Mechanisms of pit coarsening in ion erosion of fcc(1 1 1) surfaces: a kinetic 3D lattice Monte-Carlo study

An atomic simulation approach to ion erosion of fcc(1 1 1) surfaces is presented. In a fully 3D kinetic lattice Monte-Carlo model thermodynamically activated processes like adatom, step-edge or surface vacancy diffusion are combined with ballistic effects due to single ion impacts, i.e. sputtering, adatom and surface vacancy generation. In the course of erosion nucleation of surface vacancy islands, their growth, both laterally and vertically, and subsequent coarsening of these pits is observed. For removal of up to Θ=6 monolayers the evolution of the surface is characterized in terms of the roughness and height–height correlation function. The simulation results are discussed with respect to low-energy noble gas ion erosion experiments of Pt(1 1 1) surfaces [M. Kalff et al., Surf. Sci. 486 (2001) 103, preceding paper]. By explicitly tuning specific atomic transitions within the simulation it is demonstrated, that forbidden thermal adatom generation does hardly influence the surface evolution. Suppressed step-edge diffusion, however, considerably slows down pit coarsening and impedes pit shape relaxation, emphasizing the importance of this smoothening process in ion erosion.