Measurement of crystal parameters on backscatter Kikuchi diffraction patterns

Electron backscatter Kikuchi diffraction patterns (BKDPs) recorded in the scanning electron microscope (SEM) require measurements on the plane of the photographic film or on the recording screen. The para meters that require measurements are the equivalent electron source point on the pattern, or pattern centre, specimen-to-film distance, true interzonal angles, true interplanar angles, Bragg angles, and interplanar spacing. In this payer, the geometry and the methods of calculation of these parameters on BKDPs recorded directly on film are described in detail. The methods described are suitable for practical purposes, providing speed of calculation but limited accuracy. The inherent factors that limit the accuracy of any measurements on BKDPs are the limitations of the gnomonic projection, resulting in projected distortions in Kikuchi bands and diffuseness of Kikuchi band edges originating from inelastic scattering of electrons. The methods described are applied to crystallographic analysis of BKDPs recorded from silicon and polycrystalline copper.