Using first-principles total-energy calculations, the adsorption and diffusion of Si and Ge adatoms on Ge/Si(001)-(2x8) and Ge/Si(105)-(1x2) surfaces were investigated. The dimer vacancy lines on Ge/Si(001)-(2x8) and the alternate SA and re-bonded SB steps on Ge/Si(105)-(1x2) were found to influence strongly the adatom kinetics. On Ge/Si(001)-(2x8) surface, the fast diffusion path was found to be along the dimer vacancy line, reversing the diffusion anisotropy on Si(001). Also, there existed a repulsion between the adatom and the dimer vacancy line, which was expected to increase the adatom density and hence island nucleation rate in between the dimer vacancy lines. On Ge/Si(105)-(1x2) surface, the overall diffusion barrier of Si(Ge) along (501) direction was relative fast with a barrier of about 0.83(0.61)eV, despite of the large surface undulation. This indicated that the adatoms could rapidly diffuse up and down the (105)-faceted Ge hut island. The diffusion was also almost isotropic along [010] and [¯501] directions.

First-Principles Study of Adsorption and Diffusion on Ge/Si(001)-(2×8) and Ge/Si(105)-(1x2) Surfaces. L.Huang, G.H.Lu, F.Liu, X.G.Gong: Surface Science, 2007, 601[14], 3067-72