Ultrathin films of Ge on the Si(100)2 × 1 surface

Abstract

The Ge/Si(100)2 × 1 interface was investigated by means of Auger electron spectroscopy, low‐energy electron diffraction, thermal desorption spectroscopy, and work function measurements, in the regime of a few monolayers. The results show that growth of Ge at room temperature forms a thermally stable amorphous interface without significant intermixing and interdiffusion into the substrate, for annealing up to ~1100 K. Therefore, the Ge‐Si interaction most likely takes place at the outmost silicon atomic plane. The charge transfer between Ge and Si seems to be negligible, indicating a rather covalent bonding. Regarding the Ge overlayer morphology, the growth mode depends on the substrate temperature during deposition, in accordance with the literature. Stronger annealing of the germanium covered substrate (>1100 K) causes desorption of not only Ge adatoms, but also SiGe and Ge2 species. This is probably due to a thermal Ge‐Si interdiffusion. In that case, deeper silicon planes participate in the Ge‐Si interaction. Above 1200 K, a new Ge superstructure (4 × 4)R45o was observed. Based on that symmetry, an atomic model is proposed, where Ge adatom pairs interact with free silicon dangling bonds.