Structure and dynamics of periodic and randomly distributed surface features by high resolution helium atom scattering

Abstract

The scattering of helium atoms from surfaces has recently been methodically improved so as to make feasible new, high resolution studies of surface structures and vibrations. Examples are presented on structural studies of Au(111) reconstruction which reveal structures with a lattice spacing of 64 Å and provide evidence for soliton domain walls. Other experiments on rare gas physisorbed layers show new buckling structures of the overlayers. Inelastic scattering from clean surfaces yields information on surface phonon dispersion curves, and this is illustrated by two recent studies of the Pt(111) and Si(111) 2×1 clean surfaces and of physisorbed rare gases on a Pt(111) surface. Other new experiments measure the size and structure of single defects (adsorbed molecules and steps) on an atomic scale from the observed interference patterns. Finally the use of helium atom scattering to detect low frequency adsorbate vibrations in the meV range is illustrated for chemisorbed CO molecules on Pt(111).