The motion of Si atoms at a Si(100) surface is investigated on both short ( 1ps) and long (1 s) time scales. It is found that silicon atoms in the surface layer can form dimers within a time of order 1 ps. An interesting switching between symmetric and asymmetric dimers is observed in some runs. In others, the coexistence of symmetric and asymmetric dimers is observed. On a long time scale, stochastic modeling is used to simulate adsorption, diffusion, and growth. While deposition of Si atoms continues on vicinal Si(100), there is a tendency toward a one-domain surface with double steps. When deposition is turned off, diffusion leads to a two-domain surface with single steps. These conclusions are consistent with recent scanning tunneling microscopy and reflection high-energy electron diffraction observations.
