The Ge(111) surface has been studied by photoemission and photoabsorption spectroscopies as a function of temperature up to 1200 K. Up to 1020 K the data indicate the presence of an adatom-restatom reconstruction, with a gradual weak metallization of the surface between 600 and 1020 K. Evidence for a high-temperature phase transition is found between 1020 and 1085 K from core-level spectroscopy. Valence-band photoemission spectra and photoabsorption data indicate a metallic surface layer above this phase transition. About 0.7–1 atomic bilayer is estimated to undergo the semiconductor to metal transition. All these data can be interpreted consistently with an incomplete surface-melting scenario.
