Surface thermal expansion of Ge(111)

Abstract

The thermal expansion of the Ge(111) surface has been measured by reflection high-energy electron diffraction (RHEED) based on a simple kinematic model. Measurements of the RHEED streak shift towards the shadow edge gives a thermal expansion perpendicular to the Ge(111) surface, about 11 times that of the bulk over the temperature range from 300K to 600K. The Debye–Waller extinction of the RHEED streak intensity with temperature gives an effective surface Debye temperature of 96±11K for Ge(111). The enhanced thermal expansion perpendicular to the Ge(111) surface is expected to result from the weakening of the harmonic restore force constant of the interlayer potential.