Modeling of surface roughening induced by laser ablation

摘要

Laser-induced disordering of a model solid surface was simulated using the Monte Carlo method. The roughening of the surface was monitored in the course of the simulation and it was compared with analytical solutions obtained by means of a suitably modified version of the Random Deposition (RD) model. In particular, the influence of the number of laser pulses and the dimensions of a cubicoid crater produced by a single pulse on the structural and adsorptive properties of the surface were studied. It was demonstrated that the mean surface depth and the interface width can be expressed by simple functions of the number of laser scans, regardless of the assumed crater dimensions. A similar finding was obtained in the case of the depth distribution functions as well as for the average number of contact points per lattice site. The latter quantity, which defines the number of vertical facets surrounding a molecule adsorbed on a given lattice site, was found to have substantial effect on the energetic properties of the surface. A detailed analysis of the population of sites with different number of contact points was also performed. This procedure enabled the calculation of temperature programmed desorption (TPD) spectra of monomolecular adsorbates from surfaces subjected to a different number of laser scans. The spectra calculated using the absolute rate theory (ART) were also compared with the result of the Monte Carlo simulations carried out for the same systems. Good quantitative matches between the ART and the simulations were obtained in all the cases studied.