of biochemistry, generated by LIFT and MAPLE may have significant effects upon cellular behavior. The effects of the substrate topography on the ability of cells to orient themselves, migrate, and produce organized cellular arrangements were investigated. | RPI 9 |
| 14:00 | Study of liquid deposition during laser printing of liquids Authors : A. Patrascioiu, M. Duocastella, J.M. Fernández-Pradas, J.L.Morenza, P.Serra Universitat de Barcelona, Departament de Física Aplicada i Òptica, Martí i Franquès 1, E-08028 Barcelona, Spain Resume : Laser induced forward transfer (LIFT) is a well known laser direct-writing additive technique that offers the possibility of creating a diversity of micropatterns through the deposition of a wide spectrum of materials in both solid and liquid state, such as conductors, dielectrics or biomolecules in a solution. When applied to liquids, LIFT technique consists in the deposition of microdroplets of a solution through liquid transfer from a donor liquid film to a solid receptor substrate by means of the action of a laser pulse. The technique has proven to offer a high spatial resolution, control and reproducibility. It also has provided an ideal way to transfer complex materials by allowing the laser interactions to affect only a localized region of the liquid, thereby propelling the majority of the desired material to the receiving substrate without harm. However, one of its main drawbacks stays in the preparation of the donor liquid film, being generally hard to obtain reproducible films in terms of stability and thickness uniformity. This is clearly an aspect that diminishes the potential industrial applications of the technique.
To avoid the negative effects associated with the preparation of the liquids in thin film form, a new laser transfer technique for printing transparent liquids has been developed, which involves the use of a transparent liquid reservoir in the place of the liquid thin film. Instead of focusing on a donor thin film, a femtosecond laser pulse is strongly focused underneath the free surface of the liquid, where by a non-linear transfer mechanisms the pulse is being absorbed. This results in the generation of a bubble which will cause the propulsion of the liquid out of the surface, leading to material deposition on a substrate situated in close proximity to that surface.
A study of the influence of the main laser parameters (laser pulse energy, laser focusing depth…) on the morphology and the dimensions of the printed liquid droplets has been carried out. The results showed clear correlations between the size and form of the deposited droplets and the mentioned laser parameters. These correlations helped finding the optimum conditions at which the highest degrees of reproducibility are obtained. | RPI 10 |
| 14:00 | Thin films of biocompatible polymers for controlled drug delivery deposited by Matrix-Assisted Pulsed Laser Evaporation Authors : Irina Alexandra Paun1*, Valentin Ion2, Antoniu Moldovan2, Maria Dinescu2 1Faculty of Applied Sciences, University Politehnica of Bucharest, RO-060042, Romania 2National Institute for Laser, Plasma and Radiation Physics, RO-077125, Magurele, Bucharest, Romania * Corresponding author; e-mail: irina.paun@physics.pub.ro Resume : Within the last years, controlled drug delivery is considered to be the optimum way to administrate drugs. In this work, we used Matrix-Assisted Pulsed Laser Evaporation (MAPLE) to develop thin films of biocompatible polymers (polyethylene glycol, poly (lactide-co-glycolide)) for controlled drug release in medical implants. Film deposition was carried out with a Nd: YAG laser working at 266 nm, at fluences between 0.1-1.2 Jcm-2. The films were deposited on quartz plates and Si wafers, for post-deposition analysis. The morphology of the films was investigated by Atomic Force Microscopy (AFM), showing smooth surfaces and uniform covering of the substrates. The chemical properties of the films were investigated by Fourier transform infrared spectroscopy (FTIR). Importantly, no evident chemical modifications of the MAPLE deposited layers with respect to the drop-casted films were detected. The refractive index of the thin films was determined by ellipsometry, the compatibility with the optical characteristics of biological media being discussed. The wetting properties of the films for different biological fluids were examined by contact angle measurements. Furthermore, UV-VIS spectrophotometry was used for probing the potential of the polymeric films as drug delivery systems. In all, the results indicate that MAPLE deposited polymer thin films are suitable candidates for controlled drug delivery implants. | RPI 11 |
| 14:00 | Photopolymerization Induced Assembly of Nanoparticles Authors : Abigail T. Juhl, John D. Busbee, John J. Koval, Lalgudi V. Natarajan, Vincent P. Tondiglia, Richard A. Vaia, Timothy J. Bunning, Paul V. Braun Resume : Nano-scale three-dimensional structures are commonly fabricated in one-step with relatively few defects via holography by using photoresist as a template to record the spatially periodic intensity formed by a laser interference pattern. However, it remains challenging to efficiently assemble nanoscale species into complex structures for functional materials on the macro-scale. In this work, we demonstrate a multi-component photoresist that may be used for one-step patterning of an arbitrary material into the desired high or low intensity regions of an interference pattern. We specifically, demonstrate the assembly of 25 nm silica nanoparticles into a layered structure with a one micron periodicity within a pentaerythritol triacrylate/ 1-vinyl-2-pyrrolidinone matrix using a 532 nm laser. Transmission electron microscopy is used to measure the effect that exposure time, exposure power, nanoparticle concentration, periodicity, and nanoparticle size have on the assembly of the nanoparticles. Brief discussions on adding reactive functionalizations to the silica as a means of positioning the nanoparticles into regions of high or low intensity will be included. | RPI 12 |
| 14:00 | Parametric studies on iron-carbon composite nanoparticles synthesized by laser pyrolysis for increased passivation and high iron content Authors : F. Dumitrache, I. Morjan, C. Fleaca, R. Birjega, R. Alexandrescu National Institute for Lasers, Plasma and Radiation Physics, Laser Department, Laser Photochemistry Laboratory PO Box MG-36,R- 077125 Bucharest Romania E. Vasile, S.C. Metav C.D. , C.A. Rosetti 31 st., R-020011, Bucharest Romania, V. Kuncser, National Institute of Materials Physics, PO Box. MG-7, R-077125, Bucharest Romania Resume : Iron/ iron carbide core and carbon shell nanoparticles with improved magnetic properties were successfully synthesized by laser pyrolysis. As iron and carbon precursors, iron pentacarbonyl and pure or argon-diluted acetylene /ethylene mixtures, respectively were used. Ethylene plays also the role of the laser energy transfer agent towards the reactive mixtures. The aim of the present optimization is the improvement of the magnetic properties of the nanomaterials by the increase of the iron percent in powders simultaneously to the maintaining of the protective character of the carbon coverage of nanoparticles. The chemical content and the crystalline structure were monitored by EDX and XRD techniques. In a first study, the content of acetylene as carbon source was diminished from 75% to 0%. Consequently the percent iron increased from 10 at% to 28 at% while oxygen remained relatively constant (around 5 at %). XRD confirmed the absence of iron oxide, but also the crystallinity improvement of Fe3C- cohenite. In a second step, only diluted (with argon) ethylene was used (maximum 87.5%). In this case, EDX analysis demonstrated an increase of iron to 46 at%. An optimum 50% carbon source dilution was found (further increase of carbon dilution is leading to an increase of the oxygen content in powder – to about 13%). Finally, an optimum laser power was found at 75W. Above this value, the carbon content increases and below it, superficial oxidation increases through the diminishing of the carbon shell. The most relevant samples were analyzed by TEM and Mossbauer spectroscopy and from the point of view of their magnetic properties. | RPI 13 |
| 14:00 | ABOUT GRAPHENE RIBBONS DEVELOPMENT IN LASER SYNTHESIZED NANOCARBON Authors : L. Gavrila Florescu1, E. Vasile2, I. Sandu1, I. Soare1, E. Popovici1, R. Ianchis3, C. Luculescu1, E. Dutu1, R. Barjega1, I. Morjan1, I. Voicu1* 1National Institute for Lasers, Plasma and Radiation Physics, P.O. Box MG-36, Bucharest, Romania 2 METAV, 16-18 Zapada Mieilor St., 71529 Bucharest, Romania 3Institute of Chemical Research, 202 Splaiul Independentei, CP 15-159, 76250 Bucharest, Romania Resume : The versatile method of laser induced pyrolysis of hydrocarbon-based mixtures allows obtaining carbon nanopowders with morphologies characterised by turbostratic or fullerene-structure up to long developed graphene ribbons. In-situ functionalized during synthesis process, these carbon nanopowders could fulfil the requirements of specific applications. The well-developed graphene ribbons composing the synthesized carbon nanopowders proved to be of interest for hybrid polymer-based composites with foreseen electrical properties or high mechanical resistance. The work is presenting preliminary studies with the goal to extend the weight of long graphene ribbons in carbon black’s composition. Investigations by transmission electron microscopy and its associated techniques (EDX, SAED, EELS), X ray diffraction (XRD) and dynamic light scattering (DLS) methods revealed the existence, as a majoritary constituent, of graphene ribbons composed by up to 10-15 graphene layers, spaced at ~ 3.5-3.7 Å and with length of tens of nanometers. The exploratory samples used to study the development of this specific structure were investigated both by the variation of experimental parameters and gas composition and the obtained polymer-based nanocomposites using these carbon nanopowders showed promising results for the specific applications. | RPI 14 |
| 14:00 | Excimer laser accelerated synthesis of morphology and size controlled ZnO nanocrystals Authors : K. D. G. Imalka Jayawardena, James Fryar, S. Ravi P. Silva and Simon J. Henley Nanoelectronics Centre, Advanced Technology Institute, University of Surrey, Guildford, Surrey, GU2 7XH, United Kingdom Resume : The synthesis of ZnO nanocrystals is reported using a hydrothermal chemical growth technique combined with 248 nm nanosecond excimer laser annealing at fluences in the range 0 – 390mJ/cm^2. The effect of the annealing in controlling the morphology of the nanocrystals is investigated using optical spectroscopy and electron microscopy characterization. Laser annealing is shown to allow control of the crystal morphology from nanoparticles to nanorods as well as to modify the size distributions. A laser heating model is introduced in order to clarify the effect of the irradiation. The results indicate that not only does the laser accelerate the growth of nanocrystals, but can also produce crystals with a narrow size distribution possibly via photothermal size selection. Subsequently, these nanocrystals are used to grow narrow ZnO nanorods through further hydrothermal growth. | RPI 16 |
| 14:00 | Formation and characterization of Ag and Au nanoparticles created by pulsed laser ablation in liquid media Authors : A.S. Nikolov, N.N. Nedyalkov, I.G. Dimitrtov, P.A. Atanasov Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, 1784 Sofia, Bulgaria Corresponding author: e-mail: anastas_nikolov@abv.bg Resume : Pulsed laser ablation of Ag and Au targets immersed in different liquids (double distilled water or acetone) is used to synthesize metallic nanoparticles (NPs). The targets are irradiated for about 10 min with laser pulses delivered by a Nd:YAG laser system at different wavelengths from the fundamental up to the fourth harmonic (λ = 1064, 632, 355, 266 nm respectively). The ablation process is performed at a repetition rate of 10 Hz and with pulse duration of about 17 ns. The laser fluence is changed from several J/cm2 to tens of J/cm2. The suspensions obtained are investigated by optical transmission spectroscopy in the near UV and in the visible and by DSL (dynamic light scattering) technique to get estimation of the size distribution of the NPs produced. The NPs shape and morphology are evaluated from TEM images. The structure is studied by XRD and the chemical composition by EDX, respectively. The aging of the suspensions is examined (without adding any surfactants). Moreover, the influence of the laser irradiation of the suspension on the aging of the NPs, its morphology and size distribution, is studied. The characteristics of the experimentally obtained transmission spectra of the colloids produced are analyzed by a theoretical model based on the multiparticle Mie scattering theory. A discussion on the NPs formation mechanism is also presented. | RPI 17 |
| 14:00 | Improved exhaust system for minimizing the agglomeration of Fe-based nanoparticles in laser pyrolysis processes Authors : F. Dumitrache, E. Popovici, I. Morjan, I. Sandu, C. Fleaca, C. Luculescu, R. Alexandrescu National Institute for Laser, Plasma and Radiation Physics, Laser Department, Laser Photochemistry Laboratory, PO BOX MG-36, Atomistilor 409 st. R 077125, Bucharest, Romania G. Prodan, V. Ciupina, Ovidius University of Constanta, Mamaia Avenue 124, R 900527, Constanta Romania C. Nicolicescu, University of Craiova, Faculty of Engineering and Management of Technological Systems, Calugareni 1 st., R 220037, Drobeta Turnu Severin, Romania Resume : The laser pyrolysis is particularly suitable as synthesis technique for the obtaining of nanoparticles with well defined dimensions. These are determined by the reaction zone where the laser beam is orthogonally crossing the reactive gas flow. A tubular nozzle system assures the laminar flow of the reactive gases which are confined to the flow axis by an Ar flow. In spite of the sudden cooling suffered at the exit of the reaction zone (temperature gradients of about 105 0C/sec) , freshly nucleated nanoparticles are still agglomerated. The present study reports of an improved exhaust system, consisting of a nozzle with truncated conical inner section. Both gas mixture and reaction products are obliged first to enter the low-dimension (0.5- 1.5 mm) pinhole and then suddenly to expand. For the laser synthesis of iron oxide and core-shell iron-iron oxide nanoparticles, optimum pinhole diameter and its position relatively to the reaction zone were studied. Different analysis techniques (such as EDX, SAED, TEM and XRD) were used in order to evaluate the produced nanopowders versus similar ones, obtained by laser pyrolysis equipped with standard exhaust systems. For nanopowders dispersed in ethanol (100 mg/l concentration), DLS measurements were performed. The mean cluster diameter decreases from 750-550 nm to 320-280 nm by using a nozzle system with 0.7 mm pinhole diameter, located at a distance of 1.5 mm from the irradiation spot. | RPI 18 |
| 14:00 | Improvement of superconducting properties applying an electrical current during laser floating zone growth Authors : M.F. Carrasco and F.M. Costa I3N, Physics Department, University of Aveiro, 3810-193 Aveiro, Portugal V.S. Amaral CICECO, Physics Department, University of Aveiro, 3810-193 Aveiro, Portugal R.F. Silva CICECO, Glass and Ceramic Engineering Department, University of Aveiro, 3810-193 Aveiro, Portugal Resume : The new electrically assisted laser floating zone (EALFZ) technique was use to grow superconducting fibres of Bi2Sr2CaCu2O8 (BSCCO-2212). The application of an electrical current through the crystallization interface proved to advantageously modify the phase nature and texture of 2212-BSCCO polycrystalline fibres comparing to conventionally laser floating zone (LFZ) grown ones. The current application during the growth induces a selective and more intense ionic migration along the fibre axis. As a result, an increase in superconducting phase fraction and a decrease of residual melt were observed together with grain alignment intensification. Consequently, an improvement of Bi2Sr2CaCu2O8 fibre’s superconducting properties was observed, being the main outcome the improvement of the critical current density at 77K.
*Corresponding author. Phone: +351 234 378 111
E-mail address: flor@ua.pt (Florinda M. Costa) | RPI 19 |
| 14:00 | LASER NANOSTRUCTURING OF BI-LAYER METAL THIN FILMS Authors : S.E.Imamova, N.N. Nedyalkov, P.A. Atanasov Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko shousse 72, Sofia 1784, Bulgaria Resume : We present results on investigation of laser nanostructuring of a sandwich which consists of two different metal layers. The both thin films (gold and nickel), having different thicknesses, are consequently deposited by pulsed laser deposition technique on glass substrate. The overall thickness of the structure varies from 40 to 100 nm. The as-deposited structures are then annealed by nanosecond laser pulses produced by Nd:YAG laser system at wavelength of 355 nm. The dependence of the layer thicknesses, the laser fluence and the numbers of the pulses applied for annealing on the properties of the produced structures is investigated. By varying the processing conditions, the metal films can be decomposed into nanoparticles with wide range of sizes and different composition (ration of gold and nickel). Using the proposed method it is also possible to obtain alloyed nanoparticles which are composed by the two metals. The formation mechanism and the influence of the processing parameters are discussed. | RPI 20 |
| 14:00 | Small size metal oxide nanoparticles synthesized by laser ablation in water Authors : F. Barreca^a, N. Acacia^b, D. Spadaro^a, E. Barletta^a, G. Currò^a and F.Neri^b a) Advanced and Nano Materials Research s.r.l., Salita Sperone 31, I-98166, Messina, Italy b) Dipartimento di Fisica della Materia e Ingegneria Elettronica, Università di Messina, Salita Sperone 31, I-98166, Messina, Italy Resume : Metal oxide nanoparticles have been synthesized by pulsed laser ablation in distilled water (LAL). Metallic targets of titanium, indium and tungsten were irradiated with a second harmonic (532 nm) output of a Nd:YAG laser, varying the laser fluence and the ablation time. The as prepared nanocolloids samples have been examined and the effects of the ablation parameters on the morphological and structural properties of the grown nanostructures have been investigated by means of transmission and scanning electron microscopies, X-ray photoelectron spectroscopy and UV-Vis spectrophotometry. At all fluences a predominant presence (60-85%) of small nanoparticles of 2-5 nm was accompanied by larger size ones up to 200 nm depending on the material. The amount of particles per unit volume of the colloid increases regularly with the ablation time, supporting the scalability of the production technique. The oxidation state of the different nanoparticles has been determined, confirming the efficiency of LAL as a cheap and eco-sustainable way to produce this kind of nanostructures. | RPI 21 |
| 14:00 | Stainless steel nanoparticles and nanostructured films by ultrashort laser ablation Authors : T. Szörényi Department of Natural Sciences and Environmental Protection, College of Dunaújváros, 2401 Dunaújváros, PO Box 152, Hungary, and LaserSkill Ltd., Kálvária sgt. 24., H-6722 Szeged, Hungary Resume : It is widely assumed that nanostructured materials will come to dominate the structural applications of advanced materials as well. Despite the inherent limitation posed by the loss of tensile ductility with grain sizes much below 1 μm, the expectation is that steels with effective grain sizes in the nano range will result in exceptional properties via the Hall-Petch equation. The reality of this expectation can only be checked by measuring the properties of material prototypes. Ablation with sub-ps pulses is an appealing technique for production of nanoparticles and nanostructured prototype films in general. We follow this route, adding thereby a bottom-up approach to the existing toolbox of techniques devoted to the production of nanostructured steel alloys. We report on
- production of (stainless) steel nanoparticles and nanostructured films by ablation of a stainless steel target with temporally clean 700 fs @248 nm pulses of a hybrid dye/excimer system in vacuum and controlled atmospheres,
- the process window of nanoparticle production in terms of laser intensity,
- size distribution of the lateral dimensions and the height of the NPs as determined by TEM and AFM analyses of less-than-one-monolayer deposits, respectively,
- the dependence of the size distribution on film thickness, followed by SEM and AFM,
- the structure of the individual nanoparticles as revealed by the analysis of HRTEM images,
- and the chemical structure of the material as seen by XPS. | RPI 22 |
| 14:00 | Sub-100nm-Structuring using Optical Near Fields of Nanoparticles Authors : A.Kolloch1, J.Boneberg1, A.Plech2, P.Leiderer1 1-Department of Physics, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany 2-Institut für Synchrotronstrahlung, Karlsruher Institut für Technologie, 76021 Karlsruhe, Germany Resume : Nanoscopic particles can be used for structuring large surface areas with single laser pulses, employing the effect of optical near fields. This enhancement of the incoming electrical field of the laser allows modifying the underlying surface locally while keeping the surrounding area intact, if the appropriate laser power is applied.
In the case of dielectric spherical particles larger than or comparable to the wavelength of the illuminating laser pulse, the particle simply acts as a lens, focusing the light onto the surface underneath. The minimal focal spot which can be achieved in this way has a diameter of about λ/4.
Smaller features well below 100 nm can be obtained by using metallic nanoparticles. When illuminated by light, these nanoparticles act as antennas which provide a field enhancement that is confined to a very small space (down to a few tens of nanometres).
The field enhancement in the nanoparticles can be calculated using e.g. Mie-theory or DDA (Discrete Dipole Approximation) calculations. For single particles, the calculations are in good agreement with the experimental results. For ordered arrays of nanostructures, the field of the adjacent particles has to be taken in account.
We present several experimental examples for the application of the above-mentioned techniques for different size regimes and particle shapes and compare them to calculations. | RPI 23 |
| 14:00 | Growth of ZnO thin layers on polymeric substrates by innovative laser-assisted magnetron sputtering Authors : C.BECKER(a,b), J. PETERSEN(a,b), D. RUCH(a), A. DINIA(b) a.Department of Advanced Materials and Structures (DAMS), Centre de Recherche Public Henri Tudor, Rue de Luxembourg 66, L4221 Esch sur Alzette, Luxembourg b. Institut de Physique et Chimie des Matériaux de Strasbourg, (IPCMS) UMR 7504 CNRS-ULP, 23 rue du Lœss, BP 43, 67034 Strasbourg Cedex 2, France. claude.becker@tudor.lu Resume : Innovation in the field of Flexible Electronic Devices (FEDs) have been principally focused on the use of new materials (flexible polymeric substrates, conductive polymers, printable metals, organic semi-conductor, ...). Recently, one of the main scientific challenge in this domain is to obtain well-defined properties and structures to enhance FEDs performances. In this context, the development of new hybrid deposition techniques is considered as promising routes to reach innovative properties on temperature sensitive polymeric substrates.
The main development in this study consists in combining magnetron sputtering with a Nd-YAG laser to provide additional properties to ZnO thin films used as Transparent Conductive Oxide (TCO) deposited on poly(ethylene terephtalate) (PET) substrates. These both techniques are totally complementary, according to technical requirements and provide an enhancement in the control of surface/interface chemical composition, thin films structure and quality.
The effect of the laser irradiation parameters (wavelength and fluence) on films morphology and topography has been evaluated by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) respectively. Differences on chemical composition of the thin films have been highlighted by X-ray photoelectron spectroscopy (XPS) and Rutherford Backscattering Spectrometry (RBS). ZnO Structural information and crystalline quality have been assessed by X-Ray Diffraction (XRD) measurements. And finally, effect of laser on carrier concentration and mobility has been evaluated by Hall effect measurements. | RPI 24 |
| 14:00 | Fabrication of three-dimensional structures by direct laser writing Authors : K. Terzaki (1,2), A. Gaidukeviciute(1), E. Kasotakis (2), C. Fotakis (1,3), M. Vamvakaki (1,2), A. Mitraki (1,2), and M. Farsari (1). Resume : Two-photon polymerization technology is a nonlinear optical technique which allows the fabrication of high resolution three-dimensional (3D) microstructures. The polymerization process is initiated when the beam of an ultra-fast infrared laser is tightly focused into the volume of a transparent, photosensitive material. Two-photon absorption takes place within the focal volume; by moving the focused laser beam three-dimensionally within the material, complex 3D structures can be fabricated.
Here, we present our most recent work into the structuring by two photon polymerization of a series of novel organic-inorganic hybrid photosensitive materials as well as materials with metal-binding affinity. The latter ones have been subsequently functionalized with amyloid peptides which immobilize both metals and calcium phosphates without the need of intermediate layers.
Our results show that two-photon polymerization presents an interesting fabrication route for microstructured materials to be used as tissue engineering scaffolds. | RPI 25 |
| 14:00 | FUNCTIONALIZED GENTAMICIN- POLY(1,3-BIS-(P-CARBOXYPHENOXY PROPANE)-CO-(SEBACIC ANHYDRIDE)) 20:80 AND -POLY(D,L-LACTIDE) THIN FILMS FOR SUSTAINED DRUG RELEASE SYSTEMS Authors : R. Cristescu1, C. Popescu1, G. Socol1, A. Visan1, I.N. Mihailescu1, S.D. Gittard2, P.R. Miller2, R.J. Narayan2, A. Andronie3, I. Stamatin3, D.B. Chrisey4 1National Institute for Lasers, Plasma & Radiation Physics, Lasers Department, P.O.Box MG-36, Bucharest-Magurele, Romania 2Biomedical Engineering, University of North Carolina, Chapel Hill, NC, USA 3University of Bucharest, 3Nano-SAE Research Center, PO Box MG-38, Bucharest-Magurele, Romania 4Rensselaer Polytechnic Institute, School of Engineering, Department of Materials Science & Engineering, Troy, 12180-3590, NY USA Resume : Drug delivery needs quantitative temporal dispensing that must be coupled with ingestion (nasal, oral, dermal, etc.) and in vivo metabolic processing. The material construct required to achieve ideal therapeutic titration is beyond conventional organic and polymeric processing and herein we show how laser processing appears to be especially enabling for a complicated material system. We report on thin film deposition by MAPLE of two polymer-drug composite thin film systems. A pulsed KrF* excimer laser source (λ = 248 nm, τ = 25 ns, ν = 10 Hz) was used to deposit composite thin films of poly(1,3-bis-(p-carboxyphenoxy propane)-co-(sebacic anhydride)) 20:80 and poly(D,L-lactide), respectively, containing several gentamicin concentrations. Release of gentamicin from these MAPLE-deposited polymer conjugate structures was assessed. FTIR spectroscopy and Raman spectrometry were used to demonstrate that MAPLE-transferred materials exhibited chemical properties similar to the starting materials. We have also shown using AFM that MAPLE may be used to fabricate thin films of good morphological quality. The activity of gentamicin-doped films against Staphylococcus aureus bacteria was demonstrated using disk diffusion and drop testing. The influence of drug concentration over microbial viability will be presented. Our studies indicated that polymer–drug composite thin films prepared by MAPLE are suitable for controlled drug delivery as well as other medical applications. | RPI 26 |
| 14:00 | FUNCTIONALIZED PORPHYRINS DEPOSITION BY MATRIX ASSISTED PULSED LASER EVAPORATION Authors : R. Cristescu1, C. Popescu1, A. Popescu1, S. Grigorescu1, I.N. Mihailescu1, A.A. Ciucu2, S. Iordache3, A. Andronie3, I. Stamatin3, E. Fagadar-Cosma4, D.B. Chrisey5 1National Institute for Lasers, Plasma & Radiation Physics, Lasers Department, P.O. Box MG-36, Bucharest-Magurele, Romania, rodica.cristescu@inflpr.ro 2University of Bucharest, Faculty of Chemistry, Bucharest, Romania 3University of Bucharest, 3Nano-SAE Research Center, PO Box MG-38, Bucharest-Magurele, Romania 4Institute of Chemistry Timisoara of Romanian Academy, Department of Organic Chemistry, 300223, Timisoara, Romania 5Rensselaer Polytechnic Institute, School of Engineering, Department of Materials Science & Engineering, Troy, 12180-3590, NY USA Resume : The metalloporphyrin nanostructures with unoccupied orbitals in metals having symmetries eg(d(p)dxz and dyz were designed for new efficient catalysts mimicking natural enzymatic systems and for advanced optoelectronic devices, especially electrochemical sensors. The drawback confronted in this case is the deposition of the sensor structure to be used for porphyrins, but also for nucleotides, enzymes, phthalocyanines, etc. Conventional deposition techniques (e.g., Langmuir–Blodgett, dropcasting) face a weak interaction between the sensitive element and the support (carbon paste and gold electrode) that can interfere with the response. To avoid this difficulty, the necessity of implantation of the sensitive element onto support/substrate has emerged. We report the successful deposition by MAPLE of metallized nanostructured functional phenyl-substituted meso-porphyrins as thin films onto screen printed electrodes, silicon or quartz substrates. FTIR, Raman spectrometry, AFM were used to demonstrate that MAPLE-deposited Mn(III)-metalloporphyrin thin films were homogenous and structurally similar to the starting material. We studied the influence of laser fluence on both thin film structure and morphology. UV-vis, excitation and emission spectra were discussed in THF-water systems by varying the pH conditions. We investigated thin films of Mn(III)-metalloporphyrin MAPLE-deposited onto screen printed electrodes by cyclic voltammetry using dopamine and serotonin as analytes. | RPI 27 |
| 14:00 | THIN FILMS OF ARYLENEVINYLENE OLIGOMERS PREPARED BY MAPLE FOR APPLICATIONS IN NON-LINEAR OPTICS Authors : A. Stanculescu1, L. Vacareanu2, M. Grigoras2, M. Socol1, G. Socol3, F. Stanculescu4, N. Preda1, I. Ionita4 1 National Institute for Laser, Plasma and Radiation Physics, Str. Atomistilor, Nr. 409, PO Box MG-36, Magurele, Bucharest, 077125, Romania 2 P. Poni” Institute of Macromolecular Chemistry, 41 A Gr. Ghica Voda Alley, 700487-Iasi, Romania 3 National Institute of Materials Physics, Optics and Spectroscopy Laboratory, 105 bis Atomistilor Street, Bucharest-Magurele, P.O. Box MG-7, 077125, Romania 4Faculty of Physics, University of Bucharest, Str. Atomistilor nr.405, P.O.Box MG-11, Bucharest-Magurele, 077125 Romania Resume : The organic compounds show special properties associated with the conjugated system of electrons and the groups which are substituted to the aromatic nucleus, intercalated in the main chain or linked as side-chain to the polymer backbone. These compounds are intensively studied because of their large area of applications including the non-linear optics.
Two arylenevinylene oligomers containing good-electron donating groups (triphenylamine and N-alkylcarbazole) situated at the ends have been synthesized by Wittig condensation.
Matrix Assisted Pulsed Laser Evaporation (MAPLE) method using the 248 nm radiation of a KrF* excimer laser has been used to prepare thin, uniform oligomeric films on quartz, Ti and Si(100) substrates. The target is obtained by freezing in liquid nitrogen, the solution of the organic compound in chloroform. The thin film morphology was investigated by SEM and AFM and the optical properties by UV-VIS, FTIR and luminescence Spectroscopy. The thickness and the optical constants of the films have been evaluated by spectro-ellipsometry. We have also analysed the effect of the parameters characterizing the deposition process temperature (60-175 oC), pressure (0.05-0.2 torr), fluence (150-500 mJ/cm2) and pulses number (2000-6500) for the same solvent concentration on the properties of the films.
The fluorescence associated with the two photons absorption has been evidenced on both types of compounds. | RPI 28 |
| 14:00 | Characterization of polymer thin films obtained by pulsed laser deposition Authors : A. Palla-Papavlu*, V. Dinca, V. Ion, M. Dinescu NILPRP, National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-16, Zip RO-077125, Magurele, Bucharest, ROMANIA Tel. 004021 457 44 14 *Corresponding author: apalla@nipne.ro Resume : The development of laser techniques for the deposition of polymer and biomaterial thin films on solid surfaces in a controlled manner has attracted great attention during the last few years. Here we report the deposition of thin polymer films, namely Polyethilenimine (PEI), Polyisobutylene (PIB) and Polyepichlorhydrine (PECH) by pulsed laser deposition (PLD). PEI, PIB and PECH polymers were deposited on flat substrates (i.e. silicon and fused silica plates) using an ArF excimer laser (193 nm wavelength, FWHM = 30 ns) and a NdYAG laser (266nm, 355 nm wavelength).
The obtained thin films have been characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and spectroscopic ellipsometry (SE).
A discussion on the influence of the laser parameters such as wavelength, fluence and number of pulses on the morphology and chemical structure of the polymer layers obtained is made. Moreover, a comparison with films deposited by matrix assisted pulsed laser evaporation (MAPLE) has been made. The obtained results indicate that PLD method is potentially useful for the fabrication of polymer thin films to be used in applications including electronics, microsensor or bioengineering industries.
Keywords: PLD, polymer thin films | RPI 29 |
| 14:00 | Laser deposition of nanocomposites SnO2/polypyrrole and NiO/polypyrrole Authors : Dušan Kopecký, Department of Physics and Measurement, Institute of Chemical Technology, Prague, Czech Republic Martin Vrňata, Department of Physics and Measurement, Institute of Chemical Technology, Prague, Czech Republic Přemysl Fitl, Department of Physics and Measurement, Institute of Chemical Technology, Prague, Czech Republic Filip Vysloužil, Department of Physics and Measurement, Institute of Chemical Technology, Prague, Czech Republic Vladimír Myslík, Department of Solid State Engineering, Institute of Chemical Technology, Prague, Czech Republic Josef Náhlík, Department of Solid State Engineering, Institute of Chemical Technology, Prague, Czech Republic Jaroslav Hofmann, Department of Physics and Measurement, Institute of Chemical Technology, Prague, Czech Republic Resume : Thin layers (~200 nm) of nanocomposites SnO2/polypyrrole and NiO/polypyrrole have been prepared by laser depositions through 4th harmonics of Nd:YAG laser. Nanocomposites were synthesized by chemical process. Deposition parameters were as follows: wavelength of laser radiation λ = 266 nm, pulse duration 5 ns, energy fluence F = 0.02 to 0.6 J·cm-2. Deposition was carried out in a nitrogen ambient on polished silicon substrates. The mechanism of deposition method combines the Matrix Assisted Pulsed Laser Evaporation (MAPLE) for the deposition of organic matter and Pulsed Laser Deposition (PLD) for the deposition of inorganic substances, thus creates a new way for preparation of thin layers of nanocomposites in situ in one technological step. Chemical composition of the resulting layers is characterized using FTIR, Raman spectroscopy (monitoring changes in the structure of polypyrrole) and XPS (stoichiometry of oxides) and their morphology is studied using SEM for different energy of laser radiation. Results of the analyses show that the deposition around ablation threshold FTH preserve the structure of polypyrrole and the degree of conjugation of double bonds in its molecule remain intact. The obtained results are important for the further preparation of thin sensitive layers of chemical gas sensors based on nanocomposites. | RPI 30 |
| 14:00 | Thin films of Mg-Al Layered Double Hydroxides (LDHs) and their derived mixed oxides grown by laser techniques Authors : A. Matei, R. Birjega, A. Nedelcea, A. Vlad, M. Filipescu, D. Colceag, D. Ionita, C. Luculescu, M. Dinescu National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 76900 Bucharest-Magurele, Romania R. Zavoianu, O.D. Pavel University of Bucharest, Faculty of Chemistry, Department of Chemical Technology and Catalysis, 4-12 Regina Elisabeta Bd., Bucharest Resume : Layered double hydroxides (also known as hydrotalcite-type compounds - HT) are lamellar materials with layers positively charged (brucite layer) and anions trapped in the region between layers. Powdered layered double hydroxides (LDHs) have been widely studied due to their applications as catalysts, anionic exchangers or host materials, adsorbents for environmental contaminants and for the immobilization of biological materials.
As thin films, LDH are good candidates for novel applications as sensors, corrosion resistant coatings or components in electro optical devices. For these applications, lamellar orientation-controlled film has to be fabricated.
We report on the deposition of thin films by laser techniques (laser ablation PLD and matrix assisted pulsed laser evaporation MAPLE) starting from targets of Mg-Al LDHs and their derived mixed oxides. The ability of Mg-Al LDHs as a carrier for metallic particles (Ag, Ni) has been considered. Frozen targets containing 10% powder in water were used for MAPLE, while for PLD the targets consisted in dry-pressed pellets. For both deposition techniques ultraviolet light (266 nm) was used to irradiate the targets.
The structure and the surface morphology of the deposited films were tested by X-Ray Diffraction, Atomic Force Microscopy, Scanning Electron Microscopy and Secondary Ions Mass Spectrometry. The wetting properties were investigated by contact angle measurements. | RPI 31 |
| 14:00 | SPECTROSCOPIC DIAGNOSTICS OF LASER INDUCED PLASMA IN LIQUID Authors : N.V. Tarasenko, A.V. Butsen, Institute of Physics, National Academy of Sciences of Belarus, 68 Nezalezhnasti Ave., 220072 Minsk, Belarus Resume : Pulsed laser ablation (PLA) of solid samples submerged in liquid has been shown to have a great potential for fabrication of nanoparticles. As physical properties of plasma plume, such as species concentrations and temperature, directly affect the processes leading to particle synthesis, an improved knowledge of dynamics of the laser-induced plasma composition is important for the purpose of optimizing the conditions for synthesis of nanoparticles in liquids. In spite of the fact that, laser-induced plasmas in liquid are characterized by intense continuum emission spectra, spectroscopic techniques can be very useful for plasma characterization, especially in the case of double pulse laser ablation.
Characterization of the ablated plume was performed by the time resolved emission spectroscopy and gated intensified CCD imaging technique. Experiments were made by using a combination of two laser beams generated by pulsed Nd:YAG lasers (LOTIS TII, model LS2134), operating at 1064 nm (IR) and 532 nm (green), each with 45 mJ pulse in a 5-mm beam. The main features of generation and evolution of laser-induced plasmas in liquids have been studied. The double-pulse laser ablation mode has been shown to enhance an efficiency of nanoparticles formation and to increase an emission of atoms and ions from the plasma due to the increased ablation rate of the target material. The main parameters of the laser-produced copper and silver plasmas in liquids, such as temperature and density of atoms and electrons have been determined. The capabilities of pulsed laser ablation in liquids for synthesis of nanoparticles have been analyzed. | RPI 32 |
| 14:00 | MODIFICATION OF WC POWDERS WITH PULSED ELECTRICAL DISCHARGE IN LIQUIDS Authors : A.A. Nevar1, N.V. Tarasenko1, M.I.Nedelko1, N.N. Tarasenko1, E.I. Mosunov2, S.A.Kovaleva2, T.F.Grigoryeva3 1B.I. Stepanov Institute of Physics of National Academy of Sciences of Belarus, 68 Nezalezhnasty Ave., 220072 Minsk, Belarus 2The Joint Institute of Mechanical Engineering NAS of Belarus, 12 Akademicheskay Str , Minsk, 220072,Belarus 3Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of Russian Academy of Sciences, 18 Kutateladze, Str , Novosibirsk, 630128, Russia, Resume : The electric discharge technique, both with and without preliminary conventional mechanochemical milling has been applied to a treatment of tungsten powders (average particle diameter is about 2 microns) in liquid. X-ray diffraction was employed for phase identification of starting materials and reaction products. The powder morphologies were characterized by X by SEM.
The experiments showed that the processing of tungsten powders by electrical discharge in ethanol results in modification of morphology, phase composition and crystal structure of the parent particles. Formation of nano-sized (10 nm and less) particles of non-stoichiometric W3C carbide has been observed for mechanically non-activated powders. The formation of carbide phase was believed to occur via a complex process, involving rapid particle fracturing during electrical discharge, interaction of the fine particles with carbon atoms and free radicals generated by the decomposition of ethanol in the electrical discharge plasma, and thermally activated local diffusion of the carbon into the powder particles. For a powder preliminary subjected to a mechanochemical activation a surface carbonization of starting particles was more preferable. The possible mechanisms responsible for the observed modification of metallic powders are discussed.
The work has been supported by the Integral Program of the Siberian Branch of RAS under the Grant 138-T-09-CO-014 | RPI 33 |
| 14:00 | Multiscale surface texturing for endosseous implant applications using femtosecond lasers Authors : Alexandre Cunhaa,* Vitor Oliveira **, Rui Vilar* *Instituto Superior Técnico, Materials Engineering Department, Av. Rovisco Pais, Lisbon, Portugal 1049-001 **Instituto Superior Engenharia Lisboa, Rua Conselheiro Emídio Navarro N0 1, Lisbon, Portugal 1959‐007 Resume : The aim of the present work is to investigate surface texturing of medical grade Ti-6Al-4V alloy by femtosecond laser treatment in order to assess its potential to produce bio-inspired surfaces for osseointegration enhancement. The samples were treated using a Yb:KYW chirped-pulse-regenerative femtosecond infrared laser with a wavelength of 1030 nm and a pulse duration of 500 fs. The dependence of the surface topography and composition on the processing parameters was studied by scanning electron microscopy and X-ray photoelectron spectroscopy. In order to assess the wettability of the laser treated surfaces, static contact angle measurements using water and a protein solution as testing liquids were performed. By properly selecting the processing conditions surface textures at the nano or the micro scales or bio-inspired bimodal distribution surface roughness can be reproducibly produced. The laser treated surfaces present a time-independent hydrophobic response. In the presence of proteins the wettability increases with time. The difference in the wettability behaviour is related to the type of testing liquids as well as to the characteristics of the underlying laser treated surfaces. The different wettability responses of these surface structures may be used for protein adsorption or water molecule repellent. | RPI 34 |
| 14:00 | Nanostructuring of titanium by its ablation with short laser pulses in liquid environment Authors : E.V. Barmina1*, E, Stratakis2, C. Fotakis2, and G.A. Shafeev1 1 Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov street, 119991, Moscow, Russian Federation 2 Institute of Electronic Structure and Laser, Foundation for Research & Technology—Hellas, (IESL-FORTH), P.O. Box 1527, Heraklion 711 10, Greece. *corresponding author, e-mail: barminaev@gmail.com 1 Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38, Vavilov street, 119991, Moscow, Russian Federation 2 Institute of Electronic Structure and Laser, Foundation for Research & Technology—Hellas, (IESL-FORTH), P.O. Box 1527, Heraklion 711 10, Greece. Resume : The process of nanostructures (NS) formation on bulk Ti immersed into either water or ethanol is experimentally studied under its exposure to short laser pulses. Two types of lasers were used: either a KrF excimer laser emitting at 248 nm with pulse duration of 5 ps or a Nd:YAG laser emitting 150 ps pulses at the wavelength of 355 nm. Nanostructures were characterized by Field Emission Scanning Electron Microscopy (FE SEM), X-ray Photoelectron Spectroscopy (XPS), and Raman Spectroscopy. Density of NS and morphology depends on both the number of pulses and laser fluence. It is found that the formation of NS on Ti surface under its laser ablation in various liquids is accompanied by its strong visible coloration, and the corresponding color correlates with the NS morphology. Such coloration can be attributed to the plasmon oscillations of electrons in the NS. Possible applications of nanostructured titanium in medicine and biology are discussed. | RPI 35 |
| 14:00 | Laser ablation on sapphire and GaN using monolayer of microspheres Authors : Chii-Chang Chen, Chia-Hung Hou, Chia-Hua Chan, Alexis Fischer 1Department of Optics and Photonics, National Central University, 320 Jhung-Li, Taiwan 2Centrale de Proximité en Nanotechnologies de Paris Nord, Laboratoire de Physique des Lasers, Université de Paris 13 UMR-CNRS 7538, 93430 Villetaneuse, France Resume : We report the laser-assisted fabrication of air-holes on sapphire and GaN substrates using ArF and XeCl lasers. The monolayer of SiO2 and polystyrene microspheres is deposited on the substrates. The beam of excimer laser is focused on the substrate surface by the microspheres. Since the power density is larger than the threshold of the laser ablation of sapphire and GaN. The air-holes can be fabricated on the substrates. The patterns may enhance the extraction efficiency of GaN LEDs. | RPI 36 |
| 14:00 | Elastomechanical constants of TiN beams determined by laser vibrometry Authors : M. Birkholz, P. Kulse, K.-E. Ehwald, M. Kaynak, J. Drews, M. Fröhlich, U. Haak, K. Schulz, D. Wolansky, IHP – Leibniz-Institut für innovative Mikroelektronik, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany Resume : Elastically bendable structures with minimum feature dimensions in the micro- and nanometer range play an increasingly important role in microelectromical and nanoelectromechanical systems (MEMS and NEMS). Such devices will enable the fabrication of highly sensitive and minaturized sensors for different applications, which holds particularly for biomolecular sensing. The electromechanical characterisation of such structures may be performed by laser vibrometers, which allow for the monitoring of nanometric deflections with a time resolution in the ns range. We report on investigations of a microviscosimeter currently under development for continuous glucose monitoring in diabetic patients. The sensor operates by the principle of affinity viscosimetry, by which glucose concentrations to be determined are transformed into a viscosity signal. Fully integrated sensor chips were fabricated by standard semiconductor technology in the combined CMOS/BiCMOS pilot line of IHP. Only 50 nm thin, elastically bendable TiN beams were prepared from the metal layers used in the back-end-of-line (BEoL) process. The electromechanical characterisation was accomplished laser-interferometrically by using a vibrometer (HeNe, 633 nm). We demonstrate, how the built-in mechanical stress and elastomechanical constants of geometrically different TiN beams could be derived from measured deflection-voltage curves z(V) and their mechanical modelling. The technique is shown to allow complete wafer mappings. | RPI 37 |
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| LIFT and processing of organic materials : Peter Schaaf | ||
| 16:30 | Blister actuated laser induced forward transfer for printing organic materials Authors : Matthew S. Brown, Nicholas T. Kattamis, and Craig B. Arnold Resume : The ability to print a wide range of materials through laser induced forward transfer (LIFT) and other laser direct-writing techniques enables the formation of structures and material properties that cannot be produced through alternative means. In this presentation, we will introduce novel methods of shaping the laser-matter interactions in order to overcome limitations of direct-write processing for small scale and delicate materials. In particular, we develop the use of deformable absorbing layers and spatially-shaped laser intensity profiles to enable additional control over the local material properties in LIFT printing applications. A donor substrate is constructed with the material of interest deposited on a thick layer of polyimide attached to a glass microscope slide. The incident laser partially ablates the polyimide at the glass interface producing a trapped pocket isolating the ablation products from the material of interest. The induced pressure causes an expansion of the remaining polymer film leading to the formation of a blister which rapidly expands and propels the material of interest from the donor substrate. We present a comprehensive study of this blister actuated transfer process using in situ imaging, post-mortem analysis of transferred material, and numerical simulations. Through a detailed understanding of the transfer mechanism, we can use our models to simulate the effects of modifying the spatial profile of the incident laser and its effect on the transferred materials. Finally, we demonstrate the use of this technique in damage-free printing of organic semiconducting molecules for optoelectronic applications. | R3 1 |
| 17:00 | Laser Assisted Bioprinting of Biomaterials & Cells: Jet Formation Modeling, Experimental Results and Perspectives in Tissue Engineering Authors : S. Catros1, A. Souquet1, B. Guillotin1, C. Mézel2, L. Hallo2, JC Fricain1, F. Guillemot1 1- INSERM U577, University Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France 2- CELIA, University Bordeaux 1, 351 cours de la libération, 33405 Talence Cedex, France Resume : Parallel to inkjet printing and bioplotting, Laser Assisted Bioprinting (LAB) using Laser-Induced Forward Transfer (LIFT) is emerging as an alternative method to assembly and micropatterning of biomaterials and cells. LAB specificities concern mainly the absence of clogging and the capacity of printing fluids with a wide range of viscosity. In addition, as an optics-based method, a laser printing device can also be set up for targeting and shooting as well as marking, cutting, exciting, photo-polymerizing or else foaming materials. In this paper, we present results on LAB of human cells (osteoblasts, endothelial cells) as well as biomaterials (nano-sized HA synthesized by wet precipitation) giving an interest for 3D bone-like tissue building in combination with the physical phenomena of droplet ejection by LIFT.
First, a rapid prototyping workstation (NovaLase, S.A., Canéjan, France) equipped with an infra-red pulsed laser (30 ns pulse duration, 1064 nm wavelength, 1–100 kHz repetition rate) has been set up. A sophisticated 5–axe positioning system has been integrated to the workstation with the purpose of printing multi-color patterns and building 3D biostructures. The substrate is held with a (x, y, z) motorized micrometric translation stage whose resolution is 1 µm for (x, y) axis and 5 µm for the z axis. In order to achieve multi-color printing, a high resolution (1° angular resolution) motorized carousel with a loading capacity of 5 different ribbons has been designed. Substrate positioning system and carousel are held on the same vertical axis in the aim of varying focusing conditions without changing the gap distance between each other. Droplet generation from the ribbon surface is performed by driving the laser beam by means of a high speed scanning system composed of two galvanometric mirrors with a scanning speed reaching 2,000 mm/s, and a large field optical F-theta lens (F = 58 mm). Focal setting in the ribbon and (x, y, z) substrate positioning are carried out thanks to a CCD camera through the optical scanning system. Substrate positioning, carousel driving, video observation and pattern designs are monitored with dedicated software developed with Delphi® software.
Based on experiments, we propose a model to explain the ejection phenomena. According to the laser energy release in the absorbing layer we differentiate three ejection regimes which can be distinguished using a dimensionless parameter G. In each case a vapor bubble is formed at bioink – absorbing layer interface. Its expansion generates the bioink – air interface deformation and putting in motion. If the laser energy is not sufficient enough (G > G2) transfers could not occur unless the substrate is close to the target. This is defined as the subthreshold regime. If the laser energy is slightly higher (G1 < G < G2) the bubble expands, then collapses and finally a jet is formed. This regime is hence called jetting regime. The third regime which occurs when the laser fluence is much higher (G < G1) is the plume regime. The vapor bubble expands until it bursts. The ejection mode is closely related to the laser pulse energy and the vapor cavity dynamics, which depends on the bioink surface tension and kinematic viscosity and which can be described by the Rayleigh – Plesset equation.
Finally, droplets size (from 20 µm to 100 µm) has been controlled by monitoring laser focusing conditions and ink rheological properties (viscosity, surface tension). Droplets of 70 µm in diameter containing around 5–7 living cells per droplet has been obtained minimizing the dead volume of hydrogel around cells. We have shown LAB is suitable to print cells in close contact to each other, with a high cell concentration, according to a desired spatial organization. The viability and phenotype conservation of Human Osteo Progenitors (HOPs) have been shown on printed cells. The printing resolution achievable by LAB is consistent with the study of cell-to-cell, or cell-to-material interactions as well. In addition to cell transfer, we demonstrate the potential of LAB for creating well-defined patterns of nano-sized HA. Three-dimensional sequential printing of nHA and HOPs illustrated the possibility to build composite biological structures in 3D with a high resolution with the maintenance of osteoblastic cells biological properties after printing.
To conclude, LAB is a suitable technique for printing cells and biomaterials, and we have shown new insights about the ejection mechanism, what allows improving biological printing results (cell viability, resolution…). Future developments for tissue engineering applications will concern the use of our LAB workstation capacities for printing three-dimensional composite materials with a controlled internal architecture. | R3 2 |
| 17:15 | LASER PRINTING OF SEMICONDUCTING POLYMER MATERIAL FOR ORGANIC ELECTRONICS Authors : M. Makrygianni1, P. Dimitrakis2, P. Normand2, S. Chatzandroulis2, I. Zergioti1,* 1 National Technical University of Athens, Physics Department, Iroon Polytehneiou 9, 15780 Zografou, Athens, Greece 2 NCSR Demokritos, Institute of Microelecronics, Aghia Paraskevi 15310, Greece *Corresponding author: zergioti@central.ntua.gr Resume : We report our recent results on laser printed organic semiconductor materials by means of solid phase Laser Induced Forward Transfer process (LIFT). The aim of this work is the fabrication of hybrid organic/inorganic thin-film transistors with bottom-contact configuration. The LIFT experiments were carried out using a pulsed Nd:YAG laser (266 nm wavelength, 4 ns pulse duration) and a high power imaging micromachining system.
Using this direct laser printing technique, the regioregular poly-3-hexylthiophene (P3HT) was printed as the active layer of the transistor. More specifically, a polymer solution (P3HT/chloroform) was prepared and spin-coated on a quartz substrate (donor substrate). The receiver substrate consisted of Au/Ti source and drain electrodes patterned on dry silicon dioxide/p+-type Si substrate acting as the gate oxide and the gate electrode respectively. Upon irradiation, the polymer material (P3HT) was transferred and deposited in between the source and drain electrodes covering partially the electrodes. The distance between them defines the gate length of the transistor which varies between 40μm and 100μm. The morphology of the deposit was investigated by optical microscopy. Finally, electrical characterization measurements showed efficient field-effect action of the bottom gate on the organic channel. Transfer IDS-VGS characteristics exhibited well-defined subthreshold, linear and saturation regimes designating LIFT as a highly perspective technique for hybrid organic/inorganic transistor technology. | R3 3 |
| 17:30 | Multilayer Laser Printing for Organic Thin Film Transistors Authors : Ludovic Rapp1, Anne Patricia Alloncle1, Antonio Pereira2, Stephan Guy2, Christine Videlot-Ackermann3, Frédéric Fages3, Philippe Delaporte1 1 Laboratoire LP3 (Lasers, Plasma et Procédés Photoniques) - UMR 6182 CNRS - Université de la Méditerranée - Campus de Luminy C917, 13288 Marseille Cedex 09, France 2 Laboratoire de Physico-Chimie des Matériaux Luminescents, Université Claude Bernard Lyon 1, 69622 Villeurbanne cedex, France 3 CINaM (Centre Interdisciplinaire de Nanoscience de Marseillle) – UPR3118 - Campus de Luminy C913, 13288 Marseille Cedex 09, France Resume : The Laser-Induced Forward Transfer (LIFT) technique consists in removing a piece of a thin layer previously deposited on a transparent substrate and transferring it on another substrate using a pulsed laser.
Functional n- and p-channel OTFTs have been fabricated by LIFT in different configurations (Top and Bottom Gate with for the both Top and Bottom Contact). The broad nature of transferred patterns ranging from nanoparticle inks, metals to organic molecules such as oligomers and polymers confirms the potential of LIFT as a very versatile technique. The electrical characteristics of the devices show the feasibility and reproducibility of a laser direct writing technique for OTFTs.
This study is dedicated to demonstrate the possibilities of OTFTs laser printing from multilayer substrates. The substrates have been realized by Pulsed Laser Deposition, thermal evaporation under vacuum or spin coating. The transfer and deposition mechanism have been studied by time resolved shadowgraphic imaging. Operating devices have been characterized by current-voltage measurements. Morphology and thickness of the deposits have been investigated by optical microscopy, SEM and AFM. | R3 4 |
| 17:45 | Development of photocurable hybrid sol-gel materials applied to the fabrication of photonic devices. Authors : M. Oubaha, R. Copperwithe, C. McDonagh and B.D. MacCraith Optical Sensor Laboratory, National Centre for Sensor Research Dublin City University, Glasnevin, Dublin 9, Ireland Tel: 353 1 700 76 99, Fax: 353 1 700 80 21, e-mail: Mohamed.Oubaha@cu.ie Resume : Over the past decade, integrated optoelectronic devices have gained increasing importance with the rising demand for higher lightwave transmission capacity. One technology that can aggressively address the increasing need for integration of electro-optical components into miniaturised systems is that of lightwave circuits (LWC) based on optical channel waveguides fabricated from hybrid materials.
In this work we describe the development and characterisation of photocurable hybrid organic-inorganic sol-gel materials, and employ them to the fabrication of photonic devices for telecommunication, optical sensing and biosensing applications. This work will be divided into 2 parts. The first will be devoted to the material development and characterisation. The synthesis of photocurable sol-gel materials will be described and optical properties discussed and correlated to the material structure [1], and photoreactivity [2]. The second part will deal with the application of the developed materials to the fabrication of photonic and biosensor devices as well as three-dimensional structures. Fabricated photonic devices (e.g. optical waveguides and photonic crystals) will be characterised and discussed a well as arbitrary three-dimensional structures presented [3].
[1] M. Oubaha et al., Thin Solid Films 510 (2006) 334.
[2] R. Copperwhite et al., J. Non-Cryst Solid, 354 (2008) 3617.
[3] A. Ovisanikov,et al., ACS Nano, 2008, 2 (11), 2257. | R3 5 |
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