Back Reflected Intensity for the Laue Case

Abstract

The exact formulation of the dispersion equation in the dynamical electron diffraction theory of Bethe leads to the existence of four wave fields in the crystal in the two-beam Laue case. At low energies it is necessary to consider all four wave fields within the crystal and the resulting interferences between them. Computer calculations for the vacuum electron currents in the exact two-beam case of low energy electron diffraction for a thin parallel slab are shown. The current variation due to interferences between all the crystal wave fields for the elastic case and for the case where absorption is introduced by means of a complex Fourier coefficient of the potential are demonstrated. The importance of the structure due to the additional solutions for primary electron energies below 50 eV shows that any elastic theory of electron diffraction must contain the total wave field to be valid at these low energies.