Measurement of crystal parameters on backscatter kikuchi diffraction patterns

Abstract

Summary: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 parameters 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 paper, 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.

Use of reciprocal lattice layer spacing in electron backscatter diffraction pattern analysis

“…We are aware of no studies that have attempted to make use of the HOLZ rings that are visible in EBSD patterns. There has been some speculation that the measurement of reciprocal lattice layer spacings should be possible, but the nature of the gnomonic projection may make this extremely difficult and tedious [5].…”

“…A newer use of EBSD is for the identification of unknown crystalline phases in bulk specimens [3,4]. It is for this application that the use of higher order Laue zone (HOLZ) rings to determine the reciprocal lattice layer spacing may be most helpful [5].…”

Investigation of HOLZ rings in EBSD patterns

“…It is also possible to distinguish between different previously selected crystallographic phases, see for example [5,6]. A further advantage is the high lateral resolution of up to 6 nm, which, in this case, could be achieved for a thin platinum film deposited on silicon [7].However, the accuracy in the lattice parameter determination obtained by measuring the width of Kikuchi bands is generally very low and at best only about 5% in dependence on the Kikuchi reflections used, sometimes only 10% [8]. Here, an improvement can allow the exploitation of the so-called HigherOrder Laue Zone (HOLZ) rings.…”

Application of Electron Backscatter Diffraction to Phase Identification

“…Given its diffraction-based origins, the EBSD technique can directly satisfy the structural determination component of phase identification, but not without limitations. The complete data set of structural information contained within an EBSD pattern is difficult to extract, typically requiring non-standard setups and/or detectors, and space group and lattice parameter determination by EBSD has only been accomplished with meticulous manual scrutiny of the EBSD diffraction patterns (Baba-Kishi and Dingley 1989, Baba-Kishi and Dingley 1989a, Baba-Kishi 1998, Michael and Eades, 2000.…”