INTERPRETATION OF SUBSTRATE PHOTOELECTRON DIFFRACTION

Azimuthal diffraction patterns of 1s and 2s photoelectrons, of plasmon-loss peaks and inelastic-background intensities, as well as of medium-energy electrons, are presented for polar angles of 45°and 55°off the surface normal of a clean Al(001) crystal. A comparison of such data is important for the assessment of two currently used models for describing electron diffraction: the short-range scattering-cluster approach and the Kikuchi or Bragg-scattering method. It is concluded that both methods are essentially equivalent. Differences in experimental diffraction patterns of elastically and inelastically scattered electrons can be related to different probing depths and, associated with it, different relative importance of multiple scattering. It is also found that photoelectron-diffraction patterns and medium-energy electron-diffraction patterns in the 1-keV regime are very similar, as long as the kinetic energies are not too different. From this it follows that substrate photoelectron-diffraction patterns can be more easily obtained by elastic electron scattering. © 1990 The American Physical Society.