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Pulsed laser deposition (PLD) represents a promising bottom-up methodology for the synthesis and transference of nanoparticles to the surface of a biomedical device. Silver (Ag) nanoparticles directly incorporated on the metallic implant emerge as an alternative strategy for local action against prosthetic joint-associated infections. In the present research, a dual sequential PLD process is proposed to obtain a bilayer coating with (1) a bio-derived calcium phosphate (CaP) layer, to provide osteointegrative properties and (2) the controlled growth of the Ag nanoparticles over it, ranging the number of laser pulses from 100 to 500. The characterization by SEM, EDS, TEM, XPS and AFM revealed the uniform deposit of Ag rounded nanoparticles, with a narrow mean size distribution, in the original non-oxidized metallic state. Moreover, given the evidences from XPS and AFM techniques, the occurrence of a coalescence phenomenon from 400 pulses onwards was proposed together with the expected positive linear relation between the number of pulses and Ag contribution with a deposition rate of 0.05 at. % of Ag per pulse. Conversely, the decrease in roughness as the Ag content increased was also verified. Finally, the expected bacteriostatic activity for these PLD deposited metallic state Ag nanoparticles against the bacterial strain Staphylococcus aureus was confirmed. Moreover, the evaluation of the osteoblast-like MG-63 cells viability on the Ag(100–500)-CaP coatings revealed a significant increased proliferation (p > 0.05) on the Ag100-CaP coating compared to the control (Ag0-CaP). When same coating was evaluated against S. aureus the effect was not significant. The possibility of modulating the amount of nanoparticles in the bilayer coating to obtain a greater or lesser effect in combination with CaP was revealed.

Deposition of Au nanoparticles (NPs) through UV ultra-short-pulse laser ablation in vacuum is a methodology suitable for obtaining high purity supported plasmonic NPs with a superb adherence to both planar and patterned substrates. Furthermore, the peculiarity that upon sub-picosecond laser irradiation NPs form directly within the target leads to narrow and controlled size-distribution. While extensive literature theoretically models phase changes and pressure relaxation of metal targets under sub-picosecond irradiation, the evolution of the nanostructured deposit through different ablation regimes is poorly documented experimentally. In this paper, besides modeling the temporal evolution of electron and lattice temperature following sub-picosecond laser pulse irradiation of Au bulk at the threshold ablation fluence (0.1 J/cm2), we report an accurate statistical, morphological and structural characterization of the AuNP distributions as a function of the laser fluence tuned from 0.1 to 3 J/cm2 to drive the target through two ablation regimes. The occurrence of photomechanical spallation and phase explosion at low and high fluence, respectively, is correlated with the evolution of the NP deposits, which are discussed by providing a physical insight in the interplay between fluence-driven ablation regimes of the target, arrangement kinetics of the deposited species (NPs and vapour species) and (crystalline or amorphous) phase of the NPs. This knowledge is key for controlling the surface plasmon resonance response of AuNPs depending on the designed application.

The ablation of a metal target at laser energy densities in the range of 1–10 TW/cm2 leads to the generation of nanoparticles (NP) of the ablated material. This aspect is of particular interest if the immobilization of NPs on three-dimensional (3D) substrates is necessary as for example in sensing applications. In this work the deposition of Au NP by irradiation of a Au bulk target with a sub-picosecond laser beam (500 fs; 248 nm; 10 Hz) on 2D (silica and Si(100)) and 3D substrates (silica nanowire forests) is reported for different number of laser pulses (500, 1000, 1500, 2000, 2500). A uniform coverage of small Au NPs (with a diameter of few nm) on both kinds of substrates has been obtained using a suitable number of laser pulses. The presence of spherical droplets, with a diameter ranging from tens of nm up to few μm was also detected on the substrate surface and their presence can be explained by the weak electron-phonon coupling of Au. The optical characterization of the samples on 2D and 3D substrates evidenced the surface plasmon resonance peak characteristic of the Au NPs although further improvements of the size-distribution are necessary for future applications in sensing devices.

In this work, yttrium (Y) thin films have been deposited on Si (100) substrates by the pulsed laser deposition technique. Ex-situ morphological, structural and optical characterisations of such films have been performed by scanning electron microscopy, X-ray diffractometry, atomic force microscopy and ellipsometry. Polycrystalline films with a thickness of 1.2 μm, homogenous with a root mean square roughness of about 2 nm, were obtained by optimised laser irradiation conditions. Despite the relatively high thickness, the films resulted very adherent to the substrates. The high quality of such thin films is important to the synthesis of metallic photocathodes based on Y thin film, which could be used as electron sources of high photoemission performance in radio-frequency guns.

193 nm Excimer laser assisted growth and crystallization of amorphous Si/Ge bilayer patterns with circular structures of 3 μm diameter and around 25 nm total thickness, is presented. Amorphous patterns were grown by Laser induced Chemical Vapor Deposition, using nanostencils as shadow masks and then irradiated with the same laser to induce structural and compositional modifications for producing crystalline SiGe alloys through fast melting/solidification cycles. Compositional and structural analyses demonstrated that pulses of 240 mJ/cm 2 lead to graded SiGe alloys with Si rich discs of 2 μm diameter on top, a buried Ge layer, and Ge rich SiGe rings surrounding each feature, as predicted by previous numerical simulation.

We report a design of photocathode, which combines the good photoemissive properties of lead (Pb) and the advantages of superconducting performance of niobium (Nb) when installed into a superconducting radio-frequency gun. The new configuration is obtained by a coating of Nb thin film grown on a disk of Pb via pulsed laser deposition. The central emitting area of Pb is masked by a shield to avoid the Nb deposition. The nanomechanical properties of the Nb film, obtained through nanoindentation measurements, reveal a hardness of 2.8±0.3 GPa, while the study of the electrical resistivity of the film shows the appearance of the superconducting transitions at 9.3 K and 7.3 K for Nb and Pb, respectively, very close to the bulk material values. Additionally, morphological, structural and contamination studies of Nb thin film expose a very low droplet density on the substrate surface, a small polycrystalline orientation of the films and a low contamination level. These results, together with the acceptable Pb quantum efficiency of 2×10−5 found at 266 nm, demonstrate the potentiality of the new concept photocathode. Funding agencies: Italian National Institute of Nuclear Physics (INFN); Italian MIUR through the Project FIRB Futuro in Ricerca [RBFR12NK5K]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]

The growth of Nb thin films on Si(100) substrates by pulsed Nd:YAG laser deposition (PLD) under different laser fluences (4–15 J/cm2) was reported. The influence of laser fluence on ablation rate and deposition rate was discussed. X-ray diffraction (XRD) investigations of the deposited films showed an amorphous structure. The droplet density on the film surface observed by scanning electron microscopy (SEM) analyses was extremely low. It was experimentally proved that the droplets on the film surface originated from liquid phase on the target surface. Profilometric measurements of the deposited Nb films revealed a substantial asymmetry in the film thickness related to the plume deflection effect. The measured electrical resistivity of the Nb film was higher than that of high purity Nb bulk. The present investigations of ablation and deposition process of Nb thin films are related to its potential application in superconducting radio-frequency (SRF) cavities.

Pb thin films were prepared by the nanosecond pulsed laser deposition technique on Si (100) and polycrystalline Nb substrates for photocathode application. As the photoemission performances of a cathode are strongly affected by its surface characteristics, the Pb films were grown at different substrate temperatures with the aim of modifying the morphology and structure of thin films. An evident morphological modification in the deposited films with the formation of spherical grains at higher temperatures has been observed. X-ray diffraction measurements showed that a preferred orientation of Pb (111) normal to the substrate was achieved at 30 °C while the Pb (200) plane became strongly pronounced with the increase in the substrate temperature. Finally, a Pb thin film deposited on Nb substrate at 30 °C and tested as the photocathode showed interesting results for the application of such a device in superconducting radio frequency guns.

Polyethylene oxide (PEO) films were grown by pulsed laser deposition using two different lasers: ArF (193 nm, 5 ns) and Nd:YAG (355 nm, 7 ns). Even though very similar experimental conditions have been applied to ablate identical targets, different surface morphologies and structures have been observed. Depending on laser fluence, labyrinthine patterns in PEO films have been formed when using 355 nm laser pulses at fluence values in the range 280–1000 mJ/cm2. The same material ablated by 193 nm excimer laser pulses at 200 mJ/cm2 fluence grows in dendritic morphologies. Both target and laser deposited materials have been thoroughly characterized using infrared spectroscopic, microscopic and X-ray analytical methods. Infrared spectroscopy demonstrated the close similarity of molecular chains for both target and film materials. X-ray diffraction analysis indicates polymer chain scissoring by ultraviolet irradiation, a fact also confirmed by size exclusion chromatography.

In this article we present and discuss the current status of thin film Pb photocathodes deposited by pulsed laser deposition (PLD) with different laser parameters, such as laser fluence, wavelength or pulse duration. The PLD technique appears very efficient for the fabrication of pure Pb photocathodes, providing good adherence and respectable quantum efficiency. The films deposited on the picosecond and subpicosecond regimes are practically free of big droplets and fragments, whereas in the nanosecond regime their presence cannot be neglected. All the films present a granular structure and polycrystalline character with preferential orientation along the (111) crystalline planes, irrespective of the laser pulse duration or wavelength. The main results obtained from the photoemission performance of Pb thin films deposited by PLD demonstrate their chemical stability under vacuum conditions and respectable quantum efficiency with a maximum of 7.3×10 −5 for films deposited on the subpicosecond regime. The photoemission properties confirm that Pb thin films deposited by PLD are a notable alternative for the fabrication of photocathodes for superconductive radio-frequency electron guns.

The authors study the nanomechanical and microtribological properties of yttrium (Y) thin films deposited by pulsed laser deposition on Cu polycrystalline substrates. Nanoindentation tests reveal that such films have a high hardness of H = 2.3 GPa and a reduced elastic modulus of 71.7 GPa with respect to the Cu substrates. The friction coefficient between a diamond tip and the Y film reaches a steady state value of μ ∼ 0.34, lower than that for the Cu (μ ∼ 0.38). Moreover, nanoscratch experiments show that Y films are more scratch-resistant than the Cu substrates, probably due to their greater hardness, higher elastic recovery, and lower friction coefficient. Their results confirm that the mechanical and tribological properties of the Y films are suitable for designing and fabricating scratch-resistant hybrid photocathodes and can reduce instabilities and unwanted discharges in the cavity of the radio-frequency gun. Furthermore, the low surface roughness and the low work function of the material are important characteristics for a photocathode based on the Y thin film for the production of high-brightness electron beams.

In this work yttrium and lead thin films have been deposited by pulsed laser deposition technique and characterized by ex situ different diagnostic methods. All the films were adherent to the substrates and revealed a polycrystalline structure. Y films were uniform with a very low roughness and droplet density, while Pb thin films were characterized by a grain morphology with a relatively high roughness and droplet density. Such metallic materials are studied because they are proposed as a good alternative to copper and niobium photocathodes which are generally used in radiofrequency and superconducting radiofrequency guns, respectively. The photoemission performances of the photocathodes based on Y and Pb thin films have been also studied and discussed. Funding agencies: Italian National Institute of Nuclear Physics (INFN); Italian Ministry of Research [RBFR12NK5 k]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]

In the last decade, UV-Excimer laser systems have been dramatically improved in terms of beam quality, power stability and gas lifetime. The benefits of using them for group IV semiconductor processing have, up to now, principally been recognized for some few processes like laser marking, UV-lithography and Excimer Laser Crystallization (ELC). Although several other techniques like Laser induced Chemical Vapor Deposition (LCVD), Excimer Laser Annealing (ELA) and Pulsed Laser Induced Epitaxy (PLIE) have been extensively studied 30 years ago for producing silicon coatings, little is known about the prospects of up-scaling those processes to other group IV semiconductors. This contribution presents UV-Laser processes combining LCVD of amorphous Si and of SiGeC alloys with their subsequent laser, in particular PLIE, treatment for modifying their composition and structure in order to engineer lattice parameters.

Research on epitaxial crystaline silicon (c-Si) and silicon-germanium (Si1-xGex) alloys growth and annealing for microelectronic purposes, such as Micro- or Nano-Electro-Mechanical Systems (MEMS or NEMS) and Silicon–On-Nothing (SON) devices is continuously in progress. Laser assisted annealing techniques using commercial ArF Excimer Laser sources are based on ultra-rapid heating and cooling cycles induced by the 193 nm pulses of 20 ns, which are absorbed in the near surface region of the heterostructures. During and after the absorption of these laser pulses, complex physical processes appear that strongly depend on sample structure and applied laser pulse energy densities. The control of the experimental parameters is therefore a key task for obtaining high quality alloys. The Finite ElementsMethod (FEM) is a powerful tool for the optimization of such treatments, because it provides the spatial and temporal temperature fields that are produced by the laser pulses. In this work, we have used a FEM commercial software, to predict the temperatures gradients induced by ArF excimer laser over a wide energy densities range, 0.1

A Finite Element Method (FEM) study of the coupled thermal-stress during the heteroepitaxial growth induced by excimer laser radiation of patterned amorphous hydrogenated silicon (a-Si:H) and germanium (a-Ge:H) bi-layers deposited on a Si(100) wafer is presented. The ArF (193 nm) excimer laser provides high energy densities during very short laser pulse (20 ns) provoking, at the same time, melting and solidification phenomena in the range of several tenths of nanoseconds. These phenomena play an important role during the growth of heteroepitaxial SiGe structures characterized by high Ge concentration buried under a Si rich surface. In addition, the thermal-stresses that appear before the melting and after the solidification processes can also affect to the epitaxial growth of high quality SiGe alloys in these patterned structures and, in consequence, it is necessary to predict their effects. The aim of this work is to estimate the energy threshold and the corresponding thermal-stresses in the interfaces and the borders of these patterned structures.

In this manuscript, a 3-D axisymmetric model for the heteroepitaxial growth induced by irradiating thin patterned amorphous hydrogenated silicon (a-Si:H) and germanium (a-Ge:H) bi-layers on Si (100) with pulsed UV-laser radiation, is presented. For reducing optimization steps, an efficient simulation of the laser induced processes that include rapid heating and solidification phenomena in the range of several tenth of nanoseconds, must be performed, if alloy composition and quality has to be adjusted. In this study, the effects of various laser energy densities on different amorphous Si/Ge bi-layer structures has been predicted and adjusted to obtain the desired Ge concentration profiles for applications as sacrificial layers, i.e. a Ge containing film buried under a Si rich surface layer. The numerical model includes the temperature dependent variations of the thermophysical properties and takes the coupled effects of temperature and hydrodynamic phenomena for a Boussinesq fluid, to estimate the element interdiffusion during the process and predicting the concentration profiles.

This manuscript presents a numerical analysis of the Excimer Laser Annealing and Crystallization induced in a set of amorphous hydrogenated silicon (a-Si:H) and germanium (a-Ge:H) bi-layers deposited on crystalline (c-) Si(100), with the aim to select the adequate range of energy densities for growing SiGe alloys of definite graded compositions, that might be useful as sacrificial layers for the fabrication of Si based Micro-Electro-Mechanical Systems and Silicon-On-Nothing devices. We have been able to predict the energy threshold to get an adequate epitaxial SiGe alloy growth with a thickness ranging from 10 to 30 nm. Temperature distribution, melting depth as well as the Ge concentration gradient have been calculated and compared with experimental results.

A combination of ArF-Excimer laser assisted techniques has been used for depositing and modifying ultra thin amorphous Si/Ge bi-layer structures. The first step consisted in producing, at low substrate temperatures, thin bi-layer coatings through Laser induced Chemical Vapour Deposition (LCVD) in both, large areas as well as in small regions of Si(1 0 0) wafers. In the second step, these bi-layer structures have been modified through Pulsed Laser Induced Epitaxy (PLIE) for obtaining heteroepitaxial SiGe alloys with a thin buried Ge rich layer, while keeping a shallow upper Si rich surface with good crystalline quality. Threshold for epitaxial alloy formation has been determined by Raman spectroscopy and estimated to be above 200 mJ/cm 2 . Optical profilometry has been used for evaluating the thickness of the structures and the lateral dimensions of patterned features. SEM, TOF-SIMS and XPS have been used to corroborate the results. For testing IC compatibility, some samples have been overgrown with epitaxial Si and etched through conventional IC processing techniques, revealing that the laser processed layers are suitable to be used as sacrificial layers for producing Micro-Electro-Mechanical Systems (MEMSs) or Silicon-on-Nothing (SON) devices.

The application of the striking electrical and optical properties of amorphous and nano-crystalline silicon in photovoltaic, photonic and nano-electronic devices is attracting increasing attention. In particular, its use both on polymeric substrates and in Integrated Circuit technology for the development of enhanced new devices has shown that processing techniques to produce amorphous hydrogenated and nano-crystalline silicon films avoiding high substrate temperatures are of great importance. A promising strategy to achieve this purpose is the combination of Hot-Wire Chemical Vapor Deposition at 150 °C with Excimer Laser Annealing, thus maintaining the substrate at relatively low temperature during the complete process. In this work we present a numerical analysis of Excimer Laser Annealing, performed at room temperature, of a multilayer structure of thin alternating a-Si:H and nc-Si films deposited on glass and grown by Hot-Wire Chemical Vapor Deposition. A set of two different layer thicknesses a-Si:H (25 nm)/nc-Si (100 nm) and a-Si:H (30 nm)/nc-Si (60 nm) were analysed for a total structure dimension of 900 nm. The aim is to determine the probable temperature profile to achieve controlled localized in depth dehydrogenation. Temperature distribution has been calculated inside the multilayer during the irradiation by a 193 nm Excimer laser, 20 ns pulse length, with energy densities ranging from 50 to 300 mJ/cm2. Calculations allowed us to estimate the dehydrogenation effect in the different layers as well as the structural modifications of the same layers as a function of the applied laser energy. The numerical results have been compared to the experimental ones obtained in similar multilayer structures that have been analysed through Raman spectroscopy and TOF-SIMS in depth profiling mode.

Ultraviolet (UV) Excimer laser assisted processing is an alternative strategy for producing patterned silicon germanium heterostructures. We numerically analyzed the effects caused by pulsed 193 Excimer laser radiation impinging on patterned amorphous hydrogenated silicon (a-Si:H) and germanium (a-Ge:H) bilayers deposited on a crystalline silicon substrate [Si(100)]. The proposed two dimensional axisymmetric numerical model allowed us to estimate the temperature and concentration gradients caused by the laser induced rapid melting and solidification processes. Energy density dependence of maximum melting depth and melting time evolution as well as three dimensional temperature and element distribution have been simulated and compared with experimentally obtained results.