X-ray absorption spectroscopy and valence band photoemission spectroscopy investigations of the Ge(111) surface above the 1050 K high-temperature phase transition

The Ge(111) surface has been investigated as the temperature was varied in the 300 K - 1150 K range by valence band (VB) photoemission spectroscopy and x-ray absorption spectroscopy above the Ge 3d edge. VB photoemission shows that the high-temperature surface has a metallic character and that at temperatures above the 1050 K high-temperature phase transition a clear change of the surface electronic structure occurs. Metallicity at high temperature was also detected by absorption spectroscopy which shows the presence of a well-defined Fermi edge at an energy value consistent with earlier core photoemission results. From absorption data and numerical simulations the width of the Ge(111) surface conduction band was found to be 1.1 eV.