GROWTH OF GE THIN-FILMS AND ISLANDS ON THE SI(001) SURFACE

We study strained-layer growth of Ge on the Si(001) surface by means of an empirical potential that is further refined by fitting it to recent total-energy results for the stress and energies of various missing-dimer reconstructions of the Si(001) surface. The modified potential predicts the buckled dimer surface to be substantially lower in energy than the symmetric dimer surface. It is seen that the reconstruction of the GeSi surface, before the occurrence of islanding, has the missing-dimer-trench structure as observed in a number of scanning tunneling microscopy experiments. Our calculations provide direct support to the notion that islanding does indeed set in after layer-by-layer growth of three monolayers. We discuss the implications of our calculations for the growth of long thin islands of high aspect ratios as seen recently in Ag-on-Si(001) systems which has been attributed to elastic relaxation.