Strained Ge/Si(001) interface in the presence of Bi and Sb surfactants

The adsorption of Ge on the Bi/Si(001)2x5 surface (Bi saturation coverage o f 0.7 ML) and on Sb/Si(001)2x1 (Sb saturation coverage of 0.9 ML), was inve stigated by core level photoemission spectroscopy. For the Bi/Si(001)2x5 in terface, at submonolayer Ge coverage, the presence of a bulk component larg ely dominating the Ge 3d core level, demonstrates that the favorite adsorpt ion sites are the Bi-terminated terraces, where the Ge-Bi site exchange tak es place. At larger Ge coverage, in addition to the previous process, the o ccurrence of a pure Ge epitaxy on the bare fraction of the substrate is ind icated by the presence of the 2x1 surface components in the Ge 3d core leve l. In the case of Sb/Si(001)2x1 interface, the Ge 3d shows a complete lack of surface components, which indicates the absence of dimerized Ge atoms at the top layer, and demonstrates that the Ge-Sb site exchange process has t aken place on the whole Si(001) surface. (C) 1999 Elsevier Science B.V. All rights reserved.