Scanning tunneling microscopy study on the oxidation and annealing of Ga/Si(111)

Abstract

The oxidation and annealing of Ga/Si(111) surfaces with a coverage below 1 ML have been investigated by scanning tunneling microscopy (STM). Various gallium-induced phases from a partially -R30°-covered 7×7 structure (less than 1/3 ML) to a fully covered Ga/Si bilayer (close to 1 ML) were successfully prepared on Si(111) surfaces. Oxygen exposure at elevated temperatures induced a structural change in the bilayer phase, in which etching seems to start from the domain boundaries of the tiled bilayer structure. After 200 L oxygen exposure, the bilayer changed to randomly distributed nanocluster-like and nanoparticle-like structures. The evolution of the oxidized surface induced by annealing in ultrahigh vacuum suggests the formation of volatile compounds such as Ga2O and SiO.