Structure and phases of the Au(001) surface: Absolute x-ray reflectivity

Specular and nonspecular absolute x-ray-reflectivity measurements have been performed on the Au(001) surface between T=300 and 1250 K. At all temperatures the surface-normal vibrational amplitudes are increased above the corresponding bulk thermal vibrational amplitude (Debye-Waller factor). Below T=1170 K, the surface is well described by an incommensurate, corrugated, hexagonal overlayer. The corrugation propagates several layers into the bulk. Above T=1170 K there is an abrupt decrease in the specular and nonspecular reflectivities, which we interpret in terms of surface disordering.