Monte Carlo simulation of pulsed laser ablation from two-component target into diluted ambient gas

Abstract

International audienceLaser ablation from a binary target into a diluted gas background is studied by means of a Monte Carlo simulation. The influence of the ambient gas on the spatial and mean energy distribution of particles deposited at the distant detector is considered. Thermalization of the particles, the random scattering effect and the backscattering of particles were observed. Considerable modification of the deposited film thickness profiles due to collisions of the ablated particles with the ambient gas is shown. The increase of the ambient gas pressure was found to affect the stoichiometry distribution of deposited and backscattered particles. The study is of a particular interest for the development of the thin film growing technique known as pulsed laser deposition

Atomic/Molecular-Level Simulations of Laser–Materials Interactions

“…For investigation of the long-term expansion of the ablation plume, in particular, a combination of MD with the DSMC method [195] has been demonstrated to be a promising approach capable of following the evolution of the parameters of the ablation plume on the scales, characteristic for experimental conditions, up to hundreds of microseconds and millimeters [50][51][52][53][54][55]. In the combined MD-DSMC model [78,185,187,[196][197][198][199], MD is used for simulation of the initial stage of the ablation process (first nanoseconds) and provides the initial conditions for DSMC simulation of the processes occurring during the long-term expansion of the ejected plume.…”

“…The latter nonequilibrium kinetic description has been shown to be necessary for subnanosecond pulses, when a fast thermal energy flow to/from the liquid-solid interface creates conditions for significant overheating/undercooling of the interface [43,44]. The material removal from the target can be incorporated into continuum models in the form of surface or volumetric vaporization models, e.g., [45][46][47][48][49], whereas the expansion of the vaporized plume is commonly described by solving gas dynamics equations, e.g., [45][46][47][48][49] or using the Direct Simulation Monte Carlo (DSMC) technique, e.g., [50][51][52][53][54][55]. Hydrodynamic computational models based on multiphase equations-of-state have also been used for simulation of laser melting, spallation, and ablation [56][57][58][59][60][61][62].…”

Computer Simulations of Laser Ablation of Molecular Substrates

“…Among several alternative methods that can be considered for simulation of the long-term ablation plume expansion, part D in Figure 1, the direct simulation Monte Carlo (DSMC) method [122][123][124][125][126][127][128] appears to be the most suitable technique for neutral or weakly ionized ablation plumes. The continuum description, based on the finite element solution of the Navier-Stokes equations, is well suited for highdensity collision-dominated flows but is not appropriate for the low densities realized in the rapidly expanding ablation plumes.…”

Pulsed laser ablation of complex oxides: The role of congruent ablation and preferential scattering for the film stoichiometry

“…8 Figure 1 also exemplifies that at a given fluence, e.g., F ¼ 1.5 J/cm 2 , the films can be nearly stoichiometric (D TS ¼ 44 mm) but also extremely non-stoichiometric with a Ti-rich (D TS ¼ 40 mm) or a Sr-rich (D TS ¼ 48 mm) composition, depending on the target-to-substrate distance. This is a hint that the puzzling variation of the STO film stoichiometry results from an intricate combination between preferential scattering of light plume species, e.g., Ti in STO, during their flight towards the substrate 14 and incongruent ablation of the STO target that compensates for scattered species. Any influence of re-sputtering processes on the film stoichiometry can be excluded 15 due to the rather low kinetic energy of the plume species reaching the substrate located at a distance of several cm, 16 at a deposition pressure of %10 À1 mbar.…”