High-temperature phase transitions at the Ge(110) surface

The Ge(110) surface has been investigated by core-level and valence band (VB) photoemission spectroscopy as a function of the temperature starting from the room temperature c(8×10) reconstructed surface up to 1196 K. Evidence of a phase transition is found at about 750±50 K from core-level and VB data analysis. VB photoemission shows that above 750 K the Ge(110) surface acquires an increasing metallic character up to 1110 K where a sudden, intense jump of the emission intensity at the Fermi level is observed. At higher temperatures up to 1196 K, a finite and constant density of states is observed, indicating the presence of a metallic surface layer.