The atomic geometry of the Ge(111) surface as a function of temperature studied by photoemission and photoelectron diffraction

Photoelectron diffraction of the bulk and surface components of the Ge 3d core-level has been measured from the Ge(111)- c (2 × 8) reconstructed surface at room temperature and on the Ge(111)-(1 × 1) surface at 400°C. Calculations show good agreement with the results of recent X-ray diffraction work on the c(2 × 8) surface. Results for the (1 × 1) surface show no change in the short-range structure at the surface across the phase transition suggesting that the adatom-restatom building block structure accepted for the c(2 × 8) surface remains intact after the phase transition. This method of measuring the photoelectron diffraction from resolved surface core-levels provides a direct method for assigning these levels to specific species at the surface. In addition, significant variations in the branching ratios as a function of azimuthal angle have been found which are due to differences in the final state for the two spin-orbit components of the Ge 3d photoemission peak.