The adsorption and diffusion of Ge adatoms and ad-dimers on the one-monolayer Sb-covered Si(001) surface were studied using first-principles total-energy calculations. It was shown that Ge adatoms and ad-dimers could both break Sb dimers because of the weak bonding of the Sb dimers on Si(001). As a result, the most stable sites were both on the Sb dimer rows for Ge adatoms and ad-dimers, which was in significant contrast to the conventional picture that the most stable site for a Ge ad-dimer was in the trough between the group-V element dimer rows. The energetics of the site exchange between Ge and Sb atoms for the surfactant-mediated growth were also examined and it was found that Ge ad-dimers tended to exchange with the sub-surface Sb atoms one-by-one perpendicular to the surface dimer rows.

Adsorption, Diffusion and Site Exchange for Ge Ad-Dimers on Sb-Covered Si(001) from First-Principles Total-Energy Calculations. E.Z.Liu, C.Y.Wang, J.T.Wang: Physical Review B, 2006, 74[7], 075303 (5pp)