Identification of Kikuchi lines in electron diffraction patterns collected in small-angle geometry.

Abstract

It is demonstrated that Kikuchi features become clearly visible if reflection high-energy electron diffraction (RHEED) patterns are filtered using digital image processing software. The results of such pattern transformations are shown for SrTiO₃ with mixed surface termination for data collected at different azimuths of the incident electron beam. A simplified analytical approach for the theoretical description of filtered Kikuchi patterns is proposed and discussed. Some examples of raw and filtered patterns for thin films are shown. RHEED patterns may be treated as a result of coherent and incoherent scattering of electron waves. The effects of coherent scattering may be considered as those occurring due to wave diffraction by an idealized crystal and, usually, only effects of this type are analysed to obtain structural information on samples investigated with the use of RHEED. However, some incoherent scattering effects mostly caused by thermal vibrations of atoms, known as Kikuchi effects, may also be a source of valuable information on the arrangements of atoms near the surface. Typically, for the case of RHEED, Kikuchi features are hidden in the intensity background and researchers cannot easily recognize them. In this paper, it is shown that the visibility of features of this type can be substantially enhanced using computer graphics methods.