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Results concerning the controllable ablation of nano-layered thin films (NLTF) by femtosecond laser pulses are presented. Investigated samples were titanium-aluminum bilayers, deposited on a silicon substrate, with the top titanium or aluminum layer of variable thickness on the surface. Irradiation was done in ambient air with single femtosecond laser pulses under standard laboratory conditions. The samples were analyzed by complementary methods of optical and scanning electron microscopy and optical profilometry, exhibiting laser-fluence-dependent ablative removal either of the top layer or the entire bilayer or even partial ablation of the underlying silicon substrate. The removal (spallation) threshold fluences for the topmost layer are scalable versus its thickness almost irrespectively of its material, being rather selective for the Ti-coated samples and much less selective for the Al-coated samples. The removal of the entire bilayers was found to be strongly influenced by electronic properties of the underlying metallic layer, dictating the NLTF-Si adhesion, heat conduction, and capacity in the NLTFs toward the NLTF-Si interface and beyond, as well as by their thermophysical characteristics, e.g., almost twice higher melting temperature and enthalpy for Ti. As a result, precise fs-laser machining of the entire NLTFs is pronounced and selective for the samples with the fusible Al at the low-adhesion Al-Si interfaces, compared with the incomplete NLTF removal from the high-adhesion and refractory Ti-Si interfaces.

Modification of single and complex nickel-palladium samples by laser processing in the femtosecond time domain was studied. The samples were processed by focused Ti:Sapphire laser beam (Clark CPA-2101) with 775 nm laser wavelength, 2 kHz repetition rate, 200 fs pulse duration. The laser-induced morphological modifications have shown dependence on the applied fluences and number of laser pulses. The formed surface nanostructures on the single NiPd/Si and multilayer 5x(Ni/Pd)/Si systems are compared with individual Ni and Pd thin films. The results show an increase in surface roughness, formation of parallel periodic surface structures, appearance of hydrodynamic features and ablation of surface material. At low number of pulses (less than 10 pulses) and low pulse energies range (not over 1.7 mu J), the two types of laser-induced periodic surface structure (LIPSS) can be observed: low and high spatial frequency LIPSS (HSFL and LSFL). For all samples, the measured LSFL periods were 720 nm for the ripples created solely on thin film surfaces during the single pulse action. In the case of the multi-pulse irradiation, the periodicities of created LSFLs on the all investigated thin films have shown tendency to reduction with increasing of pulse energies. (C) 2016 Elsevier B.V. All rights reserved. 10th International Conference on Photo-Excited Processes and Applications (ICPEPA), Aug 29-Sep 02, 2016, Transilvania Univ Brasov, Brasov, Romania

Single-pulse microprocessing of a steel surface with a variable pulse width (0.3-12.3 ps) and a wavelength of 515 nm was performed. The morphology of the craters was visualized by a scanning electron microscope and an optical profilometer. The nonmonotonic behavior of ablation thresholds with a minimum at ≈1.5 ps, due to achieving the electron-phonon relaxation time of the absorbed energy in the steel was revealed. It is shown that, with an increase in the pulse width in the considered width range, the efficiency of the ablation decreases by a factor of 2, which is explained by the partial transition from the phase explosion to the surface evaporation. © 2019 Astro Ltd.

The dependences of the depth of single-pulse ablation of the steel surface on the energy density of ultrashort laser pulses (0.3–12 ps) with a wavelength of 515 nm have the form different from the usual logarithmic one for linear absorption of radiation. Since the density of states of free conduction electrons in the s band is low, and the d band of strongly bound electrons with a high density of states is located around the Fermi level, these dependences have been approximated within the two-photon absorption model. The two-photon absorption coefficient increases almost linearly with the duration of laser pulses, which indicates the saturation of absorption and allows estimating the corresponding parameters of the electronic subsystem. © 2019, Pleiades Publishing, Inc.

The oxidation behaviour and morphological modification of CrN/(Cr,V)N coatings on Si wafers were studied after UV nanosecond laser (wavelength 248 nm, pulse duration 25 ns) processing in ambient air. The evolution of the surface composition and microstructure with the number of accumulated/subsequent pulses was systematically analysed depending on the initial content of vanadium in the as-deposited coatings. Irradiation of CrN/(Cr,V)N coatings with different content of vanadium was carried out at a fluence of 0.17 J cm−2 with different number of pulses. The concentration of metallic components was fairly homogeneous distributed throughout the sample. However, on surface and in sub-surface regions the contents of Cr and V are diminished due to laser-induced oxidation. The composition and thickness of forming oxides mixture, Cr2O3 and V2O5, are depending on the number of applied laser pulses and the initial vanadium content. The asymmetric progress of surface morphology is characterized by the formation of grainy structures at peripheries and the appearance of cracks and irregular closed shapes in the centre of the irradiation area.

Single-shot femtosecond laser ablation of Ti(Al/Ti)(5) and (Ni/Ti)(5) films on silicon substrates was studied as a function of laser fluence by means of scanning electron microscopy, energy-dispersive x-ray spectroscopy, and optical profilometry. Ablation occurs as gradual threshold-like selective removal of a few top layers at lower fluences and rather continuous removal at higher fluences, exponentially increasing versus ablated depth, with the final complete (through) ablation of the entire films. The observed selective rupture at the different internal interfaces was related to thermomechanically and chemically enhanced (interface-facilitated) explosive boiling, with the corresponding energy deposition provided by cascaded heat transfer in the poorly conducting Ti and Ni, and highly conducting Al layers and the interfacial thermal (Kapitza) resistance effect. Published by AIP Publishing.

Processing of AlTiN/TiN multilayered hard coatings by femtosecond (fs) laser pulses has been investigated. Irradiation was performed in air with linearly polarized laser radiation with pulses of 200 fs duration at 775 nm wavelength. Single or 1000 subsequent laser pulses were directed at normal incidence towards target surface. Laser energy per pulse was adjusted from 0.5 to 50 µJ and corresponding fluence was 0.17–17.5 J cm−2. The as deposited and laser-ablated samples were characterized by optical confocal microscopy, optical profilometry and scanning and transmition electron microscopy. In case of the AlTiN/TiN coating, a single-pulse damage threshold of 0.41 J cm−2 was estimated. Well defined holes/craters with diameters from 7 to 35 µm, up to 40 µm depth were drilled, depending on laser pulse energy and number, after 1000 laser pulses. For small energy/fluence, laser induced periodical surface structures were observed. A model is discussed which can account for these features by the accumulation effect during multi-pulse irradiation. The forming craters can prove useful for fabrication of micron solid state lubricant reservoirs in the protective coating-steel system.

In this work we reported low and high repetition frequency femtosecond laser-induced modifications of tungsten-based thin film. The tungsten-titanium (WTi) thin film, thickness of 190 nm, was deposited by sputtering on single crystal Si (100) wafer. Irradiations were performed in air by linearly polarized and focused femtosecond laser beams with following parameters: (1) pulse duration 160 fs, wavelength 800 nm, laser repetition frequency (LRF) 75 MHz — high LRF, and (2) duration 40 fs, wavelength 800 nm, LRF of 1 kHz — low LRF. The results of femtosecond lasers processing of the WTi thin film revealed laser induced periodical surface structures (LIPSS) in the case of low LRF regime. LIPSSs were formed with different periodicity and different orientation to the laser polarization at the surface: micro-scale LIPSSs with orientation perpendicular to the laser polarization and nano-scale LIPSSs parallel and perpendicular to the laser polarization. After processing of the WTi/Si system in high LRF regime ablation and nano-particles formation were registered.

The surface oxidation of Ni/Ti bilayer, deposited on silicon substrate, affected by picosecond Nd: YAG laser radiation has been investigated. Fluence close to the target ablation threshold and multi-pulse laser irradiation regime were applied. Changes in the chemical composition of the formed surface oxide layer were studied by Elastic Recoil Detection Analysis (ERDA) and X-ray photoelectron spectroscopy (XPS). Morphological features analysis, at the oxide surface layer, was monitored, too. Laser modification as-deposited (Ni/Ti)/Si sample with 10 pulses induces a progressed interaction between Ni and Ti layers with the initial surface oxidation and formation of NiTi alloy phase. Progressed intermixing of components was achieved for the irradiation with 50 and more pulses, when all components were quite uniformly distributed to a depth of about 80 nm. An oxide layer was formed at the surface, with the specific combination of the oxide phases depending on the number of accumulated pulses. Changes in the morphological characteristics are reflected in the increase of the mean surface roughness and the generation of a certain number of cavities. These features are decreased with increasing number of pulses, caused by the surface melting and a pronounced mobility of the materials. (C) 2013 Elsevier B.V. All rights reserved.

Laser-induced alloying effects on the composition and structure of different Ni/Ti multilayer structures were studied. Thin films composed of one, five, and ten (Ni/Ti) bilayers were deposited by DC ion sputtering on (1 0 0) Si wafers. Laser irradiations were performed by 150 ps pulses of a Nd:YAG laser operating at 1064 nm. The samples were characterized by Rutherford backscattering spectrometry (RBS), Auger electron spectroscopy (AES), X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). At a laser fluence of 0.9 J cm(-2), interaction between Ni and Ti layers was initiated, and NiTi alloy formed in 5- and 10-bilayered samples. Progressed alloying was achieved at a laser fluence of 1.2 J cm(-2). The alloy was formed mostly within the heat affected zone (HAZ) of the sample. Surface segregation of titanium was followed by formation of a 25 nm thin TiO2 film on the surface of the multilayered structures. In addition, parallel periodic surface structures on the surfaces of the 5- and 10-bilayered samples were clearly recorded. Their period in the case of the 5-bilayered system (0.77 mu m) agrees very well with the predictions of the common theory, whereas, in the case of the 10-bilayered system, two periods of such structures are observed (1.43 mu m and 0.4 mu m), and none of them coincides with the prediction. (C) 2012 Elsevier B. V. All rights reserved.

The response of titanium surface irradiated with high intensity (1013 – 1015 W/cm2) Ti:sapphire laser was studied in vacuum. Most of the reported investigations were conducted with nano- to femtosecond lasers in gas atmospheres while the studies of titanium surface interacting with femtosecond laser in vacuum are scarce. The laser employed in our experiment was operating at 800 nm wavelength and pulse duration of 60 fs in single pulse regime. The observed surface changes and phenomena are (1) creation of craters, (2) formation of periodic surface structures at the reduced intensity, and (3) occurrence of plasma in front the target. Since microstructuring of titanium is very interesting in many areas (industry, medicine), it can be concluded from this study that the reported laser intensities can effectively be applied for micromachining of the titanium surface (increasing the roughness, formation of parallel periodic surface structures etc.).

Interaction of a Nd:YAG laser, operating at 1064 nm wavelength and pulse duration of 150 ps, with Ni/Ti multilayer thin films was studied. Nanocomposite structure of five (Ni/Ti) bilayers deposited by DC ion sputtering on Si(100) wafers to a total thickness of ca. 180 nm was treated with a laser pulse energy of about 55 mJ without focusing (fluence 1 J cm(-2)), Multi-pulse laser irradiation was done at an incidence angle of 22 degrees in air. The composition and surface morphology were monitored by Auger electron spectroscopy (AES), scanning electron microscopy (SEM), and by atomic force microscopy (AFM). The main part of the absorbed laser energy was rapidly transformed into heat, producing intensive modifications of composition and morphology on the target surface. Besides surface oxidation, the results show an increase in surface roughness, formation of a regularly rippled surface topography and microcracking. Depth profile AES analysis revealed that laser annealing induced intermixing between the components of individual Ni and Ti layers with indications of possible formation of NiTi intermetallic compounds. An interesting finding is the surface segregation of Ti, although the top layer was Ni, prior to laser irradiation. (C) 2011 Elsevier B.V. All rights reserved. Symposium K on Protective Coatings and Thin Films held at the European-Materials-Research-Society Spring Meeting (E-MRS), May 09-13, 2011, Nice, France

We studied surface modification of a double layer protective coating on steel induced by single fs laser pulse irradiation in ambient air. The outer alumina (Al2O3) layer, which protects against aggressive environments, was 1.7 mu m thick and the titanium aluminum nitride (TiAlN) layer in contact with the steel surface had a thickness of 1.9 mu m. The pulses (lambda=775 nm, tau=200 fs) were generated by a Ti:sapphire laser source. The pulse energy was varied from 0.32 mu J to 50 mu J, corresponding to an incident laser fluence of 0.11 J cm(-2) to 16.47 J cm(-2). The surface damage threshold was found to be 0.20 J cm(-2) and the alumina layer removal was initiated at 0.56 J cm(-2). This selective ablation of alumina was possible in a wide range of fluences, up to the maximum applied, without ablating the TiAlN layer beneath. (C) 2012 Elsevier B.V. All rights reserved.

In this work we studied the influence of laser radiation on the composition, structure and morphology of WTi thin films deposited on n-type (100) silicon wafers. The films were deposited by d.c. sputtering from a 70:30 at% W-Ti target, using Ar ions, to a thickness of similar to 190 nm. Irradiation was performed with a pulsed Nd:YAG laser operating at 1064 nm, whereas the pulse duration was 150 ps. Laser fluences of 3.2 and 5.9 J/cm(2) were found to be sufficient for modification of the WTi/silicon target system. The results show: (i) ablation of WTi thin film and a Si substrate in the central zone of spots, (ii) appearance of hydrodynamic features like resolidified material, (iii) partial ablation of the WTi thin film at the periphery and (iv) appearance of thin film cracks at the far periphery. On the non-ablated areas, the laser modification induced changes in composition, such as inter-mixing of components at the WTi/Si interface with formation of silicides in both metals. Surface oxidation was the dominant process in the ablated areas, which is demonstrated by the presence of a SiO2 phase.

Surface texturing of the metals, including steels, gained a new dimension with the appearance of femtosecond lasers. These laser systems enable highly precise modifications, which are very important for numerous applications of metals. The effects of a Ti:sapphire femtosecond laser with the pulse duration of 160 fs, operating at 775 nm wavelength and in two operational regimes - single pulse (SP) and scanning regime, on a high quality AISI 1045 carbon steel were studied. The estimated surface damage threshold was 0.22 J/cm(2) (SP). Surface modification was studied for the laser fluences of 0.66, 1.48 and 2.37 J/cm(2). The fluence of 0.66 J/cm(2), in both working regimes, induced texturing of the material, i.e. formation of periodic surface structures (PSS). Their periodicity was in accordance with the used laser wavelength. Finally, changes in the surface oxygen content caused by ultrashort laser pulses were recorded. (C) 2011 Elsevier B.V. All rights reserved.

In this work we have studied the influence of laser modification on the composition and structure of tungsten titanium (WTi) thin films, deposited on n-type (100) silicon wafers. After deposition, the samples were multi-pulse laser irradiated in a nitrogen, oxygen, and helium ambient. The composition of the WTi/Si sample was determined by Elastic Recoil Detection Analysis (ERDA). Surface morphology was monitored by Atomic Force Microscopy (AFM). In the experiment, typical laser output parameters were: wavelength 1064 nm, pulse duration 150 ps, and laser pulse energy 30 mJ. Surface concentrations of W and Ti, as well as the concentration of gas components nitrogen and oxygen were determinated before and after the action of laser radiation in different ambient conditions. The contents of W and Ti decreased after irradiation due to adsorbed gases from the surrounding atmosphere. After surface irradiation in the inert ambient (He), the concentrations of the components were not significantly changed. In other cases, oxygen was the dominant component at the surface, probably due to the high affinity of thin film components. Also, the morphological changes occurred at the surface of WTi, as an increase in the surface roughness and formation of the granular structures are a result of laser-induced surface oxidation and recrystallization. International Conference on Advanced Laser Technologies (ALT10), Sep 11-16, 2010, Egmond aan Zee, Netherlands

In this work we have studied the influence of thermal annealing on the structural and electrical properties of W-Ti thin films, deposited on n-type (100) silicon wafers. The films were deposited by d.c. sputtering from a 90:10 wt.%W-Ti target, using Ar ions, to a thickness of similar to 170 nm. After deposition the samples were annealed at 400 to 700 degrees C for 60 min, in a nitrogen ambient. Structural characterizations were performed by X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). A four-point probe was used for electrical characterization. It was found that the as-deposited films exhibit a polycrystalline structure in the form of columnar grains (2050 nm in diameter). Only b.c.c. W phase could be registered in the films, while any presence of crystalline Ti was hindered in XRD and electron diffraction patterns. Annealing at up to 600 degrees C resulted in an increase of the mean grain size in the films, and a decrease of their sheet resistance. For these annealing temperatures we did not register any interaction at the W-Ti/Si interface. However. upon annealing at 700 degrees C, a progressed interaction between the film and the substrate occurred. Structural analyses suggest the formation of both W and Ti silicides. The estimated thickness of the formed metal-silicide layer is approximately 125 nm. Sheet resistance increased rapidly after annealing at 700 degrees C, because a large portion of the original metallic film was consumed in the reaction with silicon. (C) 2009 Elsevier B.V. All rights reserved. Symposium on Protective Coatings and Thin Films held at the 2009 E-MRS Spring Meeting, Jun 08-12, 2009, Strasbourg, France

The effects of ultra-short laser pulses on reactive Ti/Al nano-layered thin film were investigated. The thin film composed of alternated titanium and aluminium nano-layers, was deposited by ion-sputtering. Single pulse irradiation was conducted in the air with focused and linearly polarized femtosecond laser beam - of 1026 nm wavelength and pulse duration of 170 fs. Laser induced composition and morphological changes, using different microscopy techniques and energy dispersive X-ray spectroscopy, were investigated. Following results were obtained: (i) one step partial/selective ablation of upper Ti layer from nano-layer Ti/Al at low laser fluence and (ii) two step ablation or entire ablation of nano-layer Ti/Al at higher laser fluence. Single pulse selective ablation of the upper Ti layer was confirmed based on profiling (AFM) along the ablation steps and reduction of Ti concentration (EDX) in the ablated areas. Ablation threshold was estimated using well known procedure for ultra-short laser pulses - spot diameter square versus logarithm of pulse energy. To interpret the experimental observations, simulations have been performed to explore the thermal response of the multiple layered structure (Ti(5x(Al/Ti))) after irradiation with a characteristic value of single laser pulse of fluence F = 320 mJ/cm2. The results are in agreement with the calculations.

Interaction of a Nd:YAG laser, operating at wavelengths of 1064 nm (23.6 J cm−2 fluence) or 532 nm (25.9 J cm−2 fluence), and pulse duration of 40 ps, with a titanium-based medical implant Ti6Al4V alloy was studied. Surface damage thresholds were estimated to be 0.9 J cm−2 and 0.25 J cm−2 at laser wavelengths 1064 nm and 532 nm, respectively. At both laser wavelengths, the energy absorbed was mostly converted into thermal energy, forming craters, albeit about 50 times deeper at 1064 nm than at 532 nm. Periodic surface structures (PSS) were also formed with both laser wavelengths, concentric, and radial at micrometer scale (3 µm to 15 µm period), parallel at nanometer scale (800 nm period with the 1064 nm laser, 400 nm with the 532 nm laser). In the case of the 532 nm laser, the concentric structures enlarge their period with accumulating laser pulse count. These features can help roughening of the implant surface and improve bio-compatibility.

Creation of laser-induced morphology features, particularly laser-induced periodic surface structures (LIPSS), by a 532 nm picosecond Nd:YAG laser on crystalline silicon is reported. The LIPSS, often termed ripples,. were produced at average laser irradiation fluences of 0.7, 1.6, and 7.9 J cm(-2). Two types of ripples were registered: micro-ripples (at micrometer scale) in the form of straight parallel lines extending over the entire irradiated spot, and nano-ripples (at nanometer scale), apparently concentric, registered only at the rim of the spot, with the periodicity dependent on laser fluence. There are indications that the parallel ripples are a consequence of the partial periodicity contained in the diffraction modulated laser beam, and the nano-ripples are very likely frozen capillary waves. The damage threshold fluence, was estimated at 0.6 J cm(-2). (c) 2007 Elsevier B.V. All rights reserved.

The W-Ti thin films are deposited by the dc Ar+ sputtering of W(70%)-Ti(30%) a.t. target on silicon substrates. The surface composition and structure of the thin film, previously exposed to air, was carded out. The surface structure was undertaken using grazing incidence X-ray diffraction (GIXRD), and compared to that of the thin film interior. The surface morphology was determined by the Scanning Tunneling Microscopy (STM). The surface composition and chemical bonding of elements on the Ti-W film were analyzed by X-ray photoelectron spectroscopy (XPS) and Low Energy Ion Scattering (LEIS). The measurements show that the overlayer of metallic oxides TiO2, and WO3 is formed. The first atomic layer is occupied by TiO2 only, and its thickness is estimated to about 3.2 +/- 0.4 nm. The strong surface segregation of Ti is triggered by the surface oxidation, which is confirmed by the thermodynamical considerations. (c) 2007 Elsevier B.V All rights reserved.

The effects of UV femtosecond laser beam with 76 MHz repetition rate on two types of thin films on Si substrate - the Al single layer thin film, and the multilayered thin film consisted of five Al/Ti bilayers (total thickness 130 nm) - were studied. The surface modification of the target was done by low fluences and different irradiation times, not exceeding similar to 300s. Nanopatterns in the form of femtosecond-laser induced periodic surface structures (fs-LIPSS) with periodicity of LT 315 nm and height of 45 nm were registered upon irradiation of the thin films. It was shown that: (i) the fs-LIPSS evolve from ruffles similar to high spatial frequency LIPSS (HSFL) into a low spatial frequency LIPSS (LSFL) if a certain threshold of the fluence is met, (ii) the number of LSFL increases with the exposition time and (iii) the LSFL remain stable even after long exposure times. We achieved high-quality highly-controllable fabrication of periodic structures on the surface of nanosized multilayer films with high-repetition-rate low-fluence femtosecond laser pulses. Compared to the Al single layer, the presence of the Ti underlayer in the Al/Ti multilayer thin film enabled more efficient heat transmittance through the Al/Ti interface away from the interaction zone which caused the reduction of the ablation effects leading to the formation of more regular LIPSS. The different outcomes of interactions with multi and single layer thin films lead to the conclusion that the behavior of the LIPSS is due to thin film structure. (C) 2014 Elsevier B.V. All rights reserved.

In this work we investigated the interaction of ns laser pulses (TEA CO2 and Nd:YAG) with a titanium nitride (TiN) thin film. The TiN thin film of 1μm thickness was deposited by PVD method on silicon substrate. Modification of TiN film was induced by laser pulses with power densities of about 108 and 109 W/cm2. Part of the laser energy absorbed on the target surface was converted into thermal energy and effects such as melting, vaporization and exfoliation were observed. Nd:YAG laser produced craters with sharp periphery, while TEA CO2 laser created damages with broad boundary zone. Hydrodynamic effects were especially pronounced during irradiation with TEA CO2 laser.

The effects of an Nd:YAG laser interaction with titanium target using laser radiation at wavelengths 1.064 or 0.532 mu m (40 picoseconds pulse duration) were studied. Modification of target surfaces at laser energy densities of 2.4 and 10.3 J/cm(2) (lambda(laser)(1) = 1.064 mu m) and 1.1 J/cm(2) (lambda(laser)(2) = 0.532 mu m) are reported in this article. Qualitatively, the titanium surface modification can be summarized as follows: (i) ablation of the titanium surface in the central zone of the irradiated area for both laser wavelengths; (ii) appearance of a hydrodynamic feature like resolidified droplets of the material (lambda(laser)(1) 1.064 mu m), as well as formation of the wave-like microstructures (lambda(laser)(2) = 0.532 mu m); and (iii) appearance of plasma, in front of the target, with both laser wavelengths. Recent Developments in Advanced Materials and Processes, 7th Conference of the Yugoslav-Materials-Research-Society (Yu-MRS), Sep 12-16, 2005, Herceg Novi, Montenegro

Interaction of a transversely excited atmospheric (TEA) CO2 and excimer-KrCl laser, pulse duration similar to2 mus (FWHM of initial spike similar to100 ns) and similar to12 ns (FWHM), respectively, with polycrystalline titanium nitride (TiN) coating deposited on high quality steels, was studied. The results have shown that the titanium nitride was surface modified by the laser beam, with an energy density (ED) of 43.0 J/cm(2) (TEA CO2 laser system) and 3.3 J/cm(2) (KrCl system), respectively. The energy absorbed from the CO2 laser beam is partially converted to thermal energy, which generates a series of effects such as melting, vaporization of the molten material, shock waves, etc. The energy from the excimer-KrCl laser primarily leads to a fast and intense target evaporation. Calculated maximal temperatures, on the target surface, were 3940 and 8000 K for the TEA CO2 and the KrCl lasers, respectively. It is assumed that TEA CO2 laser,affects, the target deeper, during a longer time than the KrCl laser. The effects of the KrCl laser are confined to a localized area, near target surface, in the course of short time. The following morphological changes of titanium nitride surface were observed: (i) both types of laser caused ablation of the TiN coating in the central zone of the irradiated area, (ii) appearance of a hydrodynamic feature like resolidified droplets of material in the surrounding outer zone (cracking) in the case of the TEA CO2 laser, and (iii) appearance of wave-like microstructures (consisting of periodic parallel fringes with a period of about 20 microns) in the case of KrCl laser. Formation of the wave-like microstructures is discussed in the context of laser-induced periodic surface structure (LIPSS) effects and diffraction phenomena. The process of the CO2 and KrCl laser interaction with titanium nitride were typically accompanied by plasma formation. Plasma appeared above the target after about 40 and 1 laser pulse, respectively. (C) 2003 Elsevier B.V. All rights reserved.

The interaction of a transversely excited atmospheric (TEA) CO, laser, pulse duration of about 2 mus (FWHM of initial spike = 120 ns), with p-type single crystalline silicon doped by boron, was studied. The results have shown that the silicon was surface modified by the laser beam of 12.0 J cm(-2) energy density. The energy absorbed from the CO, laser beam is converted partially into thermal energy, which generates a series of effects such as melting, vaporisation of molten material, shock waves, etc. Morphological manifestations on the silicon surface are: nonuniform modifications (central zone of interaction); wave-like periodical microstructure (inner periphery zone); hydrodynamical structure-like droplets (outer periphery zone). Wave-like microstructure consists of periodic parallel fringes with a period of about 0.8 mum. Formation of these wave-like microstructures is very complex. Explanation includes a consideration of the laser-induced periodic surface structure (LIPSS) effect. The process of the CO2 laser interaction with silicon was not initially accompanied by plasma. Plasma, in the form of a spark, typically appeared after about 100 cumulated laser pulses. (C) 2002 Elsevier Science B.V. All rights reserved.

Results of laser-induced oxidation (100−500 Hz frequency, 1064 nm wavelength, and 1 ns pulse duration) and formation of micro- and nanostructures on the surface of high-quality structural carbon steel (0.42 wt.% C, 0.5 wt.% Mn, 0.25 wt.% Cr) are presented. The steel samples were irradiated in ambient air, water, 3% hydrogen peroxide, and ethanol by a series of laser pulses at a power density of (3.2−4.4)·109 W/cm2, which is close to the ablation threshold. The surface structures were examined by optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy. Different kinds of structures detected on the steel surface and the efficiency of oxide formation depend strongly on both the liquid or gaseous environments and the parameters of laser treatment. It was found that the efficiency of nano/microstructures and oxides formation on structural steel is especially expressed for samples irradiated in air and hydrogen peroxide environments.

The conditions of ultra-thin oxide films synthesized as the Al/Fe multilayer structures after the surface treatment with femtosecond laser radiation were studied. Thin films composed of three (Al/Fe) bilayers were deposited by DC ion sputtering on (100) Si wafers to the total thickness of 410 nm. Laser irradiations were performed by 40-fs pulses of a Ti:Sapphire laser operating at 800 nm, at fluences slightly higher than the ablation threshold. The samples were characterized by Auger electron spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. Progressed intermixing of components was achieved for the irradiation with fluence of 0.43 J cm(-2), when intermetallic phase was formed and all components were almost uniformly distributed through the entire multilayer structure. Exception is the subsurface region, to the thickness of 20 nm, where the distribution of constructive components and their oxide is changing with the distance from the surface, and this distribution depends on the applied laser fluences. An ultra-thin oxide layer was formed at the surface, with the specific combination of the oxide phases, Al2O3 and Fe2O3, depending on the applied fluences. Laser-induced modification was accompanied with the ablation of the material and the creation of parallel periodic structures. These effects of laser-induced morphological features are increased with increasing laser fluences, caused by the pronounced mobility of the materials. The special morphology of the laser-assisted synthesis of mixture of Al2O3 and Fe2O3 in the form of an ultra-thin oxide layer can improve their characteristics for functional applications, as catalysts and sensors.

Results of surface modification are presented for MnNiCrMo-steel samples exposed to a Nd:YAG laser operating in a pulse-periodic mode (10 Hz frequency, 532 nm wavelength and 17 ns pulse duration). The steel samples were irradiated in air by a series of laser pulses at a fluence of 10.7 J cm(-2) close to a plasma formation threshold. Surface structures were examined by optical, scanning electron and confocal optical microscopy. The appearance of the detected surface structures strongly depends on the number of laser pulses and power density of laser radiation. Significant differences were found between laser-induced structures in the center of the laser spot, at its edges and in the nearest surrounding of the laser spot. The reasons for such differences are discussed. 4th International School and Conference on Photonics, Aug 26-30, 2013, Belgrade, Serbia

In this work, the interaction of a transversely excited atmospheric (TEA) CO2 laser with tungsten–titanium (W-Ti) alloy deposited on austenitic stainless steel is considered. The W-Ti alloy as a refractory material possesses very good physicochemical characteristics such as thermochemical stability and high melting temperature. Studying of interactions of different energetic particles or laser beams with W-Ti coatings has both application and fundamental importance.The morphological features of the W-Ti coating, deposited on austenitic stainless steel AISI 316, induced by a TEA CO2 laser after multipulse cumulative laser action, have been considered. The laser pulses with tail (FWHM = 120 ns, tail = 2 μs) and free-tail pulses (FWHM = 80 ns) have been employed. Laser pulses used in the experiment had equal peak power density I = 120 MWcm−2. For the given peak power density, excessive surface changes on the coating were registered. From direct observation on a microscopic scale (OM, SEM), it can be concluded that W-Ti coatings show different behavior under laser irradiation with various temporal pulse shapes.

In this work the changes induced by TEA CO laser with different pulse shape on low thickness TiN coatings were considered. The TiN layer (0.85 mu m) was deposited by sputtering. The bombardment of coatings was performed in the air with TEA CO2 laser operating in multimode regime with energies 7.5-78.3 J/cm(2). The coating properties and laser induced damage after 20 pulses (threshold) and 340 pulses were analyzed by SERI and EDAX. The results have shown that the beams induced changes to form an alloy layer with a specific composition. It was shown that the morphological features and damage induced during the interaction depend on the intensity and the pulse shape. The bombarded area consists of three zones. The central zone is more pronounced with tail free pulses. (C) 1999 Elsevier Science S.A. All rights reserved. 14th International Vacuum Congress/10th International Conference on Solid Surfaces/5th International Conference on Nanometre-Scale Science and Technology/10th International Conference on Quantitative Surface Analysis, Aug 31-Sep 04, 1998, Birmingham, England

When an energy-carrying beam strikes a solid surface, the surface is sputtered and many effects on the atomic, microscopic and macroscopic scale can be observed. The morphological changes induced on solid surfaces, the shape and size of damaged area depend on the beam and target characteristics. Laser beams are frequently used in modem technology to obtain materials with certain bulk properties and different surface properties. During the last years, then has been an interest for advanced technology application of implemented ceramic thin films/coatings deposited by various methods. In this work the microscopic changes induced by laser beam on TiN and (Ti,Al)N coatings deposited on steel were studied, For this purpose we used pulsed, Transversely Excited Atmospheric (TEA) CO2 laser, operating with typical and non-typical gas mixtures. The deposited coatings and laser-induced damage after 20-340 pulses were analyzed by X-ray, optical and scanning electron microscopy (SEM). It was shown that the morphological features and damages induced during the laser irradiation depend on the pulse shape, total deposited energy and type of targets. From direct observation on microscopic scale, it can be concluded that similar coatings TiN and (Ti,Al)N showed different behaviour under pulsed laser irradiation. (C) 1999 Elsevier Science B.V. All rights reserved.

This work reports on an analysis of titanium nitride layers deposited by the PVD method and changes induced in the deposit during interaction with a laser beam. Layers up to 850 nm thick were deposited by Ti target sputtering into an atmosphere of reactive gas. Layer phase composition, lattice parameter, interplanar spacing and preferential orientation of crystallites in the layer were investigated by X-ray diffraction analysis. The mean grain size and micro strain in the deposit were defined from peak line broadening in the CuK alpha spectrum. Crystallite size was defined additionally by scanning tunnelling microscopy (STM), before and after laser beam treatment.

The interaction of an Er, Yb, Cr-glass laser, operating at 1540 nm wavelength and a pulse duration of 40 ns, with Ni/Ti multilayer thin films has been studied. Five (Ni/Ti) bilayers deposited by DC ion sputtering on Si(100) wafers to a total thickness of about 180 nm were treated with laser fluences of about 6.4 and 8.8 J cm(-2). Single and multi-pulse laser irradiation was done at normal incidence in air, water and ethanol ambients. The composition and surface morphology were monitored by particle-induced x-ray emission, Rutherford backscattering spectrometry (RBS), scanning electron microscopy and profilometry. Most of the absorbed laser energy was rapidly transformed into heat, producing intensive modifications of composition and morphology on the target surface. The results show an increase in surface roughness, formation of parallel periodic surface structures, appearance of hydrodynamic features and ablation of surface material. RBS analysis revealed that laser modification induced inter-mixing between the components of individual Ni and Ti layers, with indications of the formation of NiTi intermetallic compounds. An interesting finding is the morphological changes dominant in the Si substrate, whereas the Ni/Ti multilayer structure has mainly undergone changes in the chemical composition.

A study of morphological and composition changes of the (8(Al/Ti)/Si) system induced by laser pulses in different ambient conditions is presented. The effects of an Er, Yb, Cr-Glass laser, operating at 1540 nm wavelength with pulse duration of 44 ns, on a complex target were investigated. Irradiation of 8(Al/Ti)/Si was carried out at intensities of 5.9 and 9.5 x 10(11) W m(-2) in air, water and ethanol. The laser-induced morphological and composition modifications have shown dependence on applied intensities, number of laser pulses and ambient conditions. The following morphological changes were observed: (i) intense surface melting of the thin film and Si-substrate; (ii) ablation/exfoliation of the 8(Al/Ti) multilayer thin film from Si, (iii) appearance of hydrodynamic features such as resolidified material, and (iv) formation of crater at multi-pulse action. The formation of parallel periodic surface structure was only occurring in single pulse air-assisted modification. Analysis of the composition revealed that laser modification induced intermixing between the components of individual Al and Ti layers with potential formation of AlTi intermetallic compounds. (C) 2013 Elsevier Ltd. All rights reserved.

Laser-induced periodic surface structures (LIPSSs) and chemical composition changes of Ti-based nanolayered thin films (Al/Ti, Ni/Ti) after femtosecond (fs) laser pulses action were studied. Irradiation is performed using linearly polarized Ti:Sapphire fs laser pulses of 40 fs pulse duration and 800 nm wavelength. The low spatial frequency LIPSS (LSFL), oriented perpendicular to the laser polarization with periods slightly lower than the irradiation wavelength, was typically formed at elevated laser fluences. On the contrary, high spatial frequency LIPSS (HSFL) with uniform period of 155 nm, parallel to the laser light polarization, appeared at low laser fluences, as well as in the wings of the Gaussian laser beam distribution for higher used fluence. LSFL formation was associated with the material ablation process and accompanied by the intense formation of nanoparticles, especially in the Ni/Ti system. The composition changes at the surface of both multilayer systems in the LSFL area indicated the intermixing between layers and the substrate. Concentration and distribution of all constitutive elements in the irradiated area with formed HSFLs were almost unchanged. (C) 2013 AIP Publishing LLC.

The interaction of a transversely excited atmospheric (TEA) CO2 laser with chromium oxynitride (CrON) coating deposited on a AISI 304 steel substrate was considered. The results have shown that CrON was surface-modified by the laser beam of 45 J/cm(2) energy density. The energy absorbed from the TEA CO2 laser beam was partially converted into thermal energy, which has generated a series of effects such as melting, vaporization of the molten material, and shock waves in the vapor and in the solid. Morphological manifestations on the CrON coating surface can be summarized as follows: non-uniform features with ablation and appearance of crater-like form (central zone of interaction); appearance of three damaged areas and presence of hydrodynamic effects with resolidified droplets (periphery zone of interaction). In case of applied energy density the interaction of laser radiation with CrON has been always followed by plasma creation in front of the coating.

Ion implantation and thermal annealing effects on composition and structure of Ni/Ti multilayer have been studied and reported in this paper. The thin films composed of five (Ni/Ti) bilayers were deposited by d.c. ion sputtering on (100) Si wafers to a total thickness of similar to 180 nm. Ion irradiations were performed by 180 keV Ar+ ions with fluence of 6 x 10(16) ions cm(-2). After deposition and implantation, the samples were annealed at 400 degrees C for 30 min in an inert ambient. Composition and structural characterizations were performed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Annealing of as-deposited samples at 400 degrees C induces a progressed interaction between Ni and Ti layers with the initial formation of NiTi alloy phase. Progressed alloying was achieved for the ion fluence of 6 x 10(16) ions cm(-2) and the formed structure is composed of NiTi compound, only at depth around the projected ion range. In the deeper layers, beyond the projected range of implanted ions, the diffusion of Ni atoms can lead to solid state amorphization. Subsequent annealing at 400 degrees C for 30 min enabled enhanced interaction between intermixed Ni and Ti layers, and in the layers close to the Si substrate the conditions for the formation of intermetallic compound are created. (c) 2012 Elsevier Ltd. All rights reserved.

A comparative study of superficial changes on the superalloy Inconel 600, induced by a picosecond Nd:YAG laseroperating at 1064, 532, and 266 nm, is presented. All of the laser wavelengths, as well as the used fluences of 2.5(1064 nm), 4.3 (532 nm), and 0.6 J/cm 2 (266 nm) were found to be adequate for inducing surface variations. Quitedifferent surface features were produced depending on the laser wavelength used. The measured surface damagethresholds were 0.25, 0.13 and 0.10 J/cm 2 for 1064, 532, and 266 nm, respectively. Drastic differences, in function ofthe wavelength used, were recorded for the crater depths, as well the appearance of hydrodynamic effects and periodicsurface structures. Differences in crater depths were explained via an easier propagation of the first harmonic laserradiation (1064 nm) through the ejected material and plasma compared to a radiation at 532 and 266 nm. Finally,changes in the surface oxygen content caused by ultrashort laser pulses were considered.Keywords: Laser ablation; Periodic surface structures; superalloy Inconel; Surface morphology

Interaction of a TEA CO2 laser, operating at 10.6 mu m wavelength and pulse duration of 100 ns (FWHM), with a titanium implant in various gas atmospheres was studied. The Ti implant surface modification was typically studied at the moderate laser beam energy density/fluence of 28 J/cm(2) in the surrounding of air, N-2, O-2 or He. The energy absorbed from the TEA CO2 laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following titanium implant surface changes and phenomena were observed, depending on the gas used: (i) creation of cone-like surface structures in the atmospheres of air, N-2 and O-2, and dominant micro-holes/pores in He ambient; (ii) hydrodynamic features, most prominent in air; (iii) formation of titanium nitride and titanium oxide layers, and (iv) occurrence of plasma in front of the implant. It can be concluded from this study that the reported laser fluence and gas ambiences can effectively be applied for enhancing the titanium implant roughness and creation of titanium oxides and nitrides on the strictly localized surface area. The appearance of plasma in front of the implants indicates relatively high temperatures created above the surface. This offers a sterilizing effect, facilitating contaminant-free conditions. (C) 2011 Elsevier B.V. All rights reserved.

A target of multilayered TiAlN/TiN coating deposited on steel was irradiated by 200 fs pulses of a Ti:Sapphire laser, operating at 775 nm. Laser fluences of 1.16 J cm(-2) to 116 J cm(-2) produced a range of modifications, from well defined parallel surface structures on the coating, to deep craters in the substrate. Parameters for coating ablation were determined in terms of laser fluence and pulse count. A single-pulse damage threshold was found to be 0.66 J cm(-2) and the damage incubation factor 0.642. At lower laser fluences formation of laser induced parallel surface structures was evident, beginning from the first pulse, with a periodicity of about 580 nm. These structures remained and were pronounced at the rim of the damage spot even when the coating was completely ablated in the centre. (C) 2011 Elsevier B.V. All rights reserved.

Picosecond (40 ps) pulsed Nd:YAG laser irradiation of a WTi thin film on silicon with a wavelength of 532 nm and a fluence 2.1 J/cm(2) was performed in air. This led to significant changes of the chemical composition and morphology on the surface of the WTi thin film. The results show an increase in surface roughness, due to formation of conical structures, about 50 nm wide in the base, and a very thin oxide layer composed of WO(3) and TiO(2), with a dominant TiO(2) phase at the top, within the depth of about 20 nm. The thickness of the oxide layer was dependent on the number of laser pulses. The samples were analyzed by scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy.

A study of morphological and composition changes of the WTi/Si system induced by nanosecond and picosecond laser pulses is presented. A 190 nm thick WTi film was deposited on a silicon substrate of n-type (100). The pulsed laser systems used were: nanosecond TEA CO(2) laser (emission, 10.6 mu m; pulse FWHM; pulse duration 120 ns) and picosecond Nd:YAG laser (emission, 532 nm; pulse FWHM; pulse duration 40 ps). During experiments the used fluences (Phi) had similar values, Phi(1) = 20 J cm(-2) in case of the TEA CO(2) laser and Phi(2) = 16 J cm(-2) for the Nd: YAG laser. The laser-induced morphological and composition modifications showed a dependence on pulse duration. Generally, the following morphological changes were observed: (i) ablation/exfoliation of the WTi thin film, (ii) appearance of hydrodynamic features such as resolidified material, and (iii) formation of nano-sized grains and globules. Overall morphological modifications were more pronounced after the picosecond laser action. The surface composition analysis showed a quite different distribution of sample components depending on the pulse duration. Formation of the silicon dioxide (SiO(2)) was recorded only in the case of irradiation of the WTi/Si system by picosecond laser pulses.

Surface modification of titanium based implant Ti6Al4V induced by an Nd:YAG laser operating at a wavelength of 266 nm, with pulses of 40 ps, is presented. It is shown that the laser beam at fluences 0.96J cm(-2) and 0.29J cm(-2) significantly modifies the alloy surface. The damage threshold is estimated at 0.12 J cm(-2). The irradiations at 0.96J cm-2 were accompanied by the occurrence of plasma. The characteristics of the damage are: (a) smoothed center of the damage area, (b) 20 nm cracks, (c) 200 nm parallel periodic surface structures (PSS). The periodicity of the PSS corresponds to the laser wavelength. Such modifications of the Ti6Al4V implant surface are applicable to medical practice. Surface morphology of the implant was monitored by optical microscopy (OM) and scanning electron microscopy (SEM) coupled to an energy dispersive spectroscopy (EDS) analyzer. (C) 2010 Elsevier B.V. All rights reserved.

Interaction of an Nd:YAG laser, operating at 532 nm wavelength and pulse duration of 40 ps, with tungsten-titanium (WTi) thin film (thickness, 190 nm) deposited on single silicon (100) substrate was studied. Laser fluences of 10.5 and 13.4 J/cm(2) were found to be sufficient for modification of the WTi/silicon target system. The energy absorbed from the Nd:YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following WTi/silicon surface morphological changes were observed: (i) ablation of the thin film during the first laser pulse. The boundary of damage area was relatively sharp after action of one pulse whereas it was quite diffuse after irradiation with more than 10 pulses; (ii) appearance of some nano-structures (e.g., nano-ripples) in the irradiated region; (iii) appearance of the micro-cracking. The process of the laser interaction with WTi/silicon target was accompanied by formation of plasma.

Morphology effects induced during interaction of mu s- (Transversely Excited Atmospheric (TEA) CO(2) laser) or ns- (HF laser) pulses with titanium nitride (TiN) coating, deposited on austenitic stainless steel AISI 316, were studied. Experiments were carried out in regime of focused laser beam in air at atmospheric pressure. The used laser fluences were found to be sufficient for inducing intensive surface modifications of the target. The energy absorbed from the CO(2) as well as HF laser beam is mainly converted into thermal energy, causing different effects like ablation, appearance of hydrodynamic features, etc. Morphology characteristics obtained during ns-pulses irradiation (HF laser) were different to those initiated by mu s-pulses (TEA CO(2) laser). The changes on the target surface in form of massive resolidifed droplets and crown-like structures were observed only for ns- (HF laser) pulses. It was found that these effects are a consequence of higher temperature and better coupling of the HF laser radiation with the target. Recent investigations of ps-Nd:YAG laser interaction with the same TiN coating showed that morphology picture is quite different including the reduction of thermal effect. 9th International Conference on Fundamental and Applied Aspects of Physical Chemistry, Sep 24-26, 2008, Belgrade, Serbia

Interaction of Nd:YAG laser, operating at 266 nm wavelength and a pulse duration of 40 ps, with AISI 1045 steel was studied. Surface damage threshold was estimated to be 0.14 J/cm(2). The steel surface modi. cation was studied at the laser fluence of similar to 1.0 J/cm(2). The energy absorbed from Nd: YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following AISI 1045 steel surface morphological changes and processes were observed: (i) intensive damage of the target in the central zone of irradiated area; (ii) appearance of periodic surface structures at nano-level, with periodicity in agreement with the used wavelength; (iii) reduction of oxygen concentration in irradiated area; and (iv) development of plasma in front of the target. Generally, interaction of laser beam with AISI 1045 steel (at 266 nm) results in a near-instantaneous creation of damage, meaning that large steel surfaces can be modified in short times. (C) 2009 Elsevier B. V. All rights reserved.

Interaction of Nd:YAG laser, operating at 1064 or 532 nm wavelength and a pulse duration of 40 ps, with AISI 1045 steel was studied. Surface damage thresholds were estimated to be 0.30 and 0.16 J/cm(2) at the wavelengths of 1064 and 532 nm, respectively. The steel surface modi. cation was studied at the laser energy density of 10.3 J/cm(2) (at 1064 nm) and 5.4 J/cm(2) (at 532 nm). The energy absorbed from Nd: YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following AISI 1045 steel surface morphological changes and processes were observed: (i) both laser wavelengths cause damage of the steel in the central zone of irradiated area; (ii) appearance of a hydrodynamic feature in the form of resolidified droplets of the material in the surrounding outer zone with 1064 nm laser wavelength; (iii) appearance of periodic surface structures, at micro- and nano-level, with the 532 nm wavelength and, (iv) development of plasma in front of the target. Generally, interaction of laser beam with the AISI 1045 steel (at 1064 and 532 nm) results in a near-instantaneous creation of damage, meaning that large steel surfaces can be processed in short time. (C) 2008 Elsevier B. V. All rights reserved.

The interaction of Ti:sapphire laser, operating at high repetition rate of 75 MHz, with nickel-based super-alloy Inconel 600 was studied. The laser was emitting at 800 nm and ultrashort pulse duration was 160 fs. Nickel-based super-alloy surface modification was studied in a low laser energy/fluence regime of maximum 20 nJ–15 mJ/cm2, for short (10 s) and long irradiation times (range of minutes). Surface damage threshold of this material was estimated to be 1.46 nJ, i.e., 0.001 J/cm2 in air. The radiation absorbed from Ti:sapphire laser beam under these conditions generates at the surface a series of effects, such as direct material vaporization, plasma creation, formation of nano-structures and their larger aggregates, damage accumulation, etc. Laser induced surface morphological changes observed on Inconel 600 were: (1) intensive removal of surface material with crater like features; (2) material deposition at near and farther periphery and creation of nano-aggregates/nano-structures; (3) sporadic micro-cracking of the inner and outer damage area. Generally, features created on nickel-based super-alloy surface by high repetition rate femtosecond pulses are characterized by low inner/outer damage diameter of less than 11 µm/30 µm and relatively large depth on the order of 150 µm, in both low (10 s) and high (minutes) irradiation time regimes.

Interaction of pulsed femtosecond Ti:sapphire laser (160 fs), operating at high repetition rate (75 MHz) at 800 nm, with nickel-based superalloy Inconel 600 and tungsten-titanium (WTi) target was studied. The WTi target was in form of thin film deposited on silicon substrate. Low laser fluence of maximum 50 mJ/cm(2) had modified the target surface during irradiation/exposure time of seconds or minutes. The radiation absorbed from the laser beam generates at the surface a series of effects, such as direct material vaporization, formation of clusters, etc. Morphological features of the targets can be summarized as: (a) intensive removal of material and crater appearance; (b) creation of nanostructures; (c) microcracking, etc. Ablation of Inconel 600 surface is effective, resulting in formation of holes with small diameter ( LT = 10 mu m) and relatively large depth ( LT = 50 mu m). In case of WTi target/thin film, the surrounding rim is not so expressed, and crater depths are lower. It can be concluded that the average laser power of the order of watts, pulse energies of the order of nanojoules and high repetition rates (MHz range) can successfully modify metallic materials. International School and Conference on Photonics (PHOTONICA09), Aug 24-28, 2009, Belgrade, Serbia