Surface morphology formation of Ge layers on Si(111) under high-temperature annealing

Evolution of surface morphology of Ge layers on the Si(111) surface under high-temperature annealing is studied with scanning tunneling and electron microscopies. It is found that the morphology with three-dimensional Ge islands obtained by the Ge deposition at the relatively low temperatures of 450-500 °C transforms into a net of continuous ridges after annealing at 700-950 °C. This indicates that the annealing leads to the separation of Ge and Si phases. Such a transformation reduces simultaneously the Ge/Si interface and free surface areas. The calculations show that this provides the total energy reduction up to about 30%, leading to the formation of stable surface morphology.