A simulation was performed, using a density functional method, of adatom diffusion on a flat (001) c(4 x 2) surface and around a single type of surface step (SA). The results indicated that a moderate additional energy barrier of 0.2eV had to be surmounted in order to cross the SA step; as compared with the energy for diffusion on a flat surface. The dimer-top lattice site on the lower terrace adjacent to the step edge was stabilized by 0.15eV with respect to the flat surface value, although the most stable binding sites near to the step were unaffected. This behavior was explained in terms of the disruption of dimer tilt near to the step. The results suggested that adatoms were more likely to stop on lattice sites at the SA step edge than on lattice sites on the open surface. This could affect the relative dimer formation rate near to the step, with respect to the behavior on the flat surface; even in the absence of a clear change in binding energy. The effect of the SA step terrace edge upon adatom behavior was very short-ranged and weak. This was considered to be consistent with the relatively small strain field and lack of change in dangling-bond density which was associated with the step edge.

J.Wang, D.A.Drabold, A.Rockett: Applied Physics Letters, 1995, 66[15], 1954-6