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 root 3 x root 3R30 degrees Ga/Si(111) surface by the dep osition of the submonolayer of Ga and subsequent annealing. Triangular magi c clusters and incommensurate islands are found after annealing at low and high temperatures, respectively. The clusters and islands have similar atom ic configurations and their surrounding root 3 x root 3 R30 degrees adatom lattices also exhibit similar characteristic vacancy patterns. A type of st ructural model is proposed for both the clusters and islands. The model pro vides some insights about the structural evolution, from the root 3 x root 3 monolayer to the incommensurate bilayer structure, that is induced by inc reasing local Ga coverage. [S0163-1829(99)05227-3].