Scanning tunnelling microscopy was used to study the anisotropy of the surface diffusion of Ge and Si on the (001) plane of Si. This was done by analyzing the denuded zones around steps in the spatial distribution of 2-dimensional islands which formed after sub-monolayer deposition. It was found that, in both cases, diffusion was some 1000 times faster along the dimer row direction than perpendicular to it. It was also found that SB steps were good sinks for Si and Ge adatoms, whereas SA steps were not. Moreover, SB steps appeared to be symmetrical sinks for adatoms coming from either the down terraces or the up terraces.

Y.W.Mo, M.G.Lagally: Surface Science, 1991, 248[3], 313-20