Ge(111) [formula omitted]: The atomic geometry

Abstract

We have performed surface X-ray diffraction experiments on submonolayer coverages of Pb on Ge(111) using the wiggler beamline at the Hamburger Synchrotronstrahlungslabor (HASY-LAB). Two 3 × 3 R30° Pb structures at different coverages have been identified. In the dilute structure there is only one atom per unit cell, the dense structure is a distorted close packed overlayer. Relating the scattering from the Pb overlayers with that from the underlying Ge crystal provides a novel method for determining the registry of the overlayers. We observe a difference in chemisorption site between the dilute and the dense phase.