Finite element analysis of the initial stages of the laser ablation process (original) (raw)
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Analysis of plume deflection in the silicon laser ablation process
Applied Physics A, 2007
Changes in target surface morphology and ablation plume direction have been experimentally observed during the initial stages of the silicon laser ablation process. A relationship between both phenomena can be observed upon analysing the temperature field induced by the laser beam in a rough surface material. Theoretical studies on the deflection of the ablation plume are presented. These analyses are based on the hypothesis that particles that reach evaporation temperature will exit normally to the target surface with a velocity that is proportional to the surface temperature and the amount of the ablated material. Numerical solutions and experimental results of laser ablation process of silicon targets are found to agree with theoretical studies. PACS 42.25.Lc; 79.20.Dc; 02.70.Dc
Applied Surface Science, 1996
In this work, the spatial distribution of laser-generated species in vacuum from a monoatomic target is deduced from the analytical resolution of the hydrodynamic equations for a plasma expanding in the adiabatic regime. The thickness distribution of the laser deposited layers is demonstrated to be related to the initial dimensions of the plasma but independent of both the laser fluence and the atomic mass of the target element. From these calculations, we also deduced an angular distribution of the deposits as a sum of cosTI. These theoretical results are experimentally supported in the specific case of the pulsed excimer laser ablation of Si and Ge monoatomic targets.
Detailed studies of the plume deflection effect during sub-ps laser ablation of Si target
Applied Surface Science, 2005
For the first time the plume deflection effect during the irradiation of silicon target with sub-ps KrF laser pulses was investigated. The morphological changes of the laser ablated target and the corresponding plume deflection angle have been studied in vacuum with different laser fluences and number of pulses. In accordance with earlier results obtained by nanosecond laser, we found a strong correlation between the morphological changes on the irradiated target and the observed plume deflection angle. As the number of laser pulses increases, the formation of well-defined silicon columnar microstructures oriented towards the laser beam has been observed on the targets ablated with fluences between 0.1 and 1.7 J/cm 2 (2.2 Â 10 11 and 37.4 Â 10 11 W/cm 2 of power density, respectively). It has also been observed that the plume deflection effect is present for laser fluences between 0.1 and 1.2 J/cm 2 , with a maximum deflection angle always higher than 208. Simultaneously, an array of silicon substrates placed on a hemi-cylindrical holder was used for deposition experiments, in order to study the influence of the plume deflection on the thickness distribution profile of the deposited films. Profilometric analyses of the deposited silicon films revealed a non-uniform material deposition. Comparison with the results obtained by nanosecond lasers is reported and discussed.
Science of Sintering, 2008
Using electron microscopy, atomic force microscopy, X-ray microanalysis, and IR spectroscopy, it was established that, in the regime of continuous laser irradiation of silicon at P = 170 W in different gaseous atmospheres with an oxygen impurity, SiO x composite films with a complex morphology form. The main components of ablation products are clusters that form during flight of ablation products and as a result of separation of SiO x -clusters from the zone of the irradiation channel. The roughness and density of the films depend on the heating temperature of the target surface and the type of deposited clusters.
Analysis of the formation and evolution of oriented microstructures on laser ablated silicon
Applied Physics A, 2008
A theoretical approach and qualitative analysis of the changes induced on the surface morphology and the formation of microstructures on silicon targets irradiated by excimer laser are presented. This study is based on theoretical principles of the laser ablation process, in particular, on the analysis of the contribution of the laser energy density, which involves the laser beam parameters and also the physical properties of the target material. For different laser incident angles, the formation of micro-columns oriented towards the laser incident direction is explained. Moreover, numerical simulations and ablation experiments carried out with an excimer laser corroborate the theoretical analysis.
Dynamical modeling of laser ablation processes
1995
Several physics and computational approaches have been developed to globally characterize phenomena important for film growth by pulsed laser deposition of materials. These include thermal models of laser-solid target interactions that initiate the vapor plume; plume ionization and heating through laser absorption beyond local thermodynamic equilibrium mechanisms; gas dynamic, hydrodynamic, and collisional descriptions of plume transport; and molecular dynamics models of the interaction of plume particles with the deposition substrate. The complexity of the phenomena involved in the laser ablation process is matched by the diversity of the modeling task, which combines materials science, atomic physics, and plasma physics.
Nanostructuring of Material Surfaces by Laser Ablation
Radiation Effects in Materials, 2016
Irradiation of materials such as iron and silicon with single nanosecond laser pulses produces nanostructures on its surfaces. Nevertheless, the deposition before irradiation of thin films on the surface of the silicon wafers can modify the shapes of these structures. Upon laser irradiation, different effects are produced on the surfaces of monocrystalline silicon wafers coated with a thin film of Si 3 N 4 than on that of bare ones. After irradiation with a Nd:YAG laser pulse of 532 nm, the coated silicon surface presents a nanostructure that, due to its hydrophobic behavior, can be used for biological applications such as cell growth. On the other hand, the nanostructures formed on the surface of metals, such as iron, make them more resistant to oxidation processes by changing their oxidation potentials.
Computational and experimental study of nanosecond laser ablation of crystalline silicon
International Communications in Heat and Mass Transfer, 2011
In this paper, a numerical model of nanosecond laser ablation of crystalline silicon has been established. Based on the highly nonlinear model of heat transfer and phase change in crystalline silicon after absorbing laser light, heat transfer equation is solved by using finite element method implemented in ANSYS. The simulation of ablation depth of crystalline silicon is obtained under different conditions of laser fluence and pulse overlap. Comparing with the ablation morphology obtained from SEM observations, the computational results and experimental data show good agreement.
Pulsed laser ablation and deposition of thin films
Chemical Society Reviews, 2004
Pulsed laser ablation is a simple, but versatile, experimental method that finds use as a means of patterning a very diverse range of materials, and in wide areas of thin film deposition and multi-layer research. Superficially, at least, the technique is conceptually simple also, but this apparent simplicity hides a wealth of fascinating, and still incompletely understood, chemical physics. This overview traces our current physico-chemical understanding of the evolution of material from target ablation through to the deposited film, addressing the initial laser-target interactions by which solid material enters the gas phase, the processing and propagation of material in the plume of ejected material, and the eventual accommodation of gas phase species onto the substrate that is to be coated. It is intended that this Review be of interest both to materials scientists interested in thin film growth, and to chemical physicists whose primary interest is with more fundamental aspects of the processes of pulsed laser ablation and deposition.
Characterization of laser ablated silicon thin films
1999
Using laser ablation, we deposited silicon layers consisting of clusters and crystalline domains onto glass, quartz, aluminum, titanium, copper, single-crystal silicon and single-crystal potassium bromide substrates. The microstructure and the morphology of the ®lms were characterized by use of optical microscopy, laser scanning microscopy, atomic force microscopy, transmission electron microscopy, micro-Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The results indicated that the deposited material was composed of microcrystalline droplets, typically 3.5 mm in diameter, separated by amorphous-like regions. The droplets were composed of crystalline material at their centers and an outer halo of nanometer-size particles. q