EVIDENCE FOR AN ORDER-ORDER TRANSITION ON THE GE(111) SURFACE NEAR 1050 K FROM HIGH-RESOLUTION HELIUM ATOM SCATTERING EXPERIMENTS

Helium atom scattering has been used to investigate the Ge(111) surface phase transition at Tc=1050 K. The elastically scattered helium atoms show sharp, integral-order diffraction peaks that change only in their relative amplitudes at Tc and persist up to 1160 K, the highest temperature studied. Contrary to previous reports based on low-energy electron and x-ray diffraction, ion backscattering, and a recent theoretical study, the present findings show that the surface remains highly ordered above Tc, with a reduced height of the top bilayer, and that it may be metallic as was recently observed in electron energy loss spectroscopy. © 1995 The American Physical Society.