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In this work laser-assisted methods for metal nanostructures formation and their application as active substrates in Surface Enhanced Raman Spectroscopy are presented. The nanostructures are fabricated by laser processing of gold thin films deposited on low cost substrates as glass, ceramic, polymer and paper. The films are deposited by classical PLD technology. The produced films are then processed by nanosecond pulses delivered by nanosecond Nd:YAG laser system. At certain conditions the laser treatment leads to formation of discrete nanostructure on the substrate surface. Femtosecond Pulsed Laser Deposition in air is also applied for direct deposition of gold nanostructure. In another set of experiments gold nanoparticle colloids are fabricated by laser ablation of gold target in chloroform. The fabricated structures are then tested as active systems in SERS, as detection of pesticides (DDT), nitrates (NH4NO3), and drugs (Methylene blue) is demonstrated. The obtained results show that these nanostructures can be efficiently used in the detection and monitoring of materials with a high social impact.

The composite nanostructures of double layer, multilayer and mosaic Ag/ZnO containing nano-sized particles have been produced by laser deposition and annealing procedures. The samples are investigated and the results indicated that laser annealing of Ag or Ag/ZnO layer is a feasible method to tune the optical properties of the nanostructures. Their morphology and optical absorption were investigated as a function of annealing regime and preparation procedure, leading to different silver arrangement. All annealed samples showed surface plasmon resonance (SPR) properties. The red shifted SPR was observed with the increase of the number of layers and is associated with the reduction of the interparticle distance. The absorption minimum of a mosaic samples broadens towards the longer wavelengths with reducing the thickness, due to the broader NPs size distribution. A ZnO excitonic feature visible in the spectra of double layer and multilayer structures disappear in the spectrum of a mosaic sample. The X-ray photoelectron spectroscopy was used to study the composition and chemical state of the double layer Ag/ZnO nanocomposites on the surface and in depth. The binding energy of Ag3d 5/2 shifts to the lower values compared to the pure metallic Ag due to the interaction between Ag and ZnO.

In this paper results on laser nanostructuring of Au/Ag and Au/Ni thin films are presented. The nanostructuring leads to formation of arrays of bimetallic nanoparticles. The fabrication of the these structures is made using a two step procedure. Initially, thin films are deposited on quartz substrates by classical pulsed laser deposition method. In order to produce Au/Ag or Au/Ni thin films, targets with two sections consist the different metals are used. Thin films with different concentrations of the two metals are obtained by changing the area of the different sections in the target. The as prepared films are then annealed by nanosecond laser pulses delivered by Nd:YAG laser system operated at λ = 355 nm. It is found that the laser annealing may lead to nanostructuring of the deposited films as at certain conditions decomposition into monolayers of nanoparticles with narrow size distribution is obtained. The performed EDX analyses indicate that the fabricated particles are composed by a bimetallic system of the basic metals used. The transmission spectra of the obtained structures show evidences of plasmon excitations. The bimetal nanostructures are covered with Rhodamine 6G and then tested as active substrates for Surface Enhanced Raman Spectroscopy (SERS).

Theoretical analysis on the electromagnetic field properties in vicinity of noble metal nanostructures is presented. The study is done on the basis of numerical simulation using Finite Difference Time Domain approach. The systems under consideration are two- and three-dimensional arrays composed of gold or silver nanoparticles. The near field intensity distribution and its enhancement are calculated for structures with different characteristics – particle size, inter-particle distance, and at different conditions related to the incident irradiation – polarization, and geometry of excitation. This analysis is used for definition of some optimal parameters for such structures from the viewpoint of application in Surface Enhancement Raman Spectroscopy (SERS). It is shown that the manipulation of the geometry of excitation of the nanoparticle system could be used as a crucial parameter for improving the efficiency of the classical configuration in SERS. The predicted influences of the nanoparticle system properties on the Raman signal enhancement are confirmed experimentally.

In this study, we synthesized different types of ZnO samples (thin and nanostructured films) and investigated their potential application in biomedicine. The properties of ZnO films are strongly dependent on the synthesis process and the experimental conditions. Thus, the samples were prepared by pulsed laser deposition (PLD), which allows excellent control over the stoichiometry and surface morphology. Cell suspensions of the same concentration and volume (i.e. same number of cells) were seeded on each sample. The subjects of interest were 3T3 fibroblast, MCF-7 and HeLa cancer cells. The influence of the ZnO surface morphology on the viability of these three different cell cultures was studied. The cell type defines the appropriate surface morphology for cell culturing. The nanoscale morphology of the samples supports the HeLa cell viability, while only a small quantity of MCF-7 cells are able to adhere, spread and survive on them.

Some basic features of ultrashort laser drilling of deep holes in Fe are investigated using molecular dynamics simulation model. The process is simulated for laser pulse duration of 0.1 ps at aspect ratio of the hole (hole depth/hole width) higher than 1. The interaction of the ablated material with the hole's wall affects its shape. The number of re-deposited, reflected, and secondary ejected particles from the walls is estimated as a function of the laser fluence. Significant secondary ejection of material from the walls is observed at fluences above 5 J/cm2.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Laser drilling of aluminum nitride (AIN) ceramics by 6 ns SHG (λ=532 nm) Nd:YAG laser pulses is studied. The drilling rate, quality of the holes, and the effects related to plasma formation are investigated. Numerical model based on the heat-transfer equation is developed to describe the drilling process. Different mechanisms of material decomposition are found to be realized, which depend on the laser fluence. They determine the quality of the holes produced. Below 5 GW/cm2 the material ejection is realized by decomposition of ceramics into solid or liquid Al and gaseous N2. The letter blows away culsters and flakes from the irradiated area and the holes drilled have irregular shape. At higher laser intensities, the decomposition into gaseous Al and N2 or direct evaporation of the ceramics results in good hole quality. A saturation of the ablation rate as a function of the laser intensity is observed above 15 GW/cm2. The calculated depths of the holes drilled are in agreement with the experimental data when absorption of the laser radiation from the plasma plume is taken into account.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Laser ablation of alumina (Al2O3), aluminum nitride (AIN) and silicon nitride (Si3N4) ceramics by 6 ns Nd:YAG laser operating at wavelengths of 1064 nm, 532 nm and 355 nm is studied. For all materials the maximum ablation rate is observed at wavelength 1064 nm, and the smallest one for irradiation at 532 nm in the case of Si3N4 and AIN. The numerical model, based on the heat-transfer equation describes the temperature distribution in the material and the evaporation process. The calculated depths of the drilled holes are in agreement with experiment.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Laser ablation of iron by femtosecond and picosecond pulses is investigated using molecular dynamics (MD). The electron heat conduction is taken into account in the simulations. Several stages of the ejection of the particles is determined. The compression and the subsequent relaxation of the pressure into the bulk lead to removal of large amount of the material. These processes are also accompanied with the formation of voids in the material. Two different regimes of the ablation are observed depending on the laser fluence. The estimated threshold of ablation is in good agreement with the experimental data found in the literature. The dynamics of the shock wave and the temperature distribution in the material are also obtained.

Samples of the 38HIMJ steel kept in a liquid nitrogen bath (LN2) at 77 K are treated by a 1 kW CO2 laser beam ofintensity of about 1.3 x iO W/cm2 on the sample surface. For thermal processing by means of the 10,6 pm radiation thetransparency window of LN2 below 0.3 eV is utilised. The irradiation effects are compared with results obtained for thereference samples of the same material under stanthrd gas shielding conditions. Measurements of microhardness HV 0.1 indicate on reduction of the heat affected zone for the LN2 case. A similar effect is observed for higher sample velocitiesand a value of about 700 HV is obtained in a 30 .tm surface layer. Surface analysis by means of Auger electron spectroscopyconfirms the local nitrogen enrichment ofthe laser treated areas depending on the processing conditions.Keywords: laser surface treatment, low temperature, microhardness, Auger electron spectroscopy, 38HMJ steel, nitriding 1. INFRODUCTION A growing need of efficient methods of the corrosion protection and modification of the steel surface structure stimulatesan extensive applied research and development of novel technologies. Among the well established processing methods suchas surface enrichment and nitriding the laser heat treatment at a presence of the chemically active environments becomesa powerful tool in numerous applications.