STM observation of pit formation and evolution during the epitaxial growth of Si on Si(001) surface

Pit formation and surface morphological evolution in Si(001) homoepitaxy are investigated by using scanning tunneling microscopy. Anti-phase boundary is found to give rise to initial generation of pits bound by bunched D_B steps. The terraces break up and are reduced to a critical nucleus size with pit formation. Due to anisotropic kinetics, a downhill bias diffusion current, which is larger along the dimer rows through the centre area of the terrace than through the area close to the edge, leads to the prevalence of pits bound by 101 facets. Subsequent annealing results in a shape transition from 101-faceted pits to multi-faceted pits.