Abstract
A raw electron backscatter diffraction (EBSD) signal can be empirically decomposed into a Kikuchi diffraction pattern and a smooth background. For pattern indexing, the latter is generally undesirable but can reveal topographical, compositional, or diffraction contrast. In this study, we proposed a new background correction method using polynomial fitting (PF) algorithm to obtain clear Kikuchi diffraction patterns for some applications in nonconductive materials due to coating problems, at low accelerated voltage and at rough sample surfaces and for the requirement of high pattern quality in HR-EBSD. To evaluate the quality metrics of the Kikuchi patterns, we initially used three indices, namely, pattern quality, Tenengrad variance, and spatial–spectral entropy-based quality to detect the clarity, contrast, and noise of Kikuchi patterns obtained at 5 and 15 kV. Then, we examined the performance of PF method by comparing it with pattern averaging and Fourier transform-based methods. Finally, this PF background correction is demonstrated to extract the background images from the blurred diffraction patterns of EBSD measurements at low kV accelerating voltage and with coating layer, and to provide clear Kikuchi patterns successfully.
Highlights
Background correction algorithm withpolynomial fitting (PF), pattern averaging (PA), and Fourier transform-based (FT) methods.After hitting the specimen surface, the primary beam electrons suffer random elastic and inelastic scattering due to energy lose
The quality metrics of the diffraction patterns are evaluated using pattern quality (PQ), Tenengrad variance (TenV), and SSEQ indices, which correspond to the clarity, high contrast, and high noise of the patterns, respectively
We propose a PF background correction method to extract background noise and diffraction pattern from raw diffraction patterns under low accelerated voltage or coated sample
Summary
After hitting the specimen surface, the primary beam electrons suffer random elastic and inelastic scattering due to energy lose. After a given penetration depth, the electrons scatter at various angles and some electrons diffract following the Bragg’s law, resulting in Kikuchi bands. A relatively low-intensity signal is superimposed with a dominating background signal, as observed on the detector[39]. To solve the problem of low signal-to-noise ratio in EBSD patterns, the background correction algorithm is generally used for the post-processing of EBSD patterns. We propose a PF background correction algorithm, as shown in Fig. 4: AHE contrast enhancement, background estimation, background subtraction, and contrast-limited adaptive histogram equalization (CLAHE) contrast enhancement
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