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We demonstrate an approach to overcome Kikuchi pattern misindexing problems caused by crystallographic pseudosymmetry in electron backscatter diffraction (EBSD) measurements. Based on the quantitative comparison of experimentally measured Kikuchi patterns with dynamical electron diffraction simulations, the algorithm identifies the best-fit orientation from a set of pseudosymmetric candidates. Using measurements on framboidal pyrite (FeS2) as an example, we also show the improvement of the orientation precision using this approach.
A pseudosymmetric description of the crystal lattice derived from a single wideangle Kikuchi pattern can have several causes. The small size (<15%) of the sector covered by an electron backscatter diffraction pattern, the limited precision of the projection centre position and the Kikuchi band definition are crucial. Inherent pseudosymmetries of the crystal lattice and/or structure also pose a challenge in the analysis of Kikuchi patterns. To eliminate experimental errors as much as possible, simulated Kikuchi patterns of 350 phases have been analysed using the software CALM [Nolze et al. (2021). J. Appl. Cryst. 54, 1012–1022] in order to estimate the frequency of and reasons for pseudosymmetric crystal lattice descriptions. Misinterpretations occur in particular when the atomic scattering factors of non-equivalent positions are too similar and reciprocal-lattice points are systematically missing. As an example, a pseudosymmetry prediction depending on the elements involved is discussed for binary AB compounds with B1 and B2 structure types. However, since this is impossible for more complicated phases, this approach cannot be directly applied to compounds of arbitrary composition and structure.
The tetragonal crystal- structure type of chalcopyrites (chemical formula AIBIIICVI2) is a superstructure of sphalerite type. The c/a ratio differs generally from the ideal value 2, i.e., the crystal structure is pseudocubically distorted. For CuInSe2 and CuGaSe2 thin films, simulations demonstrate that it is theoretically possible to reveal the tetragonality in electron backscatter-diffraction (EBSD) patterns for CuGaSe2, whereas it may not be possible for CuInSe2. EBSD experiments on CuGaSe2 thin films using the ”Advanced Fit” band-detection method show that it is possible to extract accurate misorientation-angle distributions from the CuGaSe2 thin film. Pole figures revealing the texture of the CuGaSe2 thin film are shown, which agree well with X-ray texture measurements from the same layer.