DIFFUSE REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION

A numerically manageable formalism for the dynamical calculation of diffuse reflection high-energy electron diffraction (RHEED) is presented. The diffuse scattering arises from transitions between dynamically calculated scattering states in the periodic part of the scattering potential and the nonperiodic part is treated as a perturbation. For atoms placed on equivalent lattice sites relative to the periodic-potential part, the formalism allows us to treat disorder scattering by kinematical structure factors that have to be multiplied by dynamically calculated atomic-scattering amplitudes so that the statistics of the disorder can be treated independently of the dynamical calculations. It is shown that azimuthal reflection profiles (parallel to the shadow edge) can, in favorable cases, be interpreted kinematically whereas polar profiles (normal to the shadow edge) are strongly influenced dynamically. It is further demonstrated by model calculations for the diffuse RHEED from disordered adsorbate layers that the corresponding broad scattering distribution depends strongly on the position of the adsorbate relative to the substrate. This should enable the use of RHEED in the field of structure analysis of disordered adsorbate layers. Finally, our concept is applied to thermal diffuse scattering. We show that the main structures of a measured broad thermal-diffuse-scattering distribution from Pt(110) can be explained with the Einstein model, i.e., independent atomic oscillations.