This research is concerned with fundamental problems involving the growth and characterization of thin heteroepitaxial germanium films on crystalline silicon substrates with a (100) orientation which exhibits a 2 x 1 surface reconstruction. Recent theoretical and experimental studies have given support for dramatic changes in the electronic band structure of germanium/silicon systems resulting from changing the strain and superlattice composition on an atomic scale. This group has found evidence for pseudomorphic domains in germanium films on silicon grown at room temperature. It is now proposed to investigate the structure of thin germanium films on silicon grown at low temperatures and also as a function of temperature. This work involves a unique combination of analytic techniques: transmission ion channeling, scanning tunneling microscopy, low energy electron diffraction, and Auger electron spectroscopy. A second emphasis will involve the surface chemistry of adatoms on strained germanium. It is hoped one can distinguish the seperate roles played by chemistry, geometry, and strain in determining the bonding site of the adatom. Initially tin and sulfur will be employed as adatoms.
