Ab initio study of epitaxial growth on stepped Si(100) surface

Diffusion of a Si adatom over the reconstructed Si(100) surface with a single-height step on it is studied using the pseudopotential total energy method. The S-B rebonded step is shown to act as a good sink for adatoms descending onto the lower ledge. This is due to the presence of deep traps on the lower terrace and to the negative Ehrlich-Schwoebel barrier (the activation barrier for descent from the edge is 0.23 eV lower than for the motion on a flat surface). The diffusion characteristics of the adatom on both terraces are virtually unaffected by the presence of the step. However, the dimer buckling sequence on a lower terrace is strongly dependent on the position of the adatom along the diffusion path. (C) 1997 John Wiley & Sons, Inc.