Laser material processing: from fundamental interactions to innovative applications

Resume : We present femtosecond laser-induced breakdown spectroscopy (fs-LIBS) methods for element detection with high spatial resolution and subsequent digital reconstruction of chemical images. Fs-lasers produce well defined ablation craters due to limited heat transfer out of the laser-matter interaction volume which is beneficial for high resolution LIBS imaging. Measurements were conducted using a fs-laser that is capable of producing 400 fs pulses at a wavelength of 1040 nm. Laser pulses at the fundamental or the second harmonic wavelength were focused on the sample by means of glass lenses or Schwarzschild microscope objective for plasma excitation. Samples were placed on a 2D translation stage and each site at the sample surface was measured by one laser pulse. Plasma radiation was detected in backwards direction. LIBS experiments were conducted on different samples: (a) commercial Cu grids (150 µm and 30 µm mesh) on Mn metal substrate, (b) Cu microdot arrays (dot size: e.g. 8 µm x 8 µm, thickness 60-300 nm) on Si wafer substrates produced by nanoimprint lithography, and (c) Cu thin films (thickness 35-500 nm) evaporated onto glass slides. Our results show accurate digital sample reconstruction from measured LIBS signals for the Cu grid and microdot samples. On the Cu thin films the ablated mass per single fs-pulse was around 10 fg which is equivalent to a Cu particle of radius 640 nm. Imaging experiments with another fs-laser (175 fs, 400 nm) produced similar results and individual Cu microdots of mass approx. 35 fg and equivalent particle radius 970 nm were detected. Our next LIBS measurements will be conducted using double-pulse fs laser excitation for even higher spatial resolution and lower sampled mass. Financial support by the Austrian Research Promotion Agency FFG is gratefully acknowledged (K-project PSSP 871974). We acknowledge M. Haslinger and Profactor GmbH for the preparation of Cu/Si samples.

Resume : Direct laser cladding refers to development of component by melting the material in the form of powder or wire and subsequently, deposition of the molten materials on a dummy substrate in a layer by layer fashion to achieve the near net shape using computer aided designing. The process may be applied to develop metals/alloys, metal matrix composite and intermetallics. In the present contribution, titanium aluminide (with the composition of Ti45Al5Nb0.5Si) based composite has been developed by direct laser cladding, where, TiC has been added as dispersoids in molten TiAl. Direct laser cladding has been conducted using a high power (3 kW) fiber optic delivered Nd:YAG laser (with a beam diameter of 2 mm) using a 3-axis handling system in a layer by layer fashion to on Ti-6Al-4V substrate to develop a coupon with a dimension of 10 mm x 10 mm x 5 mm using an applied power of 500 W, scan speed of 300 mm/min and powder feed rate of 2.2 g//min and 10 wt.%TiC addition. Addition of TiC leads to formation of defect free microstructures under varied parameters, except a few processing conditions. There is formation of complex carbides (Ti2AlC, Ti3AlC2 and Ti2AlC) in addition to TiC phase in the microstructure of duplex 2+ phase. There is improvement in microhardness due to TiC addition from 490 VHN to 525 VHN. The wear and high temperature oxidation resistance properties have been discussed in detail.

Resume : Growing interest in preparation of thin films and zeolite nanocrystals useful for optical and electronic devices [1], catalytic membranes [2] and chemical sensors [3] has been developed in the recent years. This interest is connected with advantages like chemical and thermal stability together with zeolite nanoparticles’ properties related to their potential size, shape and magnetic selectivity. Despite some different methods exist for zeolite films preparation, the Pulsed Laser Ablation (PLA) is one promising method because of advantages like applicability to any zeolite structure which is important for synthetic materials, films thickness and crystal structure control, among others. The here presented study refers to some synthesized magnetic zeolite target materials treated by PLA under different laser power densities and enviromental conditions like vacuum, air and/or applied magnetic field during laser ablation process. The aim is to investigate the fs pulsed laser effects on zeolite crystal structure and morphology of the resulting deposits and target surfaces in order to find the best set-up conditions giving the required fragmentation and/or preferential orientations of the resulting ablated material. These characteristics are of fundamental importance not only for the study of PLA process on zeolites but also for the evaluation of the resulting zeolite nanocrystals possible applications. For this purpose, both laser-irradiated deposits and targets have been characterized by Scanning Electron Microscopy (SEM) and X-Ray Diffraction analysis (XRD). Morphological results indicated that, depending on zeolite structure and ablation conditions, amorphization, orientation and/or changes in nanoparticle zeolite size took place after the laser irradiation. [1] Herron N. (1995) Zeolites as Hosts for Novel Optical and Electronic Materials. In: Herron N., Corbin D.R. (eds) Inclusion Chemistry with Zeolites: Nanoscale Materials by Design. Topics in Inclusion Science, vol 6. Springer, Dordrecht [2] R. Dragomirova and S. Wohlrab, Zeolite Membranes in Catalysis—From Separate Units to Particle Coatings, Catalysts 2015, 5, 2161-2222. [3] X. Xu, J. Wang, and Y. Long, Zeolite-based Materials for Gas Sensors, Sensors 2006, 6, 1751-1764.

Resume : For a long time antibiotics have been used to kill efficiently bacteria and limit infections proliferation. However, it is well known that pathogens develop resistance to antibiotics over time, which poses a serious threat to human health. The use of metallic and metal oxide nanoparticles as antibacterial agent is been highly studied as alternative. In particular, copper nanoparticles present broad-spectrum bactericidal properties and are prepared from earth-abundant material and inexpensive. In this work Cu foils were ablated in air and Ar atmospheres using a nanosecond Nd:YVO4 laser operating at 532 nm and a picosecond laser Nd:YVO4 operating at 1064 nm to produce and deposit Cu nanoparticles on Ti substrates. The size, composition and crystallinity of the synthesized nanoparticles were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), X-ray diffraction (XRD) and UV-vis spectroscopy. The Cu nanoparticles ion release was also estimated by inductively coupled plasma optical emission spectrometry (ICP-OES), while the antibacterial activity of the samples was tested against Staphylococcus aureus. The obtained coatings consisted of interconnected nanoparticles of copper and copper oxide nanoparticles. The use of Ar contributed to reduce the oxidation degree of the synthesized nanoparticles. The samples of copper and copper oxide nanoparticles deposited on Ti exhibited inhibitory effect on Staphylococcus aureus.

Resume : Ferroelectric thin films have been intensively investigated in the last decades, owing to a combination of dielectric, electric and electromechanical properties with a wide spectrum of applications. It was recently shown that graphene-ferroelectric heterostructures can be successfully used in improving the functionalities of graphene-based transistors/devices. The qualities of the ferroelectric surface and of the growth/transfer process of graphene on it are key issues for obtaining nanoelectronic devices with enhanced properties and functionalities. Lead Zirconate Titanate (PZT) and HfO2 have been chosen as ferroelectric materials. A parametric study regarding the deposition of very thin layers (thicknesses in the nm range) directly on Silicon substrate, with very low roughness and appropriate ferroelectric properties was carried out. Another parametric study is related to properties modification by strain engineering for Y-doped BiFeO3 (Bi0.97Y0.03FeO3) films grown on Nb:SrTiO3(001) substrates. The layers photocatalytic activity was shown to strongly depend of epitaxial strain relaxation due to thickness variation.

Resume : Titanium carbide, TiC, is a non-oxide ceramic exhibiting faced-centred cubic (fcc) crystal structure, a high melting point of around 3 000 °C, and an exceptional hardness of ca. 28 GPa. Electrochemical behaviour, especially vis-à-vis of hydrogen absorption and storage, has already been thoroughly studied, and it has been demonstrated that it changes with the amount of carbon vacancies. In this context, the aim of this study is to compare the electrochemical properties of stoichiometric and substoichiometric titanium carbides, with respect to their substrate type and crystallographic orientation. Thus, thin films are synthetized on various substrates, i.e. MgO (111) and Al2O3 (0001), by pulsed laser deposition (PLD). First, their morphology and structure are investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high resolution X-ray diffraction (HR-XRD). The films are of high quality on all tested substrates, and no delamination is observed. Subnanometric roughness and hetero-epitaxial growth is observed on MgO substrates, following the (111) atomic planes. On c-cut sapphire substrates, TiC films are also preferentially orientated following the (111) plans, yet a phase change seems to be observed, linked to a possible carbon expulsion from the chemical structure. Finally, electrochemical investigations are also performed, and results are corroborated with respect to the structure.

Resume : Although DLC films are already well known and applied widely in industry, they are still constantly being developed and improved through the intensive advancement of vacuum deposition techniques. For example, DLC-silver nanocomposite films, which show favourable friction behavior, biocompatibility and antimicrobial activity, have been produced using different techniques including the thermionic vacuum arc method, PE- and RF PA-CVD. However, for such DLC/Ag composite coatings it would be preferable if the deposition method allowed the amount, size and distribution of the silver particles to be controlled more readily. The aim of our work was to produce DLC/Ag nanocomposite thin films using a simple and convenient pulsed laser deposition technique and define the influence of process parameters on the silver particle formation and film properties. Graphite and silver targets were ablated using a KrF laser in vacuum or nitrogen/argon atmosphere. The structure of the deposited DLC/Ag films was studied by Raman spectroscopy and XRD techniques. The quality of the films, in terms of microcracks, roughness, and silver particle size and distribution, was evaluated by SEM, STEM and AFM methods. The friction behaviour was also investigated. The results clearly indicate that PLD is well-suited to obtain a uniform distribution of silver particles, the size of which can be controlled by the type of assisted gas used during the deposition process.

Resume : The use of different 3D printing technologies for pharmaceutical manufacturing provides new opportunities for personalized medicine and on-demand tailored drug products, such as implants and other dosage forms. In this work we present our recent achievements in developing a viable manufacturing process for printed personalized dosage forms onto thin films. Laser Induced Forward Transfer (LIFT) printing technology has been successfully applied by means of a 355 nanosecond laser to deposit active substances starting from solutions in a wide range of viscosities. The main advantage of LIFT printing lies in the preparation of thin films as dosage forms, each with different designs, multiple actives and sizes. In the context of investigating the effectiveness of the LIFT printing, a Mass Spectrometry (MS)-based analytical technique was developed and applied for the study of paclitaxel printed with LIFT on thin potato starch and glass substrates. The active pharmaceutical ingredient (API) quantification of the LIFT-printed dosage forms was confirmed using a High-Performance Liquid Chromatography tandem Mass Spectrometry (HPLC-MS/MS) analysis. The obtained thin films were characterized regarding their recovery, disintegration time and homogeneity. The final aim will be to develop slow release skin patches containing paclitaxel which will be applied transdermally.

Resume : Printing techniques applied to biology have begun to develop since the 2000s and undergo a high development. Based on interdisciplinary approaches they use a combination of cells, chemistry, engineering and sophisticated protocols for several applications from tissue engineering or organ creation to regenerative medicine and new drug discovery. We took advantage of our experience on the laser-induced forward transfer (LIFT) technique to print bioinks containing stem cells. This method uses a short laser pulse to transfer tiny amounts of material from a thin film donor to a receptor substrate. Under appropriate conditions, the pulse induces a jet formation, propagating perpendicularly from the donor substrate. The targeted material is then deposited as a droplet on the collector. We present the LIFT process optimization allowing to master the bioink deposition in order to create reliable ordered matrices of bioink micro-droplets containing stem cells with a high spatial resolution. The study of jet dynamics using real-time visualizations was carried out and highlighted the need to control both the environmental conditions of printing and the bioinks rheology. By changing the cell concentration in the film and the laser pulse energy we control the droplet size and the number of cells per droplet (from tens of cells down to single cell). This bioprinting process allows to print several kinds of cells on the same substrate which opens new perspectives for tissue engineering.

Resume : Real-time gas sensing technologies with minimum human intervention and monitoring are becoming a requisite in many industrial activities. However, these technologies rely heavily on the low-power consumption capabilities of the gas sensor and its auxiliary circuitry as well as on the effective mitigation of the cross-sensitivity of the materials interacting with analytes. Thin films based gas sensors and their arrays are known to be miniaturization-friendly and less demanding in terms of power consumption. This report offers insights on how to fabricate very sensitive miniaturized conductometric gas sensing structures with designated use as CH4 detectors. For this purpose, thin films of SnO2 mixed with ZnO, in various weight ratios, were grown by pulsed laser deposition on glass, alumina and oxidized silicon substrates, at various pressures (10Pa to 50Pa), in O2 atmosphere. The structures were comprehensively tested in a designated controlled environment, at different concentrations of CH4, in dry and humid synthetic air, respectively and were found to be highly responsive even to concentrations as low as 1ppm of analyte. Satisfying performances, not only in terms of detection limit but also in terms of response and recovery times were obtained even for operating temperatures of 25⁰C.

Resume : Polyaniline (PANi) is an attractive candidate for organic and polymer electronics because of its environmental stability, controllable electrical conductivity and interesting redox properties, offering thus great opportunities for applications in nanoelectronic devices like sensors. The existing methods of obtaining controlled PANi thin films are challenging and request special physical and chemical treatments, both on the substrate surface and for the polymer itself. In this work, matrix assisted pulsed lased evaporation (MAPLE) technique was applied for obtaining the PANi films. In this context, the MAPLE target consisting of aniline dissolved in a solvent is frozen in liquid nitrogen and afterwards is evaporated using a ArF* laser (λ = 193 nm). The influence of the solvent type and of the laser parameters (wavelengths or fluence) on the PANi properties has been also investigated. Next, these films were characterized using X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM), respectively. Furthermore, the obtained PANi film was used as a sensing element within the fabrication of a low-cost conductometric ammonia gas sensor. The detection of ammonia gas has been carried out both, in dry synthetic air as well as in controlled humidity conditions, using an in-house built setup for testing electrical gas sensors. The proposed sensor is highly sensitive for concentrations of ammonia gas below 1ppm and exhibits a prompt, strong and reproducible response.

Resume : In this study, Zr-Cu-Ni-Al (Zr53Cu30Ni8Al8) and Zr-Cu-Ag-Al (Zr53Cu30Ag8Al8) bulk metallic glasses (BMGs) with or without Si additions were produced and laser welded. To provide rapid welding thermal cycles for the BMG welds, the Nd: YAG laser process with preselected laser parameters was used. After the laser welding process, the microstructure evolution and mechanical properties of the welds were investigated and compared. The results showed that the hardness of the Zr-Cu-Ni-Al or Zr-Cu-Ag-Al BMG alloys increased with the addition of Si. Also, after the laser welding process, although all weld fusion zone (WFZs) in the BMG welds were amorphous (observed by TEM), due to the residual stress caused by the deformation in the WFZs of the BMG welds, higher hardness values were obtained in these zones when compared to those of the BMG parent materials (PMs). For the HAZs in Zr-Cu-Ni-Al BMGs (with or without Si additions) welds, the formation of a Zr/Cu binary crystal phase in these zones became unavoidable, which slightly decreased the hard-ness in these zones. However, the plastic deformation ability of these welds was significantly im-proved after the compression tests. For the Zr-Cu-Ag-Al BMGs (with or without Si additions), no crystalline was found in the heat affected zone (HAZs) of the BMG welds, resulting in a similar magnitude of hardness when compared to those of the PMs. However, when compared to the Zr-Cu-Ni-Al BMG (with or without Si additions) welds, the Zr-Cu-Ag-Al BMG welds showed a brittle fracture nature and worse plastic deformation ability after the compression tests.

Resume : Improving and increasing the resolution of laser printed structures has become a need to promote new applications in micro/nanotechnologies. To meet the challenges of reproducibility and versatility, we use the Double-Pulse Laser Induced Forward Transfer (DP-LIFT) technique. A long pulse is first applied to melt the film followed by an ultrashort laser pulse synchronized with proper delay to initiate the material transfer in liquid phase towards the receiver substrate. Thanks to DP-LIFT, liquid melt ejections with controllable jet diameters varied from micrometers to nanometers range are achieved. Interestingly, nanodroplets followed by microjets are seen by shadowgraphic imaging and characterized by scanning electron microscope. Numerical simulation of the temperature evolution for copper film suggests that the observation of nanodroplet relies on jet dynamics. The jet dynamics is heavily modulated by various factors like the shape, diameter and the temperature of the pool. The formation of nanojet is assumed to be the result of a combination of a shockwave and an appropriate pool shape. To validate this hypothesis, studies are made on copper films with different thicknesses and varying femtosecond laser spot sizes on target. The experiment yields direct evidence of formation and break-up of thin nanojets. In order to quantitatively understand the influence of shockwave in this process, the experiment is repeated on Ni-Cu layer.

Resume : Cobalt ferrite thin films with interesting structural and magnetic properties can be obtained by pulsed laser deposition. Their characteristics are influenced by the experimental conditions and thus by the plume dynamics. The analysis of the laser induced plasma can help explain the structural and chemical properties of the deposited nano-structured materials and also optimize the deposition process itself. The aim of this study was to obtain information on the dynamics and properties of the expanding plasma generated by laser irradiation (Nd-YAG: 532nm, 10 ns, 10Hz) of stoichiometric and rare earth doped (CoFe2-xRExO4) cobalt ferrite targets. This was done through space- and time-resolved optical emission spectroscopy using an ICCD camera (PI-MAX3) and a monochromator (Acton SP2750). Both the global dynamics of the plasma and the evolution of individual species were analysed. To have an insight on the contribution of each element, plasma plume analysis of pure cobalt and iron targets were performed in the same conditions as the spinel magnetic material. The laser fluence (5 J/cm2) and gas pressure (10-3Torr) were similar to the ones used for the deposition of thin films, while several of the optical emission spectroscopy experiments were done during the actual deposition process. From the space- and time-evolution of several spectral lines, we determined the velocities of the main plasma plume constituents. The excitation temperature distributions were obtained from the Boltzmann plot, in the assumption of local thermodynamic equilibrium. For a more accurate correlation, the same spectral lines analysed for the pure Fe(/Co) plasma were then considered when studying the cobalt ferrite plume.

Resume : In the nanoscale, surface dominate over bulk effects leading to a different phenomenology in the behavior of materials. This is quite remarkable in the case of metallic nanoparticles raising a great interest on the field of Nanometallurgy. In particular, supersaturated alloy nanoparticles of two metals that present a solubility gap exhibit an enrich phenomenology and, in principle, their Gibbs free energy determines the kind of decomposition that the system shall undergo. Decomposition mechanisms used as a fabrication method provide a straightforward route to homogeneously distribute the decomposed materials and to boost specific properties of the systems. This allows, among others, to nucleate small precipitates at will or to create multilayers of very thin and controlled thickness. The equilibrium phase diagram, predicts the decomposition mechanism that a supersaturated alloy would undergo. However, variations of this phase diagram are expected in the nanoscale and might be brought to light by analyzing the decomposition of nanoparticles. Herein, the decomposition of AuNi alloy nanoparticles of three different compositions at a temperature close to, but below, the solubility gap contradicts the predictions of the equilibrium phase diagram1 and shows that another factors such as the interface energy, the diffusion of the metals, and the strain energy, play an ultimate role to determine the undergoing decomposition mechanisms. (1) J. Mater. Chem. 2012, 22 (12), 5344.

Resume : Wide-gap semiconductors, such as ZnO and GaN, are well known for exhibiting a LASER effect in UV [1], where their resonant frequencies are located. This LASER radiation is commonly interpreted in the context of the recombination of an electron-hole plasma [2]. However, the exact mechanism behind the amplification at room temperature is not yet clearly established, especially the precise wavelength at which amplification takes place was not predictable. In this work, we hypothesize that the mechanism that drives the sharp amplification on the redwing of the recombination spectrum might be the resonant Rayleigh scattering. Firstly, we present here an ab-initio calculation of the optical gain for these two materials, including renormalization of the gap and filling of the bands. This allows to find the carrier density at laser threshold and set the corresponding resonant frequency. Then, we compare the synthetic spectrum resulting from our computation to those obtained experimentally. We show that the experimental amplification fits with high accuracy the Lorentzian shape of the Rayleigh scattering spectrum. Moreover, the shrinkage of the band-gap explains the red-shifting of the LASER peaks, whereas the maxima of the optical gain are blue-shifted. Furthermore, we demonstrated that the FWHM of the LASER peaks, for GaN and ZnO, are given by the damping coefficient of the resonance of the Drude-Lorentz model. [1] H. Zhu et al, J. Phys. Appl. Phys. 50 (2017) 045107. [2] M.A.M. Versteegh et al, Phys. Rev. Lett. 108 (2012) 157402-1.

Resume : The growing interest to SiC nanostructures is based on their exclusive properties that make the SiC material well-suited for uses in heterogeneous catalysis, high power, high temperature electronic devices as well as in biomedicine. In this report the capabilities of laser assisted techniques based on laser ablation and laser induced modification processes for preparation of SiC nanoparticles (NPs) are evaluated. The binary SiC NPs were prepared by ns laser irradiation of the mixture of preliminarily prepared Si and C colloids in ethanol taken in the stoichiometric proportion. The unfocused beam of the second harmonic of Nd:YAG laser (532 nm) with pulse duration of 10 ns, repetition rate 10 Hz and fluences in the range of 230-400 mJ/cm2 was used for laser irradiation. The preparation of SiC compounds was confirmed by the results of the characterization of synthesized particles by the methods of TEM, HRTEM, electron diffraction and XPS. As could be concluded from the TEM and HRTEM images, non-spherical polycrystalline nanoparticles with the mean size about 10 nm were formed in result of co-melting of the initial Si and C NPs. The results of the electron diffraction showed the formation of SiC nanocrystals with a hexagonal internal structure. The synthesized SiC nanocrystals exhibited photoluminescence with a quantum yield of approximately 10% in the visible spectral region that makes them attractive for biomedical applications.

Resume : Pyrolytic nanocarbons (NCs) have been established as materials of choice for catalyst supports and microporous layers in proton-exchange membrane fuel cells (PEM FCs), with R&D efforts focusing on improving yield-to-cost ratios in order to drive down overall manufacturing costs. A critical factor in cost minimization is the amount of noble metal catalyst (traditionally platinum) employed for accelerating the otherwise sluggish ORR and HOR reactions at the FC electrodes. Current successful strategies dictate doping the catalyst supports with co-catalytic trace elements. In our work, we initially target improving on cost-effectiveness by applying laser pyrolytic methods for the synthesis of core-shell NCs of controlled size distribution and morphology. On a second level, we enrich the starting fuel and sensitizer gas mixture (acetylene and ethylene) subjected to the high-power laser irradiation with added diborane and ammonia. The end result is pyrolytic core-shell NCs co-doped with boron and nitrogen co-catalysts, which are further seeded with platinum nanoparticles to serve as catalyst supports for PEM FCs.

Resume : The limitation in the charge carrier injection and transport induced by the reduced diffusion length of exciton and reduced interfacial contact area between donor and acceptor in the classical bi-layer organic heterostructure can be overpassed using as active layer blends of donor and acceptor materials. This paper presents some studies of the organic heterostructures Al/donor:acceptor/ITO realised with mixed layers composed from poly(arylenevinylene)s containing carbazole units substituted at 2,7- and 3,6-positions as p type conduction donor and two different n type conduction acceptors: [6,6]-phenyl C61 butyric acid butyl ester or perylene tetracarboxidiimide, blended in 1:2 weight ratio. The mixed layer was deposited by Matrix assisted pulsed laser evaporation (MAPLE) using a Coherent ComplexPro 205 laser with =248 nm in the following experimental conditions: dichlorobenzene as solvent, fluence 250 mJ/cm2 and number of pulses=20000-30000. The properties of these mixed layers deposited on flat Al will be compared with those of the same mixed layers deposited by the same method on patterned Al obtained by the deposition of Al film on the 2D periodic structures with cylindrical shape realized by UV-Nanoimprint Lithography. The mixed layers have been characterized by spectroscopic (UV-VIS, PL) and microscopic (AFM, SEM) methods and the effect of the type of acceptor and nanopatterning on the optical and electrical properties of the heterostructure has been investigated.

Resume : In the current work, the effect of laser shock peening on chromium (Cr) based electrochemical coatings consisting of 3 mol% yttria stabilized zirconia nanoparticles (YSZ) and carbon nanotubes (CNT) as reinforcements i.e. Cr-YSZ, Cr-CNT and hybrid coating Cr-YSZ-CNT is studied. Coatings were deposited from eco-friendly trivalent Cr solution on steel substrate as a suitable strategy to further enhance mechanical and tribological properties of protective coatings. Cr exhibited an increased hardness after laser peening from ∼8 GPa to ∼9.4 GPa, whereas, maximum hardness value upto ~26 GPa was obtained for Cr-YSZ-CNT hybrid coating system. Enhanced hardness might be accredited to high compressive residual stresses ranging from 634 to 1757 MPa, induced as a result of laser peening. Minimum wear rate of ∼1.8×10−5 mm3/Nm by fretting wear test is recorded in the Cr matrix of laser peened hybrid coating, and a maximum dislocation density of ∼3.0×1016 m−2 was observed which accrue on synergistic reinforcement with YSZ and CNT. An overall improvement in mechanical and tribological properties indicated by low wear constant of the order ~10−6 was achieved after laser shock peening. Addition of YSZ strengthens the Cr matrix, whereas, multi-functionality of CNT provides lubrication along with matrix strengthening as well as bridging effect to crack propagation. Therefore, synergistic role of YSZ and CNT in Cr matrix combined with the laser peening treatment lead to superior properties of coating (Cr-YSZ-CNT) capable enough to limit the problems of wear and erosion in various industrial applications such as aerospace, gar turbines, automotive etc. Keywords: Electro-deposition, Cr coating, Yttria stabilized zirconia (YSZ), carbon nano-tube (CNT), Laser peening, Fretting

Resume : Lithium-sulfur (Li-S) battery is a promising next-generation rechargeable battery with high energy density. Given the outstanding capacities of sulfur (1675 mAh g−1) and lithium metal (3861 mAh g−1), Li-S battery theoretically delivers an ultra-high energy density of 2567 Wh kg−1. However, this energy density cannot be realized due to the shuttling of polysulfide intermediates between the cathode and anode, which causes serious degradation to the cycling stability of a Li-S battery. In this work, a facile laser scribing method is utilized to synthesize a three-dimensional porous graphene interlayer. Besides simplicity and scalability, the synthesis of LSG is conducted at ambient conditions and involves no toxic solvents, which makes this process very attractive for Li-S battery applications. The hierarchical porosity of the free-standing LSG prevents the shuttling of the polysulfide intermediates. Therefore, Li-S battery with LSG interlayer exhibits a high specific capacity of 1160 mAh g-1 at 0.25C with an excellent capacity retention of 80.4%. This is one of the best reported values for Li-S batteries.

Resume : In this work, complex composite coatings based on biodegradable PEG-PCL copolymer and the two bioactive factors, Lf and HA were created via a laser evaporation technique. Scanning Electron Microscopy, EDAX, contact angle and surface energy of the analyzed coatings were correlated to biological response on both short and longer term (72h, respectively 28 days). Human MSC were cultured on the developed coatings and viability, proliferation and morphology were evaluated. All surfaces were shown not to exhibit toxicity, as confirmed by LIVE/DEAD assay. Lf-HA composite exhibited an increase in osteogenic differentiation of hMSC cells, results supported by ALP and mineralization assays. This is the first report about biodegradable composite layers directing osteogenic differentiation from hMSCs and the results indicated that the biodegradable layers have great potential for application in bone regeneration.

Resume : High-temperature thermal treatment is a fundamental method to enhance the crystallinity or to recover its intrinsic properties of nanomaterials. However, the indirect and time-consuming conventional heating methods have hindered high-quality material production with thermally weak inclusions or its applicability due to limited treatment temperatures of such as transparent or flexible substrates. Here, it is introduced the microwave ‘induction’ heating as a selective and fast heating method for conductive thin film. In different with the conventional microwave dielectric heating for electrically polarized molecules, the microwave induction heating has a mechanism that strong current induced by an oscillating magnetic field in giga-hertz frequency generates ohmic heat in conduction thin film. A 20nm-thick silver thin film sputtered on a 5mm-thick glass substrate for low thermal emissivity coating has been selectively heated more than 550oC in 200ms without thermal damage by the microwave induction heating, while the temperature of the glass substrate is maintained around room temperature. The surface resistance of the silver thin film is reduced to near 30% due to crystallinity enhancement, in results, reflectance in the IR region and transmittance in the VIS region are increased.

Resume : Lithium-ion batteries are widely used for widespread applications ranging from portable devices to electric vehicles. However, for developing a high-performance lithium-ion battery further improvements are necessary in term of both electrical performances and safety. In order to accomplish these issues, the design of new composite separators is recommended. The introduction of ceramic nanoparticles, such as alumina, titania, silica or ceria nanoparticles, is expected to impart high thermal stability, good wettability and ion conductivity to the separator. Here ceramic nanoparticles were produced by pulsed laser ablation in liquid, a powerful method for metal oxides nanoparticles (MONPs) synthesis. The effects of pulse duration and wavelengths on composition and size distribution of the nanoparticles were investigated. These particles were thereafter employed to fabricate MONPs/ poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HPF) as separators in batteries by electrospinning technique, a simple and straightforward system to prepare nano or microfiber membranes characterized by high porosity and surface area. According to our results, these MONPs/PVDF-HPF composite membranes exhibit superior thermal stability (in term of thermal shrinkage), electrolyte-philicity, electrolyte uptake and retention.

Resume : UV nanosecond laser annealing (UVNLA) is a very attractive alternative to conventional furnace methods. Thanks to the low absorption depth and the extremely fast heating, UVNLA is a key technology when very low thermal budgets are mandatory. Most UVNLA processes are based on liquid phase recrystallization. In this paper, we investigate UVNLA solid phase recrystallization with an overall thermal budget compatible with 3D-sequential integration. We started from 22 nm thick SOI substrates. Dopants were introduced by ion implantation with conditions leading to a partial amorphization of the silicon layer. Then, we investigated laser annealing conditions with multiple irradiations at the same location using energy densities lower than the melting threshold. Those experiments were performed in a SCREEN LT3100 platform (XeCl 308nm, 100-200ns range). With this sub-melt approach, we observe a progressive solid phase recrystalliza-tion of the amorphous Si layer from the bottom crystalline seed, resulting in a total crystal recovery. Moreover, from sheet resistance measurements, we showed that the resistivity obtained by this process was lower than the ones obtained with melt conditions or high temperature reference process. Dopant activation was therefore most likely higher. We also confirmed by AFM that the Si surface remained very smooth. We thus demonstrated that solid phase recrystallization induced by UVNLA was fully compatible with very low thermal budget CMOS integration

Resume : This study presents results for nanosecond laser ablation of composite thin films immersed in liquids. Composite films are obtained using two different approaches. The first approach involves the subsequent deposition of thin layers of different materials. In the second, a classical on-axis pulsed laser deposition technology is used, where the target consists of two sectors with different composition. Using these approaches, multicomponent films containing ZnO, TiO, Ag, Au, Pd, and Pt are deposited on a substrate. The as-prepared multicomponent samples are then immersed in liquid media and irradiated by nanosecond laser pulses. This results in production of colloids composed by multicomponent nanoparticles. The optical properties of the colloids were evaluated by optical transmittance measurements in the UV– VIS spectral range. Transmission electron microscopy was used to visualize the nanostructures formed in the solution as well as to evaluate of their size distribution. On the basis of selected area electron diffraction, the phase composition of the samples was determined.

Resume : Two-dimensional (2D) materials have attracted significant attention during the last decade owing to their unique optoelectronic properties, which find use in numerous applications including touch sensors, displays and emitters. Current techniques do allow transfer of 2D materials from the growth substrates to a substrate of interest, i.e. for device fabrication, with a high degree of precision and resolution. The large number of steps involved however, (polymer coating, etching of metal support foils, washing steps, post-patterning) results in costly and time-consuming processes that limit their scalability and ease of use. In this work, we report our latest results on the laser transfer of graphene on rigid and flexible substrates using the Laser-Induced Backward Transfer (LIBT) technique, by employing both fs and ns lasers. Using LIBT, single step and micron-scale precise transfer of graphene and MoS2 has been achieved without any post-processing. Additionally, we have employed LIBT for the intact transfer of pixels comprising thin and ultra-thin Au films on polymer substrates, highlighting the potential application of this digital process for 2D/ thin metal interfaces. The transferred structures are fully characterized using Raman spectroscopy, SEM and AFM. These results hold great promise in minimizing the number of transfer steps for 2D and ultra-thin metallic materials, enabling novel device fabrication in a rapid and cost-effective way, with micron-scale precision.

Resume : Polyaniline (PANI) and/or poly(ortho-anisidine) (Poly(o-ANIS)) intercalated in organo-modified clay (OMt) are composites with an extended π-conjugated backbone, combining the organic semiconductor properties and the characteristics of the inorganic compound. In this study, the nanocomposites have been prepared in thin film form by matrix-assisted pulsed laser evaporation (MAPLE). The targets were prepared from polymers and/or nanocomposites synthesized by oxidative chemical polymerization, immersed in DMSO and frozen in LN2. Optical, structural and electrical properties of the obtained thin films are inferred from conventional spectroscopies (UV-Vis and FTIR), X-Ray diffraction, Scanning Electron Microscopy, Atomic Force Microscopy and current-voltage measurements. The results are discussed with respect to the ratio between PANI / Poly(o-ANIS) intercalated in OMt and also with the films of pristine polymers. All authors acknowledge Romanian Ministry of Education and Research in the framework of PN-III-P1-1.2-PCCDI-2017-0062 (no. 58PCCDI/2018), Core Program PN19-03 (no. 21N/08.02.2019) and PFE-CDI-339 (no. 12PFE/2018). A.K. acknowledges Algerian Ministry of Higher Education and Scientific Research for the received mobility research grant (no. 304/PNE/2018-2019) in the frame of Algerian Programme National Exceptionnel (PNE).

Resume : Dewetting is a spontaneous phenomenon that refers to the decomposition of a film into droplets or nanoparticles on substrate. Laser dewetting has proven effective in producing not only monometallic nanoparicle arrays but also bimetallic alloy nanoparticles with tunable surface plasmon resonances. However, the particles produced via laser irradiation typically exhibit a wide size distribution, and the average particle size is determined by the initial film thickness. In this study, we show that if metal thin films are thermally annealed prior to laser dewetting, nanoparticles with a much narrower size distribution can be produced. This is attributed to a morphological change in the film occuring as a result of heat treatment. Experimental results obtained using a pulsed Nd :YAG laser for Ag thin films are presented and discussed.

Resume : Ultrafast laser processing can be accompanied by significant emission of unwanted X-ray radiation. Machining at laser peak intensities above 10^13 W/cm^2 and at high repetition rates in the multi 100 kHz range has a risk of exceeding the statutory X-ray exposure limits [1]. Therefore, radiation protection in ultrashort laser material processing became a new and industrially relevant focus of interest. Additionally, the need for a safe operation of the laser itself must be considered. Utilizing steel and aluminum as shielding materials, adequate material thicknesses for reliable X-ray protection were calculated using measured X-ray spectra for laser treatment of tungsten with 925 fs pulse duration at a center wavelength of 1030 nm, a repetition rate of 400 kHz, and a peak intensity of 2.6×10^14 W/cm^2. Here, the relevant X-ray emission is limited to photon energies below 30 keV. [1] H. Legall et al., Applied Physics A 124 (2018) 407.

Resume : Bacterial biofilm formation poses high risks in many medical and industrial applications. Hence, various strategies are currently developed, tested and improved to realize anti-bacterial surface properties through additional surface functionalization steps. In this study, contact-less and aseptic large-area femtosecond laser scan processing is employed to generate different surface structures in the nanometer- to micrometer-scale on technical materials, i.e. titanium-alloy, steel, and polymer. The processed surfaces were characterized by optical and scanning electron microscopy and subjected to bacterial colonization studies with Escherichia coli and Staphylococcus aureus as test strains. For each material, the results of the fs-laser treated surfaces are compared to that obtained on polished (non-irradiated) surfaces as a reference. In all cases, a remarkably different adhesion behavior of the two types of bacteria is found, suggesting an influence of their geometrical size and shape.

Resume : Amorphous materials are potential material for wide application because of their unique mechanical, physical, and chemical properties. However, its industrial application is not widespread because of limited size and shape. It can be concluded that the production of this type of Fe-based material in the form of direct metal deposition coatings can be an interesting technological achievement. The possibilities of generating metastable materials with the use of generative technologies have not been fully investigated yet and phenomena accompanying coating of the consecutive layers of amorphous/ crystalline alloys have not been explained yet. This research aimed to make specimens having the geometry of a plate using the DMD (Direct Metal Deposition) method as well as to investigate the effect of the number of layers on the structure, nanohardness and Young modulus of fabricated elements. In order to measure the size of the discontinuity of the structure and to determine the shape of the revealed defects, metallographic observations were made with the use of the scanning electron microscope Supra 35 by Zeiss and optical microscope Axio Observer by Zeiss. Because of the width of the particular additive zone, triboindenter, which enabled the measurement in the scope of between ten to twenty micrometres, was used to examine nanohardness and reduced Young module. Acknowledgements This publication and conference participation was financed by the Ministry of Science and Higher Education of Poland as the statutory financial grant of the Faculty of Mechanical Engineering SUT and Rector's Grant in the field of research and development, SUT, no.: 10/010/RGJ19/0272.

Resume : TiO2 is most extensively studied material for its wide applications in sensors, pigments and photocatalysis. When nanometer particles of TiO2 are used, the catalytic activity is expected to be enhanced due to not only the increase of surface area but also the change of surface property such as defects. Herein, we report on the titania doping with vanadium (V+5) and tungsten (W+6) as strategy to reduce the band gap energy of the semiconductor and to decrease in electron-hole recombination rate. Both vanadium and tungsten can substitute the titanium (Ti+4) ion in the titania lattice because of similar radii of the involved cations. Optical, morphological and structural properties of the samples obtained by laser pyrolysis technique, have been revealed by UV-Vis spectroscopy, infrared spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution electron microscopy techniques. The phase composition of the nanoparticle system contains a mixture of anatase and rutile, with a preponderance of the anatase phase (90%) and with mean particle size of about 28 nm. The increase of dopant concentration on the essential structural properties of V/W-TiO2 nanopowders has been determined to be a decrease of the TiO2-anatase phase ratio and of the particle mean diameter value (to about 20nm). The UV-Vis diffuse reflectance spectra showed an absorption shift in V/W-doped TiO2 nanoparticles to longer wavelengths, thus demonstrating an enhancement of the absorption in the visible spectrum.

Resume : We present results on three dimensional (3D) photonic effects in different optically transparent media like flexible PDMS polymer and noble metal enriched borosilicate glass induced by direct laser processing. Short and ultrashort laser pulses generated in the UV-ViS-NIR spectrum are used for direct laser patterning or ablation in local surface or volume area without limit of the planar structures. The special periodicity of the pattern's structure and the optical waveguide arrays formation, and also the tuning of the plasmon-resonance of the nobel metals doped, are explored by varying specific laser parameters and set-up arrangements. The elasticity of PDMS allows tunable control of the structures’ parameters and hence of the photonic effects induced. Photonic (optical and plasmonic) effects in the borosilicate glasses arised after further thermal annealing and/or additional irradiation with laser light. The methods employed enable easy controllable fabrication approach of photonic elements spanning from skin or implantable wearables for healthcare monitoring to implantable neural interface devices as well as the chip-scaled optical interconnects. Different techniques (UV-Vis spectroscopy, x-ray photoelectron spectroscopy, optical and scanning electron microscopy) are used for studying and comparing the optical, compositional and structural properties of both areas - pristine and laser treated ones.

Resume : The first originality of the experiments we carried out consists of the use of a laser beam as a double agent: simultaneously as activation agent inducing the isomerization reaction of the PA, and for the Raman diffusion. The laser beam power P(λ) is equivalent to the temperature T of isotherm i of isomerization reaction. The second originality consists of use of multichannel spectroscopy which enables the simultaneous observation of both reactants (PAcis) and product (PAtrans) in the same time, since PAcis absorption band and PAtrans absorption band are clearly shifted on a band of 512 diodes Then we have a double simultaneity (i) In one hand the heating and the diffusion of the laser beam, (ii) On the other hand the steady measurement of the concentrations. We elaborate a numerical model reproducing the Raman experiment within 5 % error. The rate constants, activation energy values, Arrhenius factors and linear regression coefficients are obtain with a small error. The kinetic results obtained, such as reaction orders values obtained, varying from 1/2 to 2/3, showed clearly that, the isomerization reaction of undoped P.A. remains a complex process. The reaction order of 2/3 seems to be the most appropriate value in this case, since it refers to a solid state reaction propagation, where the reaction rate is controlled by a three dimensional development of active centers, in agreement with Sestak and Berggren theory.

Resume : This work presents a numerical resolution of heat distribution equation of pulsed laser beam impact on a sample of oriented polyacetylene characterized by multichannal Raman spectroscopy. The method is based on finite elements theory which allowed the determination of: (i) The temperature of laser impact zone , (ii) The propagation zone of isomerization of a polyacetylene sample. A computer program was been developed for this purpose. Key Words: Multichannal Raman spectroscopy, Oriented Polyacetylene, numerical resolution, finite elements, isomerization

Resume : We report on the development of novel coatings with improved composition and structure that enhance curative properties of Ti implants. Titanium implants functionalized with Se and Sr doped HA/β-TCP coatings (HA/β-TCP:Se/Sr) were achieved by combinatorial pulsed laser deposition (c-PLD) technique in order to identify the optimum elemental composition with respect to their biological features. FTIR evaluation of HA/β-TCP:Se/Sr samples offered information’s about the functional groups and covalent bonding and revealed the stoichiometric transfer. The elemental composition of the as-deposited coatings was determined from EDS and XPS measurements and pointed out the Se and Sr dopants content. The morphological features and the crystalline state of the as-deposited coatings was evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses, respectively. The cytotoxicity, viability and proliferation of HA/β-TCP:Se/Sr were evaluated in order to establish the optimal concentration of Se and Sr. The aim of this study was to fabricate metallic implantable devices covered with thin films of HA/β-TCP:Se/Sr composite designed for bone tissue therapy that stimulate the osseointegration.

Resume : Titanium Nitride (TiN) has emerged as a promising alternative plasmonic material that may outperform the traditional plasmonic metals, such as Au and Ag in terms of durability to high temperatures and/or to the high electric fields of concentrated light present in most realistic plasmonic applications. TiN is a well-known conductor of high mobility, widely used in the mainstream microelectronics industry, and it owes its electronic conductivity to the partially filled valenced orbitals that are not completely hybridized with the N-2p electrons and presents high optical response similar to that of Au, hence its golden optical appearance, when in stoichiometric form; non-stoichiometric TiNx>1 films are also reported and are predicted to exhibit Localized Surface Plasmon Resonance (LSPR) in red and Near-Infrared (NIR) ranges. TiN is usually grown in thin film form by sputter deposition, its bottom-up nanostructuring was not successful so far, and the formation of colloidal TiN is exceptionally rare, both due to the refractory character of TiN, which is a major obstacle for its wide range implementation. The scope of this work is the synthesis of colloidal TiN and TiNx nanoparticles with tunable LSPR from the visible to the NIR spectral ranges, thus covering the entire biological window, a property that can find use in many different biomedical applications, such as the healing of tumors by plasmonic hyperthermia. The TiN and TiNx nanoparticles (NPs) were fabricated by the following two steps process: a) picosecond laser ablation of thick TiN and TiNx thick films in liquid media for the synthesis of the Colloidal TiN NPs and b) nanosecond Laser irradiation of the Colloidal TIN NPs for the downsize the TiN NPs in the liquid media and the tuning of the LSPR. For this purpose, TiN films grown by UHV Reactive Magnetron Sputtering. The crystallinity, conductivity and stoichiometry of the films can substantially vary by varying the bias voltage applied to the substrate (Vb=0 to -120 V) and the substrate temperature (T=RT to 400 oC). The chemistry, crystallinity, optical properties, and the point defects of the target materials were evaluated by X-Ray Diffraction, X-Ray Photoelectron Spectroscopy, Spectroscopic Ellipsometry and Raman spectroscopy, respectively. Then, the major laser ablation parameters were investigated, in particular the wavelength (532, 355, 266 nm), fluence (1-30 mJ/cm2), and the number of pulses. The optical properties, the size, and the structure/defects of the produced TiN nanoparticles were assessed by optical transmittance spectroscopy, atomic force microscopy, and Raman spectroscopy, respectively.

Resume : Laser Surface Cladding is a process of development of surface layer, by laser surface melting of the coating in the form of wire or powder and delivering the molten material on the surface of a substrate with minimum dilution at the interface. The process may be applied for the development of alloys, metal matrix composite and intermetallic covered surface on metallic substrate. In the present contribution, a detailed study on the development of compositionally graded surface by laser surface cladding has been presented. The detailed study would include development of compositionally graded metal matrix composite on mild steel substrate, and SiC dispersed aluminium composite on aluminium for wear resistance application. Laser surface processing has been carried out using continuous wave CO2 laser, or Diode laser. The effect of process variables on the microstructures, mechanical properties, and electrochemical property has been studied. Finally, the mechanism of wear and corrosion resistance has been established. Laser surface cladding under optimum process parameters leads to development of a defect free clad zone with a minimum heat affected zone. Laser power density and scan speed play important role in determining the thickness of the clad zone, microstructure and microhardness. The detailed structure-property-process parameters correlation for the laser surface cladding is established.

Resume : Many living beings in nature, including the lotus leaf, rice leaf, butterfly wing and water-strider legs are the inspiration for many innovations and continue to serve as an invaluable resource to solve technical challenges. Such surfaces possess several unique beneficial properties, such as extreme water repellency, self-healing, self-cleaning, anti-bacterial, anti-corrosion, enhanced heat transfer, drag reduction and improved corrosion resistance. Recently, superhydrophobic surfaces, for which water contact angle is higher than 150° and sliding angle less than 10°, have received attention due to the many potential applications ranging from biological to industrial processes and usable/applicable properties, even in daily life. In this paper, an innovative, flexible and low-cost experimental set-up for producing superhydrophobic metal surfaces that are modeled by nanosecond laser ablation is shown. One of the goals of this patterned superhydrophobic metallic surfaces is to obtain a device to be used in samples surface preparation of materials such as: polymeric materials; out of these polydimethylsiloxane-PDMS, polyethylene terephthalate-PET, synthetic latex polymers, polyvinyl chloride-PVC materials are considered. The polymeric structures have the same properties as those of the metal pattern used to generate them and are employed in a large number of applications in: biology, food industry, marine industry and textile industry.

Resume : In this study, cerium-doped yttrium aluminum garnet (YAG:Ce) blended with SiO2 to improve the sintering density was prepared by two different processes, one is solid state reaction (SSR) and another is laser sintering (LS). By using instruments of x-ray diffractometer (XRD), scanning electron microscope (SEM) and x-ray photoelectron spectrometer (XPS), the crystal structure, surface morphology, and dopant valence state of the above SSR and LS YAG:Ce ceramics were compared, respectively. XRD patterns presented both processes could transform precursors successfully into a YAG phase with no detectable impurity phase. SEM images revealed the surface morphologies of SSR and LS were crystallites with xylem-shaped structures and coral-shaped structures, respectively. XPS spectra revealed that the SSR process had one additional peak and high peak intensities of Ce4+ as compared to LS. The ratios of Ce3+ to Ce4+ was 8:9 and 5:4 in SSR and LS, respectively. Based on the above XPS spectra, it is believed that a sharp temperature increase could deplete the surrounding oxygen as laser beams scanned on precursors, resulting a reduction of valence state of Ce from +4 to +3 in the LS process. Therefore, the better photoluminescence as well as higher fluorescence efficiency in LS process than those in SSR process was mainly caused by their different valence states. The detailed will be present in the conference.

Resume : Silicon carbide (SiC) is a wide-band gap semiconductor, known for its excellent electronic properties and durability. Beyond its typical application in high power transistors, SiC recently received a new boost of research interest from the LED, battery and catalysis community. However, an obstacle in those fields is the common preparation of semiconductor grade SiC starting with the growth of expensive single crystalline wafers, even if actually porous, nanostructured or powdered material is needed. Here, we present first results on a novel approach to tackle this problem: Localized synthesis of SiC by laser-induced carbothermal reduction of silicon oxycarbide (SiOC). We will discuss and share our latest insights of this promising process, e.g. how the underlying multistep reduction reactions within SiOC require careful adjustment of lasing parameters and atmosphere to proceed with appropriate balance, to lead to SiC formation. Apart from the vital Si/C ratio and morphology of the SiOC, which is customized by chemical synthesis, this is discussed with regard to its heat capacity and thermal conductivity, but also thermal onsets of the reactions, effect of dopants, reaction dynamics and kinetics. Finally, first physical characteristics of the laser-derived SiC will be presented. Once the process is understood and thus controllable, it would make a fine technique to simply write SiC semiconductor tracks, create structured layers or particles, just by lasing.

Resume : The surgical intervention on hard tissues has emerged in the last years, therefore researchers, engineers and clinicians seek for efficient alternatives to develop tailored biomaterials. In this study we have developed an innovative thin film containing hydroxyapatite and silver nanoparticles, with good biocompatibility and antimicrobial effect, to be used in hard tissue engineering. Bioactive coatings were obtained by MAPLE (matrix assisted pulsed laser evaporation) and physico-chemically characterized by DRX, DTA-TG, and SEM. Biocompatibility was assessed by fluorescence microscopy and the MTT assay, on human diploid cells, while antimicrobial potential was analyzed in Gram positive and Gram negative opportunistic pathogens. The results revealed that the obtained materials are uniform and well organized, with the an average film thickness of 600nm. The developed nanostructured films presented a good biocompatibility in vitro, allowing for normal development and growth of human cells. On the other hand, the nanostructured thin film inhibited the attachment of microbial cells and also the formation of monospecific biofilms. Good biofilm inhibition was observed in Staphylococcus aureus and Pseudomonas aeruginosa strains, two of the most important opportunistic pathogens involved in device-associated infections and bone regeneration failure. The developed materials proved a good compatibility and an increased ability to limit microbial attachment and biofilm formation.

Resume : Ternary metal oxides are a promising class of multifunctional materials that can efficiently fulfill the major energy and environmental needs. Nickel molybdate (NiMoO4) particularly, presents excellent properties in addition to its non-toxicity, cost-efficiency and chemical stability, that render it suitable for a broad domain of applications. The present study focusses on NiMoO4 particles, synthesised by co-precipitation method in aqueous solution at room temperature. The resulting powder was subsequently characterized by scanning electron microscopy and energy dispersive X-ray spectrometry (SEM/EDS). Besides confirming the expected stoichiometry, the analysis revealed homogeneous distribution of polydisperse non-aggregated microsheets-like NiMoO4, crystallized in α-form, as shown by X-ray diffraction (XRD). The main objective of this communication is to test out electrochemical properties of this oxide, and to check their dependence on the substrate nature. For this, NiMoO4 powder is pressed into a 15 mm diametre disc. Thin films are subsequently grown on various substrates, such as kapton/Au sheets, Si (100), and BK7 glass slides, by using a KrF ns-pulsed UV laser. Results are presented and discussed mainly in terms of crystalline phase and crystallites dimensions, and corroborated to thin film roughness and their electrochemical behaviour.

Resume : The work proposed herein investigates the possibility of using clay thin films prepared by laser techniques as absorbents for heavy metals from aqueous solutions. Thin films of lamellar clays were deposited by laser techniques (matrix assisted pulsed laser evaporation (MAPLE), pulsed laser deposition (PLD)). The main property of these materials is the adsorption capability, which is connected to the layer charge density, cationic charge capacity and swelling characteristic. The considered clays were layered double hydroxides and montmorillonite. Aqueous solution of CuSO4 with different concentrations were used for the immersion of the films. Energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) were the techniques employed to assess the copper uptake. Chemical, structural and morphological properties of the films were investigated before and after immersion for the identification of the adsorption mechanism taking place.

Resume : Ultra high precision machining of surfaces require gentle tools for high resolution, low-defect material removal at normal pressure that can be easily computer controlled. However, laser machining techniques still do not fulfill all requirements for such applications. Plasma processes enable high quality etching of various materials but require vacuum conditions. Laser and plasma processing are complementary technologies where each technology has its inherent advantages and shortcomings. In this presentation, a novel technology will be introduced which combines plasma and laser processing in order to make use of the advantages of both technologies. An ultra-short pulse laser source was used to generate a localized, free-standing micro plasma in a gas at atmospheric pressure by an optical breakdown. In order to modify, etch or deposit material, the plasma is brought in the proximity of a surface to allow the interaction of the species of the micro plasma with the surface. In particular, etching of fused silica and polyimide is discussed. These are reference materials etched by the laser-generated, reactive plasma that contains chemical species such as fluorine, chlorine or oxygen. In the presentation, the impact of selected parameters such as laser pulse energy, temperature, pressure, gas composition or plasma-surface distance on the etching rate and surface characteristics are shown. SEM, AFM, and XPS investigations reveal the achieved surface qualities and remarkable small chemical as well structural modifications.

Resume : The temperature dependence of the luminescence properties is important for understanding the carrier dynamics of optoelectronic devices utilizing an ensemble of quantum dots (QD) such as lasers and solar cells. Photoluminescence (PL) spectroscopy is an effective methodology to investigate luminescence properties. On the temperature dependences of the PL peak energy in GaAs QD, the red-shift from the expected Varshni law around 100 K has been already observed. We recently observed an additional blue-shift in the higher temperature range above 150 K for the GaAs QD samples grown by droplet epitaxy. We have explained this behavior by a steady state rate equation model with presences of the size distribution of the QD as well as the carrier transition from the QD to the coupled excited states (CES). In this study, an excitation light intensity dependences of the PL peak energies were measured for confirming the usefulness of the steady state model. As a result, a reduction of the red-shift and an enhancement of the blue-shift were observed by increasing the excitation light intensity. The former reduction of the red-shift was well explained by supposing the carrier density in the CES increased by the strong excitation in our proposed model. However, the latter enhancement of the blue-shift could not be reproduced yet. This may be explained by an activation of other non-radiative centers due to the population of photo-excited carrier to higher energy states.

Resume : Semiconducting metal oxides are known to undergo changes in their properties electrical, optical, or mechanical in response to an external stimulus. This behavior makes oxide semiconductors highly promising materials for a number of chemical sensor applications and sensing schemes. In that context, new type of sensors based on the laser-induced photoluminescence (PL) emission of nanostructured materials (e.g. ZnO, CoTiO3, NiTiO3) and their capacity regarding their sensing properties will be presented [1,2]. Their sensing behavior has been investigated at different surrounding atmosphere (ethanol, oxygen) and temperature conditions (290-340 K), exploring both weak and strong laser excitation. For the optical characterization and the study of the PL emission the samples were optically pumped with laser sources of proper wavelength and pulse width (Nd:YAG laser, λ=355 nm, τ=8 ns; KrF laser, λ=248 nm, τ = 450 fs). The observed variability of PL indicators such as spectral intensity and width, offers a systematic way to monitor the environmental changes in a reliable manner, opening the path for exploiting oxide materials, as optical sensors even at remote distances or hostile environments. 1. A. Klini, M. Androulidaki, and D. Anglos, “Low Energy Pulsed Laser Excitation in UV Enhances the Gas Sensing Capacity of Photoluminescent ZnO Nanohybrids,” Sensors 19, 5490 (2019). 2. S. Murcia-López, M. Moschogiannaki, V. Binas, T. Andreu, P-Y. Tang, J. Arbiol, J. Jacas, G. Kiriakidis, J.R. Morante, “Insights into the Performance of (CoxNi1-x) Titanates as Photo- and Electro-Catalysts for Sun-Driven Water Oxidation,” ACS Applied Materials & Interfaces 9, 40290-40297 (2017).

Resume : Processes for spatially structuring the functional properties of organic materials involve structuring a deposit like lithography i.e. weak flexibility. Here, we show the creation of luminescence in organic compounds on the scale of a few microns using the special properties of the focused femtosecond laser (1030nm, 250fs, 0.6NA). We thus acquire the possibility in the field of organic photonics to spatially modify physical properties using a particular photochemistry. It is commonly thought that the femtosecond laser, because of its great intensity (power per unit area) can produce in organic materials only ablations. In fact, a delicate control of the parameters makes possible to access local chemical modifications that produce new molecules and therefore new physical properties, here a luminescence in the visible, for example. The material we use here for the demonstration is an amino acid. Some luminescence is created in a limited range of pulse energy and repetition rate. We observe two domains in the plan (pulse energy x repetition rate) where 2 kinds of chromophores are appearing, one with a short lifetime (0.4-0.7ns) and another one with a longer one (1.5-3.5ns). The luminescence spectrum is peaking at 560 nm under 488 nm excitation. The short lifetime chromophore is mainly created at low pulse energy (below 0.4 µJ/pulse for 1MHz) in the full volume of the focus and the large lifetime chromophore is rather appearing on the wall of the modified volume at higher energy.

Resume : ZnO nanowires-based surface-plasmon-polariton (SPP) nanolasers with metal-insulator-semiconductor hierarchical nanostructure have emerged as potential candidates for integrated photonic applications. Herein, we demonstrated a SPP nanolaser consisting of ZnO nanowires coupled with single-crystalline aluminum (Al) film and WO3 insulating interlayer. High-quality ZnO nanowires have been prepared by using vapor phase transport and condensation deposition process via catalyzed growth. Subsequently, as prepared ZnO nanowires were transferred on a single-crystalline Al film grown by molecular beam epitaxy (MBE). Meanwhile, a WO3 dielectric interlayer has been deposited in-between of ZnO nanowires and Al film via e-beam technique for preventing the metallic region dominated optical loss. Such metal-oxide-semiconductor (MOS) structured SPP laser with optimal thickness of WO3 (3.6 nm) insulating layer demonstrates an ultralow threshold laser operation (lasing threshold of 0.79 MWcm-2). This threshold value is nearly 8-times lower as compared to that of previously reported similar ZnO/Al2O3/Al plasmonic lasers. Such suppression in lasing threshold is attributed to WO3 insulating layer mediated strong confinement of the optical field in the subwavelength regime.

Resume : We report on the preparation by Pulse Laser Deposition of DLC (ta-C) films on transparent quartz. Subsequently, minute amount (less than a monolayer) of transition metals (TM = Fe, Co, Ni) is deposited on these ta-C films (TM/ta-C/quartz sample) (1). Finally a thermocatalytic treatment is carried out to transform part or all the ta-C into a thin graphitic layer. Apart from the nature and the dose of metal evaporated, the thickness and the sp3/sp2 ratio, controlled by the PLD parameters (time and laser fluence), and the temperature and the nature of the gas treatment, were the key parameters investigated. The location of the metallic nanoparticles was investigated by XPS while the formation of graphitic domains was investigated by Raman spectroscopy. The choice of the transition metals has been operated as a function of their high reactivity to carbon-carbon bond with transition metals but also to their ability to absorb carbon. The system TM/thin graphitic layer/DLC/quartz exhibits under optimized conditions both high optical transmission and high surface electrical conductance, with figures of merit (conductivity of transparency) higher than ITO. We observed an optimum in the fluence as well as the thickness of the DLC layer. Ref : “Kinetics of graphitization of thin diamond-like carbon (DLC) films catalyzed by transition metal” N. Boubiche, J. El Hamouchi, J. Hulik, M. Abdesslam, C. Speisser, F. Djeffal and F. Le Normand, Diamond and Related Materials, 91 (2019) 190-198.

Resume : Nowadays micro/nano- technologies depend on processing tools able to structure materials in 2D and 3D with utmost precision. Ultrafast lasers can take up ambitious processing challenges where energy localization is critical. A limitation, intrinsic to optical methods, is related to diffraction, restricting irradiation to sizes comparable to the wavelength. However bypassing the diffraction limit is key for a new range of applications in optics and mechanics requiring access to the nanoscale. Possible solutions rely on material evolution in non-equilibrium conditions. Exploiting the nonlinearity of excitation and non-equilibrium, ultrashort laser pulses can show remarkable capacity to localize light on subwavelength scales, building up on collective carrier effects on surfaces and in the bulk. We will discuss here the capability of ultrafast laser to achieve structuring on 100 nm scales. We will show how control of laser interaction by beam spatio-temporal design, notably Gauss and Gauss-Bessel beams with engineered dispersion, can drive physical paths on smallest scales. One relevant application is related to photonics, notably the fabrication of optical devices based on laser-induced 3D refractive index engineering. Discussing the mechanisms of photoinscription we will follow the dynamics of electronic excitation in confinement conditions and point out characteristic times of energy deposition, serving as guidelines for high resolution. We pinpoint their potential to generate photonic systems where hybrid micro/nanoscale features can develop advanced optical functionalities.

Resume : The formation of laser-induced periodic surface structures (LIPSS) in industrially relevant metallic, semiconducting, or ceramic materials usually takes place under atmospheric conditions. Since the laser-induced formation of superficial oxides changes the material’s optical response, this can influence the formation of LIPSS in all materials that are prone to oxidation. Hence, the in-depth understanding of the involved mechanisms becomes essential to exploit in full the capabilities of these structures for specific applications. In this work, we fabricate a new type of low spatial frequency LIPSS (LSFL) on the hard coating material chromium nitride using two different direct-write infrared femtosecond laser systems. Some resulting structures are unexpectedly parallel to the linear laser beam polarization used. Chemical, structural and morphological characterizations are performed on the irradiated samples using Raman spectroscopy, X-ray diffraction, atomic force microscopy and scanning electron microscopy respectively. The findings serve as input to finite-difference time-domain (FDTD) numerical simulations of the intensity distributions in an oxide film covered sample at different positions along the laser beam axis, suggesting that the parallel LSFL are formed at the sub-surface interface between the pristine sample material and a thin covering laser-induced oxide layer made of different graded oxide types.

Resume : The processing of transparent materials by lasers oftentimes involves the use of high power ultraviolet sources or ultrashort pulsed laser in order to take advantage of non-linear absorption mechanisms for surface structuring. Moreover, applications such as decoration, wettability or antibacterial properties necessitate textures with sizes in the micro- or submicrometer range. In the last 10 years Direct Laser Interference Patterning (DLIP) has become increasingly important as a micromachining technique, thereby periodic microstructures can be generated by the coherent superposition of two or more laser beams. In the present work, glass (Soda Lime) has been textured through DLIP employing an ultrashort pulsed (10 ps) green (532 nm) laser source. The glass substrate, completely transparent at the given laser wavelength, could be selectively ablated. With a proper selection of the laser fluence dose, periodic dot-like and line-like structures with spatial periods ranging from 9 µm to 2.3 µm could be realized, employing two- and four-beam interference surface configurations. Highly homogenous structures can be obtained for both configurations, with structure depth of up to 1.2µm. The topography of the structured areas was investigated using optical confocal microscopy. The wettability behaviour of the textured surfaces has been also characterized by contact angle measurements, revealing a super-hydrophilicity for most of the treated samples. Moreover, tribological investigations revealed a decrease in the wear track for comparable measured friction coefficients.

Resume : We study femtosecond laser interactions in various bandgap materials at non-conventional driving wavelengths from the deep-ultraviolet to the mid-infrared part of the spectrum. The range of nonlinear responses accessible by radiation tuning allow to revisit questions as important as the achievable resolution in laser machining technologies. In particular, we establish that the concept of nonlinear resolution is not applicable for femtosecond laser ablation. Independently of the nonlinearity of interaction, we find a systematic one-to-one mapping between femtosecond laser ablation features in dielectrics and beam contours at a strict threshold-intensity. This is because any observable based on threshold-based response (as ablation) simply ruins all potential benefits that could be expected on resolution from the nonlinear confinement of absorption. Accordingly, the use of extreme UV should not be overlooked to reach the nanoscale resolutions routinely achieved in lithography. At the opposite side of the spectrum, ultrashort infrared laser pulses open opportunities to tailor in the three dimensions (3D) some semiconductors inside which breakdown regimes were inaccessible until recent demonstrations. Our first proposed solution uses hyper-focused beams to demonstrate permanent modifications in the bulk of silicon with sub-100-fs. For more practical alternatives, we rely on optimizations in the time domain. We generate and apply ultrafast trains of pulses at the highest achievable repetition-rates (up to THz). This introduces unique multi-timescale control parameters used for improved energy deposition and reliable 3D laser writing deep inside silicon chips.

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

Resume : Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique was used to obtain blended thin films based on poly(N-alkyldiketopyrrolo-pyrrole dithienylthieno[3,2- b ]thiophene) (DPP-DTT) and fullerene C60. DPP-DTT is a low band gap polymer (1.7 eV) featured by a high mobility and stability used in the various fields such as photovoltaic cells, OFETs, etc. MAPLE is usually involved in the preparation of organic semiconductor films taking into account that the chemical structures of the raw materials are not affected by the laser beam and the thickness of the obtained films are controlled during the deposition. Thus, organic layers based on DPP-DTT and C60 in different weight ratios were deposited by MAPLE using chloroform as solvent and a low laser fluence. A throughout characterization of the MAPLE films was made for evidencing the influence of the ratio between the two organic components on their optical and electrical properties. The optical features of the DPP-DTT are identified in the UV-VIS and photoluminescence (PL) spectra of the MAPLE films. The vibration fingerprints of the raw materials were observed in the infrared (IR) spectra of the deposited organic films. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) images revealed the globular morphology characteristic to the films deposited by MAPLE. The current-voltage (I-V) characteristics of the fabricated blended structures recorded in dark and under illumination show that their electrical parameters are strongly related by the DPP-DTT:C60 ratio. The results proved that using MAPLE as deposition technique blended organic thin films based on DPP-DTT and C60 with tuned electrical properties can be prepared, these being further integrated in organic devices for different applications.

Resume : Investigations of new red phosphors are presently extremely abundant area of materials research. Synthesis of Y2O3 nanoparticles with monoclinic structure is still a challenging task. In this work, Eu:Y2O3 nanoparticles were obtained via cw CO2-laser vaporization with subsequent condensation of vapor in a buffer Ar gas flow (0.1 and 0.5 atm) in a vaporization chamber. XRD analysis shows that laser vaporization enables crystallization of Y2O3 in the crystal structure belonging to monoclinic symmetry class (C2/m space group). HRTEM evidences formation of high crystallinity spherical nanoparticles with the particle sizes dm~10 nm (0.1 atm of Ar) and 15 nm (0.5 atm of Ar). PL spectrum in the vicinity of 5D0→7F0 transition demonstrates three peaks consistent with three inequivalent positions of Eu3+ ion in m-Y2O3 lattice. 5D0→7F2 transition dominates in the spectrum, admitting the lack of inversion symmetry at Cs sites occupied by Eu3+. The spectrum is expanded to the red part of spectrum due to intense transitions terminating at higher-lying components of crystal-field-split 7F2 energy level. Obtaining chromaticity coordinates (0.669, 0.331) is possible using red phosphor based on m-Y2O3:Eu3+. Current investigation revealed unique possibility of crystal field shaping of Eu3+ PL spectrum in a polymorph of Y2O3 which will result in high color purity and meets technology needs in a number of wLED applications. This work is financially supported by the RFBR № 19-32-60027.

Resume : Amorphous hydrogenated silicon (a-Si:H) attracts scientific interest for thin-film photovoltaics. Femtosecond laser nanocrystallization can improve such a-Si:H solar cells. For example, degradation of a-Si:H electrical properties under sunlight (Staebler-Wronski effect) can be minimized. Also femtosecond laser modification can lead to formation of laser-induced periodic surface structures (LIPSS) on a-Si:H, which induce optical and electrical anisotropy [1] and can be used in optoelectronic applications. In this work we investigated anisotropy of structural, electrical and photoelectrical properties of a-Si:H films modified by femtosecond laser pulses in raster mode. On the modified surface we observed various LIPSS types formation, with parallel or perpendicular orientation relative to laser polarization. Electrical measurements showed that dark conductivity of modified films increased due to formation of silicon nanocrystals by femtosecond laser pulses. According to Raman spectroscopy nanocrystalline phase volume fraction was up to 30%. Also, anisotropy of dark conductivity and mobility of charge carriers was observed in the a-Si:H films after femtosecond laser irradiation. This can be explained by LIPSS depolarizing effect and non-uniform film crystallization both within raster lines and LIPSS. The work was supported by the Russian Foundation for Basic Research (project 19-32-70026). [1] Shuleiko D. V., Potemkin F. V., Romanov I. A., et al. Laser Phys. Lett. 15:056001 (2018)

Resume : In this work results on laser assisted formation of gold and silver nanoparticles in glass are presented. The sample material is Au/Ag-doped borosilicate glass obtained by conventional melt quenching method. The produced glass samples are irradiated by nanosecond and femtosecond laser pulses with a wide variety of parameters – wavelength, fluence, and applied pulse number. At certain conditions both nanosecond and femtosecond laser radiation induces formation of yellow colored areas in the material. The transmission spectra and TEM analysis indicate formation of Ag nanoparticles in the irradiated zones. After annealing of the samples, the irradiated areas lose their yellow coloration, and express red color whit clear dip in the transmission spectra. This effect is related to decomposition of the initially formed Ag nanoparticles and formation of gold nanoparticles and their optical properties defined by plasmon resonance. The optical properties of the irradiated areas for the both regimes are found to depend on the laser processing parameters. These dependencies, the mechanism of nanoparticle dynamics, and the possibility of formation of composite Au-Ag nanoparticles are discussed. This method can be used in fabrication of 3D nanoparticles systems in transparent materials that can be applied in the design of new optical components as metamaterials and in plasmonics.

Resume : Metal nanostructures and nanocomposites based on metal nanoparticles embedded into dielectric matrices are currently objects of extensive research thanks to its properties. Of the greatest interest of which are phenomena associated with plasmon resonance. Plasmons, which are collective vibrations of electrons, arise when the metal-insulator or semiconductor-insulator interfaces are irradiated by a laser of a certain (resonant) wavelength (frequency). The existence of localized plasmons is due to the resonant excitation of electrons in metal nanoparticles, which manifests itself in resonant absorption and scattering of electromagnetic waves, the formation of strong electric fields near the nanoparticles and related effects. In this paper, we propose a theory of this phenomenon based on the kinetic equation method. The kinetic equation method is used to study the peculiarities of electron interactions with the surface of a spheroidal metal nanoparticle when the electron scattering from the particle surface becomes a dominant effect. The frequency dependencies of the components of the electric conductivity tensor were found, and their dependence on the spheroidal aspect ratio was investigated. We predict the surface plasmon line width in metal nanoparticles with varying the dielectric constant of an embedding medium.

Resume : In our understanding, aluminum alloys exhibit the characteristics of light weight, good formability, good specific strength, good corrosion resistance and recyclability. According to the material nature, aluminum alloys are widely applied in aerospace, construction, automotive, and medical applications. In point of view of the lightweight, the specific strength of traditional aluminum alloys is usually lower than that of titanium alloys. Hence, global researchers have done their efforts to develop advanced aluminum alloys with higher specific strength to further increase the degree of lightweight. Therefore, the Scalmalloy with a higher specific strength than traditional aluminum alloys were developed. The scandium is an extremely effective grain refiner for the aluminum alloy, which causes a significant change in the microstructure and properties of aluminum alloys. However, because it’s strength is higher than that of traditional aluminum alloys, it is more difficult to be shaped up or deformed through traditional processes. In this study, selective laser melting (SLM) process was introduced for sample manufacturing. Meanwhile, since different cooling rate/thermal history from the surface into the melting pool may cause different size/distribution of precipitates during the 3D printing process. This study is aimed at the development the heat treatment parameters of Al-Sc alloy after the 3D printing to unify the size/distribution or the precipitates. Thus, the microstructure analysis (such as TEM, XRD, EBSD, etc.) and tensile tests would be conducted and examined carefully to evaluate the optimized heat treatment parameters.

Resume : In recent years, 3D printing technologies have been applied widely, and lots of medical devices such as implants were fabricated by 3D printing technologies. Due to the needs of customization, the shape of the implants were mostly made in irregular to fit the shape of reconstruct joint/bone. Besides, in order to improve the bone ingrowth into the implants, the porous structure were usually introduced. On the other hand, in terms of mechanical property, the rougher surfaces on the surface of struts would cause stress concentration which would decrease strength, ductility, and fatigue life of porous materials. Moreover, in previous studies, rough surfaces may cause mechanical degradation due to stress concentration effects, and the relationship between surface roughness and strut diameter can affect the work of fracture. According to the shape of porous structure, the design biomedical materials is mostly complicated and the pore size of porous structure is only several hundred micrometers. Therefore, the surface treatments are very hard to be achieved by traditional method such as tool machining. However, the strut of the porous samples fabricated with 3D printing exhibit rough surfaces with some manufacturing imperfections. Hence, global researchers have done lots of efforts on the post treatment of 3D printed samples to improve surface roughness. Among the post process methods, electropolish is much more promising to deal with such irregular porous materials. In this study, titanium alloy (Ti64) which is widely used as biomedical materials was printed by using Selective Laser Melting (SLM) technology. The surface roughness of the printed porous samples was modified by electropolishing. The impact of surface roughness on mechanical properties was examined in terms of work of fracture through compression testing.

Resume : Nowadays, more and more biomedical materials are applied in human body. Among the materials, Ti-6Al-4V are the most common used metal biomaterials due to the outstanding biocompatibility. However, Alzheimer disease may be caused by aluminum ions and carcinoma of gallbladder may be caused by vanadium ions released into human body. Because of that, developing toxic free biomaterials becomes an important issue, hence, Titanium-Tantalum alloy is developed to replace such as Ti-6Al-4V and other materials. Moreover, due to the advantage of porous structure, such as the improvement of bone integration and controllable mechanical properties, more and more porous implants are made by 3D printing technology. In this study, the aim is to prove the biocompatibilities of 3D printed Ti-Ta samples are equal to the parts made by the Ti-6Al-4V powders produced at brand of Renishaw(UK) and Circle(TW) to identify the medical used potential of 3D printed Ti-Ta alloy. To clarify the survival rate of the cells, L929 cells were used and cultured with the medium that soaked metal powders before experiments. After that, survival rate of the cells which were cultured for one day and three days was observed by MTT assay. Furthermore, cells were cultured on the surface of Ti-Ta and Ti-6Al-4V samples which printed by selective laser melting (SLM) technology to analyze adhesion rate.

Resume : Cubic fluorite structures of 20Ni-SDC/8YSZ thin films are deposited on Pulsed laser Deposition (PLD) at 500?C and 600?C, at different number of pulses (90.000 pulses for 8YSZ and 36.000 pulses for 20 Ni-SDC) like anode for µSofc and reference electrode for potentiometric oxygen sensor on different substrates (Si(100) and Ti). Dense 8YSZ thin film is used like substrate for Ni-YSZ anode; electrochemical measurements are used to determine polarization resistance and overpotentional like a function of current density. The structural and optical characterization by XRD, AFM, SEM, XPS and SE indicate crack free structures with good adhesion. Keywords: Ceramic thin films, 20Ni-SDC/8YSZ, PLD, Cubic Fluorite Structure, Electrochemical devices.

Resume : Due to the rising problem of diabetes as well as the increasing number of people monitoring glucose level during exercises, new developments in the field of glucose sensing are needed. Among different sensors, electrochemical ones seem to be of a particular interest, as they are highly reliable and sensitive. In our studies, we propose the active element of such sensor that is based on structured titanium foil covered with Au nanoparticles, which are formed out of ultra-thin metallic layers by means of nanosecond laser dewetting that can be easily scaled up. Application of different laser working parameters (?: 266, 355, 532 nm; fluencies: 15-90 mJ/cm2) enables to obtain a variety of gold nanoparticles configurations confirmed by scanning electron microscopy inspection. Proper optimization of these parameters lead to formation of Au-Ti structures that are characterized by twice as better response than furnace dewetted Au nanoparticles over Ti structured foil [1]. Moreover, the selectivity and mechanical stability of prepared material is maintained. Electrochemical tests in the presence of human serum as well as in artificial sweat and saliva were performed to verify the possible application of electrodes in the real conditions. Obtained results confirmed that fabricated material may be beneficial in future commercial devices. Research is financed by NCBR via LIDER/2/0003/L-8/16/NCBR/2017 grant. [1] Olejnik et al. Electroanalysis 31 (2019) 10.1002/elan.201900455

Resume : Semiconductor oxides are among the most widely studied materials in view of gas sensor application due to their remarkable physical, optical and optoelectronic properties. One novel approach to modifying and improving the performance of a semiconductor oxide as gas sensing material is forming a composite with other semiconductor oxides, i.e. combining the advantages of both components into a single composite material. Another approach to improving the gas sensing performance of these materials is producing a nanostructured morphology to increase the surface area. An efficient way of overcoming the higher operating temperature as a disadvantage of the metal-oxide sensors is illuminating their surface by ultraviolet or visible light. In this work, we report fabrication of highly porous metal-oxide nanocomposites by pulsed laser deposition performed in air at atmospheric pressure. The technology applied leads to formation of nanostructures composed of nanoparticles. The attention was focused on the structure, morphology, composition, and optical properties of ZnO-TiO2 metal oxides. Results on the gas-sensing properties of the nanostructures with different composition are reported. The effect was investigated of the light irradiation on the response and time of response and recovery of the sensor elements. The gas sensing properties of the samples were compared under light irradiation at different wavelengths.

Resume : Recently, the focus of investigations in the field of nanoscience and nanotechnology is in designing nanomaterials that integrate two distinct functionalities into a single unit; for example, systems consisting of a magnetic material and metal-oxide semiconductor. This paper presents experimental results on fabrication of hybrid nanostructures composed by magnetic and metal-oxide nanoparticles. The samples are produced by a single-step process of pulsed laser deposition carried out in air at atmospheric pressure. One part of the depositions is performed by laser ablation of two metal or metal oxides targets: Fe–Zn, Fe–Ti and Fe2O3–ZnO, Fe2O3–TiO2. Other part of the experiments includes depositions from mixed targets of iron oxide and ZnO as well as iron oxide and TiO2 with different ratio between the target materials. Depositions are also performed in a magnetic field in order to control the morphology of the hybrid nanostructures. The laser ablation is carried out by nanosecond laser pulses delivered from Nd:YAG laser system working at its fundamental wavelength of 1064 nm. The structure, morphology and optical properties of the obtained structures are studied in relation to the sample’s composition. An analysis on the magnetic properties of the hybrid structures is also performed. The obtained nanostructures could be used in the design of novel magneto-optics and sensor devices.

Resume : Thin films of electrochromic (EC) materials are being considered for energy saving platforms. However, manufacturing high quality EC films, of superior stability and high coloration efficiency available and persistent in diverse conditions of temperature and/or illumination is challenging. Herein we proposed to create the next generation of EC hybrid thin films with controlled thickness and uniformity. Our model system incorporates tungsten trioxide and graphene and uses a Matrix Assisted Pulsed Laser Evaporation (MAPLE) method for the proposed controlled synthesis. The obtained hybrid thin films were characterized for their chemical and physical properties using Fourier Transform Infrared and energy dispersive spectroscopy, X-Ray diffraction, and optical and atomic microscopy respectively, while changes in their electrochemical characteristics were evaluated using cyclic voltammetry. It was found that hybrid films characteristics could be controlled by the MAPLE deposition conditions. It was also found that the obtained films have enhanced electron transport capabilities thus possibly providing lower resistance pathways at their interfaces. It is expected that our work could provide a user-controlled synthesis and manufacturing strategy to lead to thin films formation that have minimum interfacial defects while possessing maximum conversion efficiency to influence and/or dictate the energy saving profile of EC materials.

Resume : In this work, poly(N-isopropylacrylamide) (pNIPAM) derivatives (amine, azide and amide terminated pNIPAM) termoresponsive coatings were studied and correlated to MSCs behaviour. The surface properties of pNIPAM based coatings, especially their hydrophobic/hydrophilic character, as well as the thermoresponsive capacity were tuned by strict control over MAPLE parameters depositions and target composition. The chemical functionality was kept for all the samples obtained by MAPLE and the thermoresponse was demonstrated by the change in the contact angle and thickness values when the temperature was shifted from 37°C to 24°C for all the materials tested, with a smaller change for maleimide terminated pNIPAM. Biological assays performed in vitro (fluorescence microscopy and Scanning Electron Microscopy (SEM)) confirmed the conditioning of the early mesenchymal stem cell (MSC) growth by specific chemistry of the coatings. The cell imaging analysis revealed no cytotoxic effect of pNIPAM surfaces irrespective of type of functionalization.

Resume : Nowadays, the development of organic photovoltaics cells (OPV) with high efficiency is an interesting research challenge. Generally, the performance of OPVs are related to the materials, design and/or manufacturing process. A limitation is caused by the fact that many more organic compounds show p-type than n-type conduction. Usually, due to its high mobility, the fullerene C60 was utilized as electron transport material in the OPVs. However, taking into account its low solubility, many attempts were made to replace C60 with non-fullerene compounds. Thus, in the present study, bulk heterojunctions thin films based on perylene tetracarbxidiimide (PT) derivative compound as acceptor and zinc phtalocyanine (ZnPc) as donor were deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. In order to select the films with the best properties, the mixed active layers have been prepared using various ratios between the two organic components. The deposited MAPLE layers were investigated from structural, morphological, optical and electrical point of view using X-ray diffraction, scanning electron microscopy, atomic force microscopy, UV-Vis spectroscopy, photoluminescence spectroscopy and I-V measurements, respectively. The results emphasized that such organic heterostructures prepared by MAPLE technique can be integrated in photovoltaic devices.

Resume : Doped or un-doped SPIONs have been used in several studies for related applications due to their magnetic properties; mainly their capacity to be controlled by an external magnetic field. The paper reports the synthesis of iodine-doped iron oxide nanoparticles using a CO2 (10.6µm) laser pyrolysis technique starting from iron pentacarbonyl and methyl iodide as iron and iodine precursors, respectively, and ethylene as laser energy transfer agent. A flow of synthetic air was also added in the reactive mixture in order to generate iron oxidation in the reaction flame. The morpho-structural properties have been determined using the following techniques: X-ray Diffractions (XRD), Energy-dispersive X-ray spectroscopy (EDS), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Mössbauer spectroscopy, and hysteresis loop at room temperature. The as synthesized NPs were designated for biomedical applications including contrast agents and radiotherapy; from these reasons preliminary tests regarding their cytotoxicity were performed. The present study aimed at two complementary directions: first, to evaluate the cytotoxicity of the NPs and second, to evaluate if the treatment with these agents could induce an inflammatory response in macrophages.

Resume : Modification of the near-field properties of the nanostructures is an essential task for such practical applications as the control of radiation of nanoscale light sources or sensing. The properties of oligomers can be finely controlled during the fabrication stage or by controlling the excitation light during the experiments. However, on-demand tailoring the optical response of the oligomer structure after fabrication is still a severe challenge. Here we both experimentally and numerically demonstrate the pronounced modification of the near-field pattern in hybrid gold-silicon oligomers by femtosecond laser reshaping. We study the optical properties for different degrees of fs-laser-induced modification of oligomers by visualizing it with an aperture-type near-field optical microscope and by measuring scattering spectra (for far-field properties). The near-field distributions exhibit significant changes within 720–780 nm spectral range. This effect correlates with a moderate redshift of the broadband magnetic dipole resonance of the structure that occurs upon even a slight reshaping of the gold component of the oligomers. The proposed near-field reconfiguration approach makes hybrid oligomers a promising platform for nanoscale systems with an engineered enhancement of the near-field distribution in metadevices for optical data recording sensors, and biomedical applications.

Resume : Metallic nanoparticles find application in a large number of fields due to their interesting properties, which might be tailored and boosted by the alloying of several metals. The combination of five metals or more forming a solid solution is known as a High Entropy Alloy (HEA) due to their large mixing entropy. The fabrication of HEAs is still challenging in terms of bulk materials and their downsizing to the nanoscale remains quite unexplored yet. Furthermore, the fabrication of alloy nanoparticles usually involves complex wet chemical methods that seldom exceeds more than three metals. Solid State Dewetting (SSD) of metal films is a straightforward route for the fabrication of nanoparticles and is driven by minimizing the surface energy of the metal and the interphase energy between the metal and the substrate. This method has been extended so far to the fabrication of alloy nanoparticles from bi- and tri- layers of different metals by thermal annealing.1,2 In this work we present the fabrication of HEA nanoparticles by the SSD of sequentially deposited layers of Co, Cr, Cu, Fe and Ni. These metals were chosen attending to minimize the intrinsic strain of the HEAs and the stacking order regarding to minimize the surface energy and easily induce the SSD. The samples were treated by rapid annealing and a subsequent fast cooling since at high temperature the mixing entropy dominates the formation of a HEA. (1) J.Appl.Phys.2014,116(4),044307 (2) J.Mater.Chem.2012,22(12),5344

Resume : Pulsed laser deposition (PLD) which uses direct laser irradiation of organic molecules may induce pyrolysis and photo-chemical decomposition. A suitable choice is the MAPLE (matrix-assisted pulsed laser evaporation) technique, to develop multilayered thin films and / or embedded structures, when noncompatible solvents are available. The new 'push-pull' donor (D)-acceptor (A) chromophores developed is connected to a system of aromatic rings and azo groups which contributes to the delocalization of the pi-electrons, to obtain classic structures with optical response due to large hyperpolarizabilities that arise from a combination of strong electron-donating groups and strong electron withdrawing groups positioned at the opposite ends of a conjugated system. The azo thin film samples are investigated for their optical, morphological and chemical structure, i.e. by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and spectroscopic-ellipsometry (SE). To demonstrate the second harmonic generation (SHG) potential of such azo-chromophores, a pulsed femtosecond Ti:sapphire laser (80 MHz repetition rate, 800 nm, 100 fs) is employed. The pure response of azo-molecules to the electronic excitation can be resolved in contrast to the measurements on SiO2.

Resume : Pulsed laser deposition (PLD) of thin films has been proven for some time to be extremely versatile, despite the high price of equipment. The laser wavelength, the energy per pulse, and the spot size are some of the parameters that one can play with in order to obtain thin films with a wide range of properties and possible applications. Also, the number of pulses sent to the target in order to release the material to be deposited on a certain substrate plays a very important role for the films to be prepared, along with the nature and temperature of the substrate. This paper presents the spectacular variation with laser pulse number (N) of the optical properties of semiconducting bismuth oxide thin films prepared by PLD through the ablation of pure bismuth targets in oxygen atmosphere and onto Si/Pt substrates kept at room temperature. Thus, the reflectance of the films changes by dropping significantly when irradiating the target by 60 000 pulses vs. 40 000 pulses, while the refractive index (n), a key parameter, drops with increasing pulse number, hence with the films thickness. Still, the film roughness doesn't change significantly when the number of pulse are increasing, in spite of the general knowledge that the optical properties and roughness parameters are strongly related. Wemple-DiDomenico model was employed as one of the few models explaining of the energy bandgap of this type of films deposited onto opaque substrates, such in the case of conductive Si/Pt. The films exhibit strong anomalous dispersion, still the model can be applied on portions, showing that the bismuth oxide they are made up of a mixture of nonstoichiometric oxides and polymorphs of bismuth trioxide, especially in the case of the film prepared with 60 000 laser pulses. The mixed composition and structure which is typical for bismuth oxide films corresponds to several well-distinctive bandgaps, one for each different oxide within the films in pristine intermediate oxidation state, prior to structural and compositional stabilization. The paper has not only theoretical value, but also applicative features, since precisely the complex energy bandgap makes this kind of complex composition film proper for optoelectronic applications within several spectral domains.

Resume : We report on MnZn-type soft ferrite thin films grown on single crystal MgO substrates with various crystallographic orientations, i.e. (100), (110) and (111), by pulsed laser deposition (PLD). Their crystalline and magnetic anisotropy is investigated with respect to the chemical composition and phase. First, the morphological, structural and chemical composition of the ferrite are presented and discussed. The results reveal that high quality MnZn hetero-epitaxial thin films are grown, following the substrate's crystallographic orientation. Subsequently, the hysteresis loops are recorded and the open magnetic circuit measurements are corrected, by employing demagnetization factors by taking into consideration the local magnetic susceptibility. Finally, the hysteresis losses are estimated by the Steinmetz approach and the results are compared with available commercial information provided by selected ferrite manufacturers. Finally, the results are corroborated as the films are tailored for applications in high frequency devices, i.e. of up to several MHz, in low-to-medium power modules, and an efficiency of ~ 97-99%.

Resume : We develop functional surfaces of laser-microstructured Si, spin-coated with thermoresponsive PS/PNIPAM polymer blends and we study their switchable wetting behavior between hydrophilicity and hydrophobicity upon heating. PNIPAM is a thermoresponsive polymer, which is hydrophilic below 32oC and hydrophobic above 32oC. We take advantage of the large specific area and roughness of the micro-Si substrate to enhance the PS/PNIPAM film thermoresponsiveness. Microstructured Si substrates were fabricated by ns laser irradiation in SF6 gas. PS/PNIPAM blends, of various blend ratios, in THF were spin-casted onto flat and micro-Si substrates, with or without a native SiO2 layer. The wetting state of PS/PNIPAM films was determined by water contact angle measurements. The morphology of the surfaces was mapped by SEM and the chemical composition by EDS and micro-Raman spectroscopy. The depth-resolved chemical composition of the polymer films was provided by XPS. Upon heating, films on micro-Si switch from hydrophilic to hydrophobic. The transition is reversible for multiple heating/cooling cycles. Films casted on flat silicon do not undergo switching of their wetting behavior, even though they respond moderately to temperature. When films are casted on silicon with native SiO2, they show higher thermoresponsiveness, compared to substrates without SiO2. XPS reveals this is due to the arrangement of PS and PNIPAM in the films, depending on the presence or absence of the underlying SiO2.

Resume : Laser-induced forward transfer (LIFT) is a direct-write method used to print materials from liquid suspensions. Almost all kinds of inks, independently of their viscosity value and loading particle size, can be printed by means of LIFT since it is nozzle-free. This is beneficial for printed electronics applications since high solid content inks, like those employed in screen printing (SP), can be transferred digitally. These inks exhibit a high-viscosity due to the strong interaction in the highly packed arrangement of particles related to the elevated loading contents, which normally results in shear-thinning behaviors. Thus, these properties make SP inks unprintable using other already established direct-write technologies such as inkjet printing. In this work we studied the printing of continuous stable interconnects of commercially-available SP inks by means of LIFT. First, we printed single voxels by varying the main transfer parameters such as the laser pulse energy or the donor-receiver distance, which reveals a rather linear relationship between the voxel volume and the pulse energy for low energies and small gaps. Then, we changed the overlap between adjacent voxels in order to obtain uniform continuous lines and areas. A time-resolved visualization experiment of the transfer mechanism helps to correlate the printing results with the observed trends.

Resume : We report the synthesis and characterization of a series of alkali-doped (Li, Na, K and Cs) iron oxide nanoparticles using nanomaghemite obtained by laser pyrolysis (from Fe(CO)5 vapors) which were impregnated with Li citrate or Na, K, Cs nitrates salts followed by 500°C thermal annealing. The powders were characterized by XRD, EDS, SEM, TEM, FTIR and/or XPS techniques, revealing the presence of hematite/maghemite phases. They were deposed from aqueous suspensions as washcoat layers inside coridierite monoliths channels and the resulted dry supported catalyst were tested with promising results for the selective catalytic reduction (SCR) of NOx with ammonia using Diesel engine exhaust simulated mixture.

Resume : The fundamental wavelength and the second, third and fourth harmonics of a Nd:YAG nanosecond pulsed laser system are used to produce nanoparticles by pulsed laser ablation of a noble metal target immersed in double distilled water. An external dc electric field directed at different angles to the direction of the laser beam propagation is applied to study its impact on the morphology of the created nanoparticles by varying the electric field strength and the laser fluence. The profile of the optical transmission spectrum is used to indirectly assess the morphology of the ablated material. The nanostructures obtained are visualized by transmission electron microscopy (TEM), and their microstructure is studied by high-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED). Noble metal nanoparticles are expected to find many applications; among those, the biomedical uses and surface enhanced Raman spectroscopy are of particular importance, where controlling the nanoparticles’ shape is a major way of optimizing their effect.

Resume : Nanosecond laser annealing (NLA) is expected to be the next generation of thermal treatments in microelectronics. NLA, especially in the melt regime, enables dopant activation at record high concentrations. The melted depth is controlled by the laser energy density (ED). NLA can be performed in a step and repeat mode or by scanning the surface. At the edges of the beam, laser intensity intercepts melting threshold conditions at which surface roughness reaches a maximum. To understand and minimize it, we investigated the behavior of Si and SiGe surfaces upon NLA around the onset of melt. Si1-xGex epilayers (0 ≤ x ≤ 0.4) were submitted to NLA in a SCREEN LT3100 platform with a XeCl laser (308 nm wavelength, ~100-200 ns pulses). Laser ED range was chosen in order to investigate the various annealing regimes from sub-melt to full SiGe layer melt, with a focus on the melt threshold region. Samples were characterized by SEM, TEM, AFM and Energy Dispersive X-Ray analysis. For the first time, we evidenced that, when increasing laser ED around the melt threshold, there was, on Si and SiGe surfaces, more and more molten islands that merged into a continuous molten layer, in the end. Such isolated nanostructures were typically 50-400 nm wide and their morphology depended on the crystal orientation and the surface preparation prior to NLA. Leveraging Ge segregation towards the surface during the melt of SiGe, we also extracted their total height and depth beneath the surface.

Resume : Nanosecond pulsed laser ablation in liquids is utilized to create novel nanocomposite materials based on titanium with added Ag, Au, Pt or Pd. These materials implemented in different modifications as alloys, core-shell or dumb-bell like structures are intended to find application in, e.g., photo-catalysis, biomedicine, etc. The fundamental wavelength and the second, third and fourth harmonics of a Nd:YAG laser system are used as an ablation source. The target materials are different and correspond to the specified nanocomposite. The appropriate laser wavelength is chosen depending on the morphology of the nanocomposite we seek to obtain. Changing the composition of the nanocomposite and its morphology is achieved by controlling the energy density of the laser radiation at a given wavelength. The product of the ablation process is an aqueous colloid of the respective nanocomposite. Indirectly, the changes in the nanocomposites’ composition and morphology are monitored by the changes in the profile of the colloids’optical transmission spectra. Transmission electron spectroscopy (TEM) is used to visualize the shape, size and size-distribution of the nanocomposite particles. Their phase composition is evaluated using high-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED).

Resume : Attacks on national security of different European states as well as on the lives of their citizens have become a daily reality. Explosives and precursor materials are used in most of these attacks, which lead to the need for new detection solutions and technologies. Explosives are chemically unstable materials difficult to detect due to the low vapor pressure, therefore, novel devices and detection systems based on fully integrated arrays are of interest. In this work, we are focusing on fabricating sensor arrays based on chemiresistive sensors with proven sensing functionality for volatile organic compounds such as ammonia, acetone, and ethanol. The active materials in the sensor arrays are based on carbon nanotubes (CNT) and functionalized carbon nanotubes. For the fabrication of the sensor arrays, laser induced forward transfer (LIFT) is applied to transfer CNT pixels onto metallic electrodes. The distribution of the CNTs onto the metallic electrodes is investigated by scanning electron microscopy. Raman spectroscopy is used to check for any chemical modification in the transferred materials. Finally, the sensing characteristics, i.e. sensitivity, response and recovery times, selectivity are evaluated for the CNT and functionalized CNT based sensor arrays. Following these results one can envision that active sensing materials based on CNTs can be applied in explosive sensor arrays using laser technique. Acknowledgement Financial support from UEFISCDI, though the “Fabrication, calibration, and testing of advanced integrated sensor systems aiming at applications in societal security (TESTES)” project is gratefully acknowledged.

Resume : Polymer nanocomposites attracted a great interest not only for academic studies but also in industry side because of their cost/properties, energy/properties and weight/properties profiles useful for improved or novel mechanical, optical and physic-chemical properties, thermal stability, reduced gas permeability and in particular, in the area of flame retardancy. A serious drawback of using neat polymers in several applications is their high heat and smoke generation and possible toxic gases release. To improve the thermal and the thermo-dynamic mechanical properties during plasma transport, the adhesion of the coatings, the chemical groups availability on the coatings surface (i.e. polar or non-polar character) and the suppression of potential gas release, suitable additives were added. Used as thin coatings such polymer nanocomposites will convey improved protective properties to the materials they covered. We used pulsed laser deposition (PLD) to obtained polymer nanocomposites coatings. Two types of condensation polymer matrix were used, one based on ethylene-co-vinyl acetate copolymer (EVA) and a polyamide homopolymer (PA) As inorganic additives an Mg-Al layered double hydroxide (LDH), two organo-modified Mg-Al LDHs, a Mo-modified Mg-Al LDH and graphene oxide (GO) were used. The polymer nanocomposites obtained either by compression moulding or by injection moulding were used as targets for PLD deposition. The coatings were deposited on different substrates at room temperature using an Nd:YAG laser operating at 532 nm and 1064 nm wavelengths. The morphological, chemical –structural characteristics and functional properties of the nanocomposites based on EVA and PA polymers, targets and derived coatings, were screened using the usual techniques (XRD, SEM, AFM, and FT-IR, DRIFTS, UV-Vis, and Raman spectroscopy).

Resume : We report on the pulsed laser deposition (PLD) synthesis of four batches of TiO2 coatings in different gaseous atmospheres (O2, N2, Ar și He) as photoanodes in the structure of dye-sensitized solar cells (DSSC). Two TiO2 layers were deposited for each batch (a thin nanostructed one and a high density one) by using a KrF* excimer laser (λ= 248 nm și τFWHM = 10 ns) and applying a 10 and 40 Hz laser repetition rate. The morphology, topography and crystalline structure of the coating were evaluated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-Ray Diffraction (XRD), respectively. Depending on the ambient gas pressure during the PLD depositions, the SEM micrographs revealed morphological differences between samples. Furthermore, the AFM results are in good agreement with the SEM ones. The crystallographic assessment of the TiO2 samples highlighted the presence of a mixture of anatase and rutile with low crystallinity. The photovoltaic performance studies were carried out to understand and evaluate the effect of the TiO2 bilayer (the interaction with the dye molecules) on the cells efficiency.

Resume : In order to operate with high-power lasers, it is necessary to have high performing and resistant optics. The aim of this work is to test the resistance of antireflection coatings that can be used for ultra-short high-power lasers beam delivery/handling systems. At the present time, one of the biggest problems when operating high power lasers is the systematic damage coatings applied to various optical components. The use of antireflection (AR) coatings reduces the unwanted reflections from surfaces, keeping only the desired component, for which the reflectivity can reach up to 99.99%. In order to have high reflections for a range of wavelengths and diminished (antireflection) for another range, some more elaborate mirrors were developed. Generally, the optical coating is a dielectric material (e.g. metal oxide) deposited as thin film on optical support (quartz). The antireflection coatings are based on multi-layers with different refractive indices by pulsed laser deposition (PLD). The materials that were used are cheap and have repeatedly demonstrated their efficiency for this purpose: Hf, Al and Si oxides. In the frame of this work, heterostructures formed from 5 to 7 different layers should be tested to ultra-short high-power laser beam in order to determine the LIDT values and to advance their applicability in ultra-high peak power facilities.

Resume : This work presents the preparation of tin oxide and titanium dioxide nanoparticles using laser pyrolysis (LP) technique followed by the decoration of these nanoparticles with noble metals using chemical impregnation method. Sensitized mixtures of TiCl4 and SnCl4 precursors were used in the presence of oxygen in order to obtain nanoparticles of semiconductor oxides through laser pyrolysis method. The noble metal decoration was started using chemical impregnation of the collected materials with the aqueous solution of noble metal precursors (AgNO3, KAuCl4), to improve the functional properties of oxide semiconductors. Structural, morphological and optical properties of the obtained decorated nanopowders have been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, energy-dispersive X-ray spectroscopy (EDX) and UV–vis diffuse reflectance spectroscopy (DRS) techniques. The sensory and photodegradation properties of nano-oxides decorated with noble metal were tested, showing that for the photodegradation of perchlorethylene (PCE) carried out under UV-VIS light irradiation, the presence of noble metals on the TiO2 surface drastically improves the photocatalytic activity, especially if Au is used. Adding noble metals on the surface of the e oxide semiconductors nanoparticles has been proven to be an effective strategy to enhance functional properties of these materials.

Resume : Searching new types of environmental friendly piezoelectric materials is an important tendency nowadays for replacing materials currently used that contain toxic elements such as lead. One of the key materials that has proven by latest research to be a good candidate for replacing lead-based materials is (Ba1?xCax)(ZryTi1?y)O3 (BCZT) due to the strong piezoelectric response and its high dielectric constant. From the point of view of the piezoelectric activity presented in volumetric form, the BCZT solid solution with perovskite structure exhibits similar or even higher piezoelectric coefficients values as compared with the most used lead based compound-PbZrTiO3. The use of ecological piezoelectric thin films in acoustic sensors is very important especially in disposable electronics or food industry. We report obtaining SAW sensors based on strain engineered BCZT epitaxial films. The BCZT thin films with various stoichiometries (x= 45, 50, 55) were deposited using Pulsed Laser Deposition technique on STO or GSO substrates aiming at varying both induced strain level into the films and the compositions. The films thus deposited were studied by different techniques. The SAW tests were performed by applying an electrical signal to one of the transducers to generate a surface acoustic wave, which was subsequently transformed into an electrical signal. The functional characteristics of the SAW devices are discussed as a function of film?s compositions and induced structural strain.

Resume : Bismuth ferrite (BiFeO3) is the only known material exhibiting good simultaneous ferroelectric and antiferromagnetic orderings at room temperature, having a distorted rhombohedral perovskite crystal structure. This material is the basis for a wide range of applications in different fields, one of the promising applications for BFO materials being the photodegradation of organic pollutants. A variety of techniques are known for obtaining nanostructures, with different advantages and disadvantages. A simple and versatile technique is laser ablation in liquid. Using pulsed laser ablation in liquid-PLAL technique, we have synthesized different type of nanostructures of BiFeO3 based materials by varying the working parameters. Laser wavelength demonstrated to be very important as single-crystalline sheets nanoparticles with a narrow mean-size distribution or a combination of the two have been obtained for different wavelengths. The average nanostructures size and morphology was estimated by TEM and the optical properties by UV-Vis spectrometry. In this study we present the results of using pure BFO and rare-earth elements doped BFO nanostructures obtained by PLAL for rhodamine B degradation. Comparisons have been made between suspensions with different concentrations of nanostructures, as well as different rare earth dopants (Y, La). It was observed that the nanostructures obtained by laser ablation in the liquid have a high photocatalytic efficiency, and a good response over time

Resume : The multiferroic perovskite materials with low band-gap are very attractive for photovoltaic and photocatalytic applications. One of the most investigated multiferroic ABO3 compound is bismuth ferrite (BiFeO3) with a value of bandgap 2.7-2.8 eV. Through doping with rare earth elements (Yttrium, Lanthanum, etc) in different concentration the bismuth ferrite bad gap can be lowered from 2.7 eV to 1.9-2 eV. K:BFO is a recently identified multiferroic, derived from perovskite BFO with a A2B2O5 crystalline structure (brownmillerite). In the KBFO structure, the Fe2O3 block alternates with KBiO2 block (BO6 octahedra with BO4 tetrahedra). In this work, we report the optical properties of thin films of KBFO deposited by pulsed laser deposition method (PLD) on different substrates: Pt/Si, SrTiO3, Nb doped SrTiO3, SrRuO3/SrTiO3 and GdScO3. A parametric study on the influence of deposition parameters on the optical properties of the thin layer was carried out. Crystallinity properties and topography of surface of thin films were studied using X-ray diffraction, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The optical properties were determined by spectroscopic ellipsometry (SE) in the 250-1700 nm range of wavelength and the values of band gap (Eg) where determined from Tauc plot. The obtained value of band gap is in the range of 1.59 to 2.1 eV and depends on substrate nature.

Resume : Perovskite nanomaterials are of great interest in the 21st century. They are widely explored for optoelectronic devices, photovoltaic and light emission applications. Furthermore, they can be used as thermoelectric and magnetic materials and they are useful in multicolour biological imaging. Ferrite materials show numerous captivating properties correlated with strong absorption of visible light which recommend them as excellent candidates for reactions such as: water photodecomposition and photodegradation of organic pollutants. Lanthanum orthoferrite (LaFeO3) has perovskite structure and it can exhibit ferroelectric and ferromagnetic properties similar to BiFeO3. It can be used for numerous applications such as electrodes for fuel cells, chemical sensors, optoelectronic devices, catalysts and photocatalysts. Bulk LaFeO3 is considered to be an antiferromagnetic material with a very high Neel temperature. In photoelectrochemical applications, it is very important for the material to absorb light in the visible region. LaFeO3 is a material having an optical band gap ~ 2.07 eV with the absorption capacity mainly in the visible region of the spectrum and it receives considerable attention due to of its strong photocatalytic activity. In this study, LaFeO3 thin films were deposited via pulsed laser depositon (PLD) technique. Their optical properties were analysed according to: the used oxygen pressure during the deposition process; the used substrate for deposition; the number of laser pulses.

Resume : II-VI semiconducting thin films have become a great part of research interest due to their possibility to use in a wide range of device applications with their remarkable optoelectronic properties as ideal direct band gap, high absorption coefficient and photosensitive behavior in the visible region of spectrum. Based on these optical and electrical properties, these compounds have been investigated as an alternative material system in the fabrication of low cost optoelectronic devices and used as promising materials for the development of current technological devices. Among these compounds, zinc selenide (ZnSe) thin film has long been popular in the field of optoelectronics due to their high transparency in visible region, direct and wide band gap value, photoconductivity, high electron affinity and n-type semiconducting behavior. Although this type of films has potential applications in fabrication of light emitting diodes, thin film transistors, gas sensors, photodetectors and solar cells, in recent years, attention has been directed to alternative methods as variations in chemical constituents, doping, formation of ternary analogues, surface patterning in order to manipulate the material characteristics of thin films to improve the performance of the devices. In this study, ZnSe thin films were deposited on a soda-lime bare glass substrates using direct electron-beam evaporation of high purity and stoichiometric ZnSe powder at room temperature. Bare glass substrates were used in thin film characterization processes and also employed to tailor its optical properties for possible device applications. For the deposited ZnSe thin films, energy dispersive X-ray (EDS) analysis showed an average atomic percentage of ZnSe is near to stoichiometric composition of the source material as Zn:Se ratio (50:50). The X-ray diffraction profile of the samples was indexed according to JCPDS files and the characteristics diffraction peaks were observed in a good agreement with the literature without any formation of secondary phase in the structure. The surface imaging using scanning electron microscopy (SEM) and detailed surface morphology analysis by using atomic force microscope (AFM) showed that the deposited ZnSe thin films are dense and compact in nature. From the optical transmission studies, films were found in direct optical transition characteristics and the band gap values of the samples were calculated using Tauc plots. In addition, substrate-assisted laser patterning was investigated as an alternative technique to create functional structures for possible optoelectronic applications. The straight and continuous line patterns on bare glass substrates were optimized in terms of pulse repetition rate, laser power, pulse energy and the feeding speed of the nanosecond pulsed Nd:YAG laser system. Uniform periodic pattern without any damage to the glass substrates were achieved with a wavelength in the infrared region. It was observed from EDS spectrum of the films that the stoichiometric transfer of material from source powder to the deposited films on different substrates with different line patterns was achieved. In the case of surface morphology, the effects of laser patterning on characteristics of the ZnSe thin films deposited on glass substrates were investigated by SEM and AFM images. UV/Vis spectrophotometer was used to discuss the transmittance and reflectance characteristics of these patterned samples.

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

Resume : This paper describes a rapid, solvent-free (laser based) procedure for the fabrication of sensitive sensors based on hybrid nanocomposites, i.e. single walled carbon nanotubes decorated with oxide nanoparticles that overcomes challenges associated with solvent-assisted chemical functionalization and integration of these materials into devices. In this work, we are focusing on fabricating sensor arrays based on chemiresistive sensors with proven sensing functionality for volatile organic compounds such as ammonia, acetone, and ethanol. The active materials in the sensor arrays are based on carbon nanotubes (CNT) and CNT decorated and/ or functionalized with oxide nanoparticles (for ex. SnO2). The oxide decorated CNTs are obtained by spin coating the oxide nanoparticle suspension onto the already grown CNT films. For the fabrication of the sensor arrays, laser induced forward transfer (LIFT) is applied to transfer CNTand oxide-CNT pixels onto metallic electrodes. The distribution of the transferred materials onto the metallic electrodes is investigated by scanning electron microscopy. Raman spectroscopy is used to check for any chemical modification in the transferred materials. Finally, the sensing characteristics, i.e. sensitivity, response and recovery times, selectivity are evaluated for both the CNT and oxide-CNT based sensor arrays. It has been found that the oxide-CNT arrays show a better sensitivity and a decreased recovery time (of approx. 20 seconds) than the CNT based sensor arrays. Following these results one can envision that active sensing materials based on CNTs and oxide-CNT can be applied in explosive sensor arrays using laser techniques. Acknowledgement Financial support from UEFISCDI, though the “Fabrication, calibration, and testing of advanced integrated sensor systems aiming at applications in societal security (TESTES)” project is gratefully acknowledged.

Resume : The interaction between ultrashort laser beam pulses (40 ps) with gadolinium-doped ceria (CGO) thin films induces the formation of surface micro/nanostructures. These laser-induced periodic surface structures (LIPSS), or ripples, play a very important role to improve the physico-chemical properties of thin films as specific surface. In the case of electrochemical cells made of thin film assembly, they can further enhance the performance of the electrode by increasing the reactions of the active species at the electrode/electrolyte interface. A Nd: YAG laser beam at the third harmonic (355 nm) is employed to irradiate a 4 X 4 mm2 upon the surface of CGO thin layer, that was deposited by magnetron sputtering. The morphological and clear features of the ripples were observed on CGO thin films by high resolution scanning electron microscopy (HR-SEM). LIPSS are generally produced in a low fluence laser multi-pulse regime close to the ablation threshold. They were obtained with the period of approximately 220 nm under appropriate values of laser fluence (F from 138 to 417 mJ/cm2) and scanning speed (1 mm/s to 5 mm/s). In agreement with literature, it has been noted that these periodic structures can be distinguished as function of their period, that we can classify as low spatial frequency LIPSS (LSFL) and high spatial frequency LIPSS (HSFL). In this work, we focus on the optimization of laser parameters to generate clear and high resolution LSFL/HSFL. Using numerical tools for SEM/AFM images, the enhancement of the specific surface will also be discussed.

Resume : The ability of microbial strains to grow in biofilms represents one of the main factors of persistent infections in hospitalized patients. Such multicellular attached communities could develop on medical devices and surfaces, causing implant failure and prolonged hospitalization. The aim of this study was to obtain laser modified bioactive surfaces containing graphene oxide and silver nanoparticles (NPs) with antimicrobial effect. The surfaces were obtained by MAPLE (matrix assisted pulsed laser evaporation) and physico-chemically characterized by DRX, DTA-TG, SEM and MIR. Antimicrobial effect was assessed against relevant Gram positive (Staphylococcus aureus and Enterococcus faecalis) and Gram negative (Pseudomonas aeruginosa and Escherichia coli) species. The results revealed that the obtained NPs present crystalline structure, nanometric size and low aggregation, while the laser processed coating is thin and uniformed when a fluence of 400 mJ/cm2 is applied. The nanomodified thin films demonstrated and increased potential to inhibit microbial colonization and biofilm development, being more active against Gram negative monospecific biofilm development. Our study reveals that the developed coatings could be applied for the development of new bioactive surfaces and devices with anti-biofilm effect.

Resume : 3D structures were produced by LDW via TPP in biocompatible photopolymers using fs laser at powers from 10 to 40 mW and scanning speeds from 10 to 100 µm/s. A parametric study was carried out for identification of the best combination of the two parameters for obtaining an accurate geometry control of the written structures as well as a high spatial resolution. The design of the 3D structures was calculated using Python 3.6.6. All information related to structure geometry is delivered as a list of carthesian points, appropriately configured for the 3D lithography installation (Nanoscribe Photonic Professional). The Python script also delivers a separate file that is used for setting laser writing parameters and also centralizing all geometry files.The study was focused on vertical microtubes with high aspect ratio that were used to improve the quality of the 3D structuring. Several phtopolymers suitable for biomedical applications were tested, such as IP-L780 and Ormocore. For each photopolymer, laser scanning speed/laser power maps were produced. The obtained structures were investigated in terms of morphology and aspect ratio. The optimum laser processing parameters were selected.

Resume : The drive to enhance human interactivity and reduce weight of electronic systems has led to the use of non-conventional substrates. As the substrates become thinner, more flexible and economical, the thermal stability of the working substrate is significantly lowered. As such, the conventional modes of component attachment are no longer functional. To bridge this gap, anisotropic adhesives and tapes, as well as low temperature solders and conductive epoxies, have been developed. However, in terms of performance, conventional soldering is still the champion. One way to combine traditional soldering techniques with thermally sensitive substrates is laser soldering. However, technical challenges, combined with the high costs of lasers, continue to create barriers to a broader adoption. This discussion focuses on PulseForge Soldering, which uses high intensity flash lamps to overcome the disadvantages of laser soldering, while enabling soldering on a wide range of substrates. Similar to laser soldering, photonic soldering utilizes selective absorption of light to enable conventional solders (such as SAC-305) to affix commercial packages (such as transistors, LEDs or resistors in traditional sizes) on the underlying thermally unstable substrate (such as PET, PEN or TPU). An innovative application for this process lies in the field of wearables. Sensors and actuators attached to commonly used fabrics could enhance health and wellness monitoring, as well as packaging and fashion.

Resume : Flash lamp annealing (FLA) is an innovative technology already used in semiconductor industry, for flexible electronics and for thin functional coatings on glass. Due to the short time scale in the milliseconds range, FLA is energy and time effective, suitable for temperature-sensitive substrates and allows the exploitation of non-equilibrium processes. Recently, FLA was combined with sputter deposition to improve the properties and the functionality of transparent conductive binary oxide thin films based on indium, zinc and titanium. In this contribution, we present a new approach assembling both technologies and we report on first experiments to fabricate thin poly-crystalline silicon films on standard glass and ultra-thin glass foils for potential thin film transistor application. However, the improvement of sputtered films by post-deposition treatment is a general issue in order to achieve the desired structural, optical and electrical properties. The functionalization on the millisecond time scale as well as our strategies avoiding thermal stress and minimizing defects in order to obtain layers with a low electrical resistivity are discussed in details.

Resume : Solid-state thin film batteries are promising power sources for microelectronics. The thin film cathodes in these batteries are typically annealed at about 700 °C in order to crystalize them into electrochemically active phases. This thermal treatment has several drawbacks such as evaporation of Li2O in cathodes at elevated temperatures which degrades the battery performance; need of thermally stable current collectors, e.g. Pt and being time consuming. Therefore, effective alternatives to thermal an-nealing are desired for the crystallization of cathode films. Photonic based methods such as xenon flash lamp annealing (FLA), ultra-violet excimer laser irradiation (UV-laser) and pulsed infrared laser (IR) annealing are shown to crystalize materials used in print-ed electronics and solar cells. In such methods, the thin film material is illuminated with short pulses of light sources and absorbs the photons whose energy is then converted into thermal energy. By these annealing approaches, the cathode films can be crystalized at apparently lower temperature in short time while the underlying current collect and substrate remain unheated. In this work, we explore the feasibility of using FLA, UV-laser and IR annealing for LiCoO2 and LiMn2O4 thin film cathodes. The effect of these methods is systematically compared to that of reference thermal annealing in terms of processing time, crystal structure and electrochemical performance of the cathode films. By certain methods and under optimal conditions, the annealed cathodes are crystalized at room temperature ambient in less than one hour, and showed capacity of up to 51 % of that of thermally annealed samples. A comprehensive comparison of the methods and results will be pre-sented in the talk.

Resume : In this work, we report a novel approach to fabricate the nano-hydroxyapatite (nano-HA)/zirconia (ZrO2) ceramic composites via an additive manufacturing process based on mask projection stereolithography (MPSL). The composites suspension characters and photosensitive parameters with different mass proportions of nano-HA/ZrO2 were investigated, the result demonstrated that composites suspension has lesser critical exposure (Ec) and higher penetration depth (Dp) as an increased proportion of HA, which confirms the variation tendency relating to viscosity and refractive index of composites suspension. The prepared green composites with nano-HA/ZrO2 ratio of 75/25 showed a higher density and compressive strength of 3.151g/cm3 and 7.29MP, respectively. The XRD analysis indicated that the nano-HA/ZrO2 composites sample consists of ZrO2 phase and TCP phase after sintered at 1500℃ with the decomposition of HA, still retaining the biocompatibility. Finally, test results illustrated the nano-HA/ZrO2 composites with the ratio of 75/25 have excellent manufacturing performance and microstructure to solve the manufacturing difficulty of conventional ceramic-shaping methods. The study may be referable for fabrication of other ceramic composites.

Resume : Bulk and thin film metallic glasses (MG) are considered valuable materials for niche markets in various domains such as biomedical, aeronautic and renewable energies. Their amorphous structure induces outstanding mechanical properties (Metal-like) and surface state (Glass-like). The objective is to explore the potential to modify the surface physico-chemistry for the enhancement of the MG functionalities. Ultrafast laser irradiation treatment can considerably increase the properties of the thin film coatings by creating surface structures named LIPSS (Laser Induced Periodic Surface Structures). Controlling the initiation and the positive feedback by adjusting the laser parameters (fluence, pulse number), femtosecond (fs) laser irradiation generates LIPSS with a large variety of scales and periodicities. Under a controlled irradiation, MG undergo a remarkable self-organization process exhibiting very regular and homogeneous patterns with few bifurcations. In this study, Zr-Cu thin film MG was irradiated by a fs laser in order to structure the surface by tailoring multiscale patterns and topographical architectures. Two main types of nanostructures with variation of contrast and periodicity are obtained and analyzed by microstructural characterizations such as SEM, AFM and TEM. These results obtained on binary alloys propose irradiation strategies to achieve surface functionalization of thin film MG improving physico-chemical features such as wettability and corrosion behavior.

Resume : Paper is a low cost and sustainable material that is gaining interest as substrate for printing electronic components and circuits. Inkjet printing is the most widespread direct-write method for printing electronics. In spite of its extended use, not all paper substrates are suitable for conductive inkjet printing inks. These exhibit low viscosity and nanometric loading particles that results in ink leakage and non-functional pads when deposited on regular paper such as paper sheets. Owing to this fact, paper must be coated with planarization polymer layers, despite this is less cost-effective and ecofriendly. As an alternative, we propose using laser-induced forward transfer (LIFT) for printing commercial conductive screen printing inks, which high viscosity and large particle size should avoid leaking and result in functional conductive patterns on regular paper. In this work we printed a silver screen printing ink on both coated and regular paper by means of LIFT. We first determined the optimum printing parameters (pulse energy, spot separation) to obtain continuous lines. Then, we considered a multiple-printing approach to increase the electrical performance, resulting in tens of microns thick lines with sheet resistances of 25 mΩ/sq. This value significantly improves sheet-resistance values of elements printed by inkjet and can be obtained even on regular paper. Finally, we printed a RF inductor as a proof-of-concept, which operates accordingly to the design parameters.

Resume : Plasmonic sponges are of interest in the field of nanophotonics due to the possibility of generating high local field enhancement through the large surface-to-volume ratio. One of the modern vectors for the development of this topic is the combination of a plasmonic nanosponge with semiconductor and all-dielectric materials, which is a rather non-trivial task. In this work, we suggest an application of the femtosecond laser ablation technique for fabrication of hybrid metal-dielectric nanostructures and an effect of laser annealing on them. Laser ablation of a bi-layer Au-Si film allows to obtain structures of plasmon gold nanosponges, the pores of which are filled with grains of crystalline silicon. TEM imaging is showed that diameters of sphere-like structures vary in the range of hundreds of nanometers and a silicon phase is crystalline. Numerical calculations of the electric field distribution in a hybrid nanosponge showed the possibility of the electric field enhancement in a wide range of wavelengths. We have demonstrated that such a structure can generate photoluminescence in a visible and near-infrared spectral range under multiphoton excitation. In addition, the positive effect of laser annealing on the photoluminescence generation of silicon is shown, which is accompanied by an increase in the peak of the optical phonon of crystalline silicon in Raman spectra and a general increase in the intensity of the photoluminescence signal from the nanostructure under identical excitation conditions. It is possible to find an application of hybrid nanosponges for the development of nanoscale sources of broadband radiation and for the modernization of the broadband scanning near-field microscopy.

Resume : Layared materials such as graphite and transition metal dichalcogenides have attracted lots of attention owing to their unusal nature of reacing atomic thickness. These so-called two-dimensional materials reveal outstanding physical properties when its thickness reduces to mono layer, such as indirect to direct bandgap transition for TMDs, which is ideal for different kinds of potential applications in optoelectronics, energy harvesting, Li-ion batteries and supercapacitors. Among the numorous TMDs, MoTe2 is the only TMD, which can be synthesized in two phases because of the small energy difference between them. However, the synthesis approach to control these two phases is not refined enough. Most reliable strategy is CVD process, but its require high temperature annealing for a long time while control the Te atomphere at the same time. These complicated process is hard to applied and high temperature also restrict the use of substrates. Therefore, further improvement of the synthesis methods is an important issue. Here, we use a laser approach to induce the MoTe2 growth directly on different substrates such as Quartz and sapphire and so on. We control the two phases by tuning the laser power and irradiation time. TEM supported by Raman and X-ray Photoelectron Spectroscopies confirm the existence and quality of the synthesized films. Furtheremore, this approach can be extended to the synthesis of other TMDs. The laser annealing assisted method develops a new approach that is fast, cheap, patternable and does not require transfer giving a step forward on the technology development for practical applications.

Resume : In previous works [1,2] it was proved that Laser Shock Peening (LSP) improves the high temperature (HT) oxidation resistance of pure Ti. Here, we address the understanding of this behaviour as the result of the different effects of the LSP treatment affecting both the surface and the volume of the metal. For this, the study was focused on the influence of the laser irradiance (varying around 9 GW/cm2), and the number of laser impacts (1 to 3). A microstructural study of the cross-section of the LSP treated samples was made by EBSD as a function of these parameters. Two types of twins are observed, with a specific location within the samples depth. Their density increases with the laser irradiance and number of impacts. The LSP treatment modifies the topography of the samples surface. Moreover, XRD results showed changes in the texture at the subsurface. Chemical modifications of the surface as a function of the laser irradiance were investigated by XPS and SEM/EDS. It was shown an increase of the surface contamination with the irradiance and number of impacts. The chemical environment during the HT oxidation was first studied by XPS and the results were further compared with those obtained by ion beam analysis. This shows a preferential location of nitrogen at the metal/oxide interface from the very beginning (up to 100 h) of oxidation. This insertion of nitrogen seems to play a role of barrier for oxygen diffusion. In addition, the twins produced by the LSP treatment can also contribute to a smaller penetration of oxygen within the metal [2]. Finally, the best LSP parameters are those limiting the chemical contamination of the sample and maximizing the structural modifications. Ref [1] A. Kanjet et al. Surf. Coat. Tech., 2017 [2] A. Kanjer et al. Oxid. Met., 2017

Resume : Raman and Tip-Enhanced Raman Spectroscopies (TERS) are very powerful techniques to investigate the electronic and molecular structure of nanoscale materials. First, we report on photochemical and photophysical properties produced by Surface Plasmon Resonance (SPR) on metallic nanograins by means of high resolution (TERS). We describe the local variation of plasmon-induced Raman enhancement on the surface of nanostructure that also affects the photochemistry near the functionalized tip apex. Our TERS maps with 10 nm spatial resolution show Raman modes of hot electron reduction of 4-nitrothiophenol molecules on the tip and indicate at least partial photochemical dimerization. An apparent photo-induced reversibility of this dimerization can be conservatively explained by a local topography feature that we simulate in a finite element environment. Second, we have studied the surprising pressure effects on luminescence spectra of a series of molecular chromium(III) complexes and compare with the well-established properties of doped solids. Luminescence and Raman spectra and their variation with external pressure are presented. The pressure-induced red shift of 11 cm 1/kbar in [Cr(bpy)3]3 and similar molecular compounds is higher by more than an order of magnitude than for chromium(III) doped oxides, widely applied as pressure sensors.

Resume : Application of laser stereolithography (SLA) was considered for the manufacture of functional lead-free piezoceramics from barium titanate. The process of layer-by-layer growing of preforms from a slurry consisting of a mixture of particles of barium titanate powder and a solution of photopolymer monomers was experimentally studied. The obtained preform samples were subjected to polymer binder removal processes and subsequent calcination at temperatures of 1100 and 1300 ° С. The microstructure of sintered samples and their phase composition were determined. The possibilities of obtaining billets from barium titanate by the SLA and obtaining sintered material without impurity phases in the composition are shown. The high density and mechanical strength of samples of 3D printed barium titanate ceramics strongly depended from optimal technological route, including the choice of the type and concentration of the monomer solution, the SLA process regimes, temperature-time modes of polymer binder removal and firing.

Resume : Development of advanced materials is always an important topic for global researchers. Meanwhile, the function/performance improvement of products is always accompanied by the development of advanced materials, especially the lightweight improvements. One of the advanced lightweight material is Sc- and Zr-modified Al alloy. The high specific strength of such materials is contributed by the precipitation strengthening effect and thus limits the formability through traditional processes. According to the development of 3D printing technologies, numerous mature high specific strength metal materials with complicated design were developed and applied to real applications such as aerospace parts and medical devices. In this study, Selective Laser Melting (SLM) technology has been introduced to fabricate Sc-modified Al alloy. Since the high strength of Sc-modified Al alloy is contributed by the fine grain size and precipitation strengthening effect, the strength can be further improved if the initial grain size can be made finer using 3D printing parameter optimization by exploring the relationship between parameter-microstructure-performance. In this study, the microstructure and mechanical property of 3D printed Sc-modified Al were examined/tested and the relationship between parameter-microstructure-performance was discussed in detail.

Resume : Tunable photonic crystals (TPC) are nature-inspired nanostructure whose response can be tuned with an external stimulus. There has been a great demand for such structures because of its wide applications in optically active devices, color displays, biological and chemical sensing. Hydrogel is a potential material for fabrication of TPC as it can exhibit a reversible response to an external stimulus such as humidity and heavy metals. Two-photon assisted polymerization (TPP) provides efficient control over the spatial resolution of fabricated features due to the non-linear laser-material interaction. Subwavelength resolutions can be achieved with ease in photoactive polymeric resin compositions using TPP. We have demonstrated the fabrication of biocompatible hydrogel-based TPC having different periodicities, using a nanoimprinted mold fabricated by TPP. Optical detection was employed to monitor the response of the fabricated TPC in the presence of various humidity levels and different concentrations of heavy metals. This technique provides an efficient way to fabricate TPC for wide range of materials and hence can be used to devise sensors for other stimuli as well. Keywords: Photonic crystals, Hydrogels, Sensor, Direct laser writing.

Resume : In this work, the effects of selective laser sintering on ceramic oxide powders were investigated. Different ceramic oxides (SiO2, Al2O3, ZnO, CaO, MgO, K2O, Na2O, Li2O) were dry mixed and ground in a planetary mill at 250 rpm for 30 min, with higher weight percentage of Al2O3 and CaO. The mixture of ceramic powders was irradiated with a continuous CO2 laser (λ=10.64 μm) with a power density of 155 W/cm2. The powders were irradiated in two ways: fixed irradiation and irradiation on moving samples placed in a translation device with two irradiation scans on the same sample (slow and fast irradiation), which were: 5 - 15 mm/s and 5 - 17 mm/s. The morphology, elemental composition, crystalline structure and thermal properties of sintered ceramic samples were studied by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and thermogravimetric analysis/differential thermal analysis (TGA/DTA). The SEM results, showed that the morphological changes depend on laser parameters, obtaining a sintered surface without porosity formation. XPS results, confirmed the chemical composition and chemical states of the corresponding elements. The XRD results revealed the formation of crystalline phases as anorthite, cordierite and magnesium aluminate spinel. In the thermal studies the formation of new phases was confirmed.

Resume : Oxide dispersion strengthened (ODS) steel is a promising structural material for high-temperature applications such as turbines and advanced nuclear reactors due to its enhanced resistance to irradiation, corrosion, and high-temperature creep. Production of ODS steel via conventional powder metallurgy faces challenges in maintaining uniform properties throughout the material combined with complications and high cost of fabrication. Selective laser melting (SLM) is a rapidly emerging technique that circumvents these problems by systematically melting the powder locally during the buildup. However, SLM involves extreme thermal gradients leading to complex microstructures during cool down influencing the properties of the material. The ODS dispersoids as well as the crystallographic phases present on the microscopic scale determine the macroscopic properties of the material. In this work we characterize the chemical microstructure of ODS steel produced by SLM. Powders produced from mechanically alloyed Fe-9Cr steel with 0.5% yttrium oxide were employed to print a cubic specimen using SLM. Pieces of the 3D printed specimen were formed into thin X-ray transparent thin sections using electro-polishing. Scanning- (SEM) and transmission electron microscopy (TEM) were used to characterize dispersoid morphology and distribution, revealing oxide dispersoids in the steel matrix with sizes down to 2 nm. Focused synchrotron hard X-rays were subsequently used for chemical and crystallographic characterization of the melt pools in the thin section. Understanding the interplay between chemical and crystallographic microstructures is key for optimizing materials manufactured by laser based additive manufacturing.

Resume : In this study, delafossite CuFe5O8 was prepared by a CO2 laser sintering method and characterized with crystal structure, surface morphology and composition using an x-ray diffractometer (XRD) and a scanning electron microscope (SEM) equipped with an x-ray energy dispersive spectrometer (EDS), respectively. SEM images revealed that the surface of laser-sintered CuFe5O8 can be divided into two parts based on their various cooling rates. The first part scanned by laser beams (valley) exhibits many tiny crystallites with a triangular shape and an average size of around 5 μm. The second part formed between laser scans (peak) presents smaller crystallites with porous structures and an average size of around 1.5 μm. XRD patterns presented a main phase of CuFe5O8 with a small amount of CuFeO2. Selected area electron diffraction patterns revealed that the d-spacing corresponds to the phases of CuFeO2 and CuFe5O8. As known from the phase diagram, a molar ratio of 1:1 for CuO and Fe2O3 precursors would generate a main phase of CuFe2O4. However, in this study, the process of CO2 laser sintering was carried out in ambient air without any gas injection. It is believed that the lasering will deplete the surrounding oxygen content and result in a phase transformation from CuFe2O4 into CuFe5O8. Electrical measurements of laser-sintered CuFe5O8 using two tungsten microprobes indicated a metallic conducting property. The detailed process and characterization will be presented in the conference.