Combined ab initio and kinetic Monte Carlo simulations of C diffusion on the ?3 X ?3 ?-SiC(111) surface

We investigate the kinetic behavior of a single C adatom on the root 3 x root 3 beta-SiC(111) surface by means of combined ab initio and kinetic Monte Carlo simulations. After identifying the metastable binding locations, we calculate the energy barriers the adatom must overcome when jumping among them. The presence of the root 3 x root 3 reconstruction creates considerable differences among the diffusion mechanisms that can be thermally activated. This has important implications for the C mobility on the surface, and therefore for SiC growth. The kinetic simulation at realistic temperatures and time scales revealed that C diffusion occurs mostly around the Si adatoms forming the root 3 x root 3 reconstruction. A reduced adatom mobility, as observed in many studies of surfactant-mediated growth, can favor the formation of a high density of nuclei, and thus promote a layer-by-layer growth. As a further result of the kinetic simulation we obtained the adatom diffusion coefficient, a macroscopic quantity accessible in experiments.