Theoretical evidence concerning mixed dimer growth on the surface

Abstract

The local atomic geometry, chemical bonding and energetics for half- and full-monolayer Ge coverages on the surface have been studied by applying the ab initio pseudopotential method. For one monolayer coverage we find that the adatoms form an asymmetric dimer with length equal to the bond length in bulk Ge. At half-monolayer coverage we find that the formation of mixed Si - Ge dimers is comparable to growth of Ge - Ge dimers in islands, confirming recent experimental observations. Our work also shows that Ge diffusion into the substrate will only become important at unusually high growth temperatures, in the region of 1000 K or above.