High-temperature metallization of the Ge(111) surface detected by photoemission spectroscopy

The 3d core levels and the valence band of Ge(lll) have been studied by photoemission as a function of temperature up to 1200 X. Evidence of a phase transition is found between 1020 K and 1085 K from core level analysis. For 1020 K < T < 1200 K the data can be interpreted consistently with an incomplete surface melting scenario. A finite density of states at the Fermi level indicates a metallic surface layer above this phase transition. About 0.7-1 atomic bilayer is estimated to undergo the semiconductor-to-metal transition.