Structure and stability of Ge cluster on Si(111) surface in the presence of Bi surfactant

Submonolayer Ge cluster grown by molecular beam epitaxy on the Si(111)-3×3-Bi surface were studied using scanning tunneling microscopy. The cluster of monolayer and bilayer height containing 3-4 and 9-10 atoms, respectively, have been grown at room temperature. We have found that the monolayer cluster are mobile and diffuse over Bi layer at room temperature, while bilayer cluster are epitaxial and can be classified by positions of the cluster relative to Bi trimers on the Si(111)-3×3-Bi surface. In the temperature range of 100 °C-400 °C, the cluster population consists of two types of bilayer cluster with Bi trimers in T4 and H3 positions on the cluster, correspondingly. At temperatures above 400 °C only the most stable atomic configuration with Bi trimer in H3 position on the bilayer cluster is remained on the surface.