GROWTH AND ATOMIC-STRUCTURE OF EPITAXIAL SI FILMS ON GE(111)

Heteroepitaxial growth by molecular beam epitaxy of thin Si films on the Ge(111) surface was studied. The surface morphology and atomic structure were examined by scanning tunneling microscopy and synchrotron-radiation photoemission. For submonolayer Si coverages on the Ge(111) substrate at room temperature, the impinging Si atoms condense to form small islands. The areas surrounding the islands remain c(2 x 8). Post annealing or growth at high temperatures causes Si indiffusion and Ge segregation to the surface. Multilayer deposition at high temperatures can be described as a mixed two- and three-dimensional growth. Many small three-dimensional islands are observed on a two-dimensional film. The surface structure of the film shows partial disorder, and the film itself contains numerous defects caused by the lattice mismatch between Si and Ge. The role of the segregated Ge as a surfactant in the growth is discussed.