Gallium-induced nanostructures on Si(111): From magic clusters to incommensurate structures

Scanning tunneling microscopy is used to study the nanostructures that are induced within the √3×√3R30^∘ Ga/Si(111) surface by the deposition of the submonolayer of Ga and subsequent annealing. Triangular magic clusters and incommensurate islands are found after annealing at low and high temperatures, respectively. The clusters and islands have similar atomic configurations and their surrounding √3×√3 R30^∘ adatom lattices also exhibit similar characteristic vacancy patterns. A type of structural model is proposed for both the clusters and islands. The model provides some insights about the structural evolution, from the √3×√3 monolayer to the incommensurate bilayer structure, that is induced by increasing local Ga coverage.