High-resolution low-energy electron-diffraction analysis of the Pb(110) roughening transition

Abstract

We present a detailed line-shape analysis of the high-resolution low-energy electron-diffraction angular profiles measured from the Pb(110) surface undergoing a roughening transition. Experimentally, we show that the effects of multiple scattering and the thermal diffuse scattering do not make significant contributions to the line shape and therefore do not affect the structural information extracted from the angular intensity distribution of the diffracted beams associated with a surface undergoing the roughening transition. We have measured the effect of anisotropy in the roughening of a low-index plane metal surface. For the Pb(110) surface, the ratio of anisotropic interaction energies is estimated from the measurement to be ${\mathit{J}}_{\mathit{x}}$:${\mathit{J}}_{\mathit{y}}$=3.46:1. In addition, we have also measured an enhanced surface anharmonicity starting around 380 K, which is closely related to the anomalous derelaxation of the top layers previously observed by the high-energy ion-channeling technique. This derelaxation may be the major cause for the roughening transition occurring in the Pb(110) surface.