Electron backscatter diffraction beyond the mainstream

Abstract

We present special applications of electron backscatter diffraction (EBSD) which aim to overcome some of the limitations of this technique as it is currently applied in the scanning electron microscope. We stress that the raw EBSD signal carries additional information which is useful beyond the conventional orientation determination. The background signal underlying the backscattered Kikuchi diffraction (BKD) patterns reflects the chemical composition and surface topography but also contains channeling-in information which is used for qualitative real-time orientation imaging using various backscattered electron signals. A significantly improved orientation precision can be achieved when dynamically simulated pattern are matched to the experimental BKD patterns. The breaking of Friedel's rule makes it possible to obtain orientation mappings with respect to the point-group symmetries. Finally, we discuss the determination of lattice parameters from individual BKD patterns. Subgrain structure in a single quartz grain. The increased noise level in the left map reflects the lower precision of a standard orientation determination using band detection by the Hough transform. The right map results from the same experimental raw data after orientation refinement using a pattern matching approach. The colors correspond an adapted inverse pole figure color key with a maximum angular deviation of about 2 • from the mean orientation.

Improving EBSD precision by orientation refinement with full pattern matching

“…The pattern matching approach we applied is described in detail in references (Nolze et al ., 2016) and (Nolze et al ., 2018). In brief, each experimentally observed Kikuchi pattern is compared with simulated patterns which are reprojected according to the varying parameters of the crystal orientation and the fixed parameters of the projection geometry.…”

“…A dictionary approach to matching simulated patterns to acquired patterns has been reported to improve phase discrimination (Ram & De Graef, 2018) and suggests a reduction in orientation noise (Chen et al ., 2015). Orientation refinement by full pattern matching (FPM) of simulated to measured EBSPs (Nolze et al ., 2016; Nolze et al ., 2018) has been shown to improve angular resolution from the reduction in noise and improved identification of sub grains in quartzite, with an approximate improvement of precision by a factor of 3. This method has been applied to silicon crystals in a separate study (Friedrich et al ., 2018), where as a measure of angular resolution the 95th percentile of the KAM angle distribution was obtained at 0.06° (Friedrich et al ., 2018).…”

“…This work presents further use of the refinement by pattern matching (Nolze et al ., 2016) to demonstrate improvement in angular precision by about an order of magnitude compared to orientation data delivered by the EBSD system software. In particular, the features revealed by this improved precision are shown to be dislocations by comparison with high resolution ECCI and it is shown that it is possible to quantify the misorientations around such features.…”

GGR Biennial Critical Review: Analytical Developments Since 2014

“…The raw EBSD signal carries information, not only related to orientation but also related to composition, topography and channelling‐in effects (e.g., Nolze et al . ). By saving individual EBSPs, we can work with the data ‘offline’, meaning that the instrumentation does not need to reprocess the data during analysis.…”

“…As an example, electron backscatter (BSE) images obtained from post‐processing raw EBSD data are better than BSE images obtained directly from a proper BSE detector (Nolze et al . ). This is because the backscatter signal obtained from raw EBSD data typically has a longer dwell time per pixel, a larger solid angle and energy filtering from aluminium‐coated phosphor screen.…”