Reflection high energy diffraction by the Ag(001), Ag(110) and Ag(111) surfaces

Abstract

Elastic reflection high energy electron diffraction (RHEED) by the Ag(001), Ag(110) and Ag(111) surfaces is studied with the aid of model calculations of the RHEED intensities. The electron energies are taken to be in the range 10–40 keV and the incident beam azimuth is taken to be in a direction of high symmetry. The calculations are based on the use of a dynamical diffraction theory in which the electrons are taken to be diffracted by a potential which is periodic in the two dimensions parallel to the surface but need not be periodic in the dimension perpendicular to the surface. The results of the calculations are presented in the form of rocking curves which illustrate how the diffracted beam intensities depend on the glancing angle of the incident beam. It is shown that the rocking curves have similar features to a typical set of LEED I–V plots: these are series of primary Bragg peaks, secondary Bragg peaks and resonance peaks. Many of the primary Bragg peaks are weak because the atomic layers parallel to the surface predominantly diffract electrons out of the incident beam. A consequence of this is that the secondary Bragg peaks are very pronounced. The procedure used to compute the RHEED intensities also gives the perpendicular dependence of the electron wave function and plots of the electron intensity as a function of depth into the crystal are used to explain the mechanisms causing the various peaks in the rocking curves.