A combined molecular dynamics and kinetic Monte Carlo calculation to study sputter erosion and beam assisted deposition

To extend the time scale in molecular dynamics (MD) calculations of sputtering and ion assisted deposition we have coupled our MD calculations to a kinetic Monte Carlo (KMC) calculation. In this way we have studied surface erosion of Cu(1 0 0) under 200-600 eV Cu ion bombardment and growth of Cu on Cu(1 0 0) for deposition at thermal energies up to energies of 100 eV per atom. Target temperatures were varied from 100 to 400 K. The coupling of the MD calculation to a KMC calculation allows us to extend our calculations from a few ps, a time scale typical for MD, to times of up to seconds until the next Cu particle will impinge/be deposited on the crystal surface of about 100 nm2 in size. The latter value of 1 s is quite realistic for a typical experimental sputter erosion or deposition experiment. In such a calculation thermal diffusion processes at the surface and annealing of the surface after energetic ion bombardment can be taken into account. To achieve homo-epitaxial growth of a film the results clearly show the important influence of deposition at non-thermal energies like in sputter or beam assisted deposition as compared to a purely thermal deposition. The optimum energy per atom for homo-epitaxial growth of Cu on Cu (at 100 K) was found to be around 20 eV. In sputter erosion for 600 eV Cu bombardment of Cu(1 0 0) at 400 K we found layer by layer erosion at very low ion fluxes changing into the development of a pronounced surface structure at high ion fluxes