Superstructures of oxygen and sulphur on a Fe(110) surface via fast atom diffraction

Abstract

Fast helium atoms and hydrogen molecules with energies from 400 eV up to several keV are grazingly scattered from a Fe(110) surface covered by oxygen and sulphur atoms forming $c(2\ifmmode\times\else\texttimes\fi{}2)$ and $c(1\ifmmode\times\else\texttimes\fi{}3)$ superstructures, respectively. For scattering along low-index azimuthal directions we observe defined diffraction patterns in the angular distributions for scattered projectiles. From the evaluation of those diffraction patterns we derive the widths of low-indexed axial channels, the corrugation of the interaction potential across these channels, and the normal positions of adsorbed atoms above the Fe lattice. Our analysis is based on semiclassical models using hard-wall approximation as well as individual potentials for the interaction of projectiles with the surface. By comparing the results of different models, we discuss the robustness of the information on the geometrical structure of the surfaces.