Ge/Bi/Si(001)-c(4 × 2) interface studied by high-resolution core-level spectroscopy

The adsorption of germanium on the Bi/Si(001)-(2 × 5) surface [bismuth saturation coverage of 0.7 ML (monolayers)] was investigated by core-level photoemission spectroscopy. At submonolayer germanium coverage, the presence of a bulk component largely dominating the Ge 3d core level demonstrates that the favourite adsorption sites are the bismuth-terminated terraces, where Ge-Bi site exchange takes place. At larger germanium coverage, in addition to the previous process, the occurrence of a pure germanium epitaxy is indicated by the presence of the (2 × 1) surface components in the Ge 3d core level.