EBSD Pattern Subtraction for Sub-100 nm Phase Separation
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Solution Overview
Problem
Current methods for processing Kikuchi diffraction patterns struggle to accurately separate overlapped signals from multiple crystals, limiting the resolution of microstructural features, especially for phases below 100 nm, and require challenging sample preparation and low-energy electron beam conditions.
Innovation Solution
A method involving the identification of target and template patterns, with modifications in contrast and intensity based on relative properties, followed by subtraction to extract secondary phase signals, and optionally using blind signal separation or FFT phase correlation to enhance signal separation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If low-keV EBSD (5 keV) is used to reduce electron-matter interaction volume, then finer microstructures can be analyzed, but sample preparation becomes challenging and Kikuchi band detection reliability decreases
Solution Approach 1:
The patent changes the electron beam energy parameter to standard EBSD energies (15-30 keV) instead of low-keV (5 keV), thereby maintaining easier sample preparation and more reliable Kikuchi band detection while still achieving fine microstructure analysis through signal separation methods
Solution Approach 2:
The patent extracts and separates the secondary phase signal from the overlapped diffraction pattern by identifying and removing the matrix signal contribution, allowing detection of fine microstructures without requiring reduced interaction volume
2Ease of operation
If standard EBSD is used to maintain ease of operation, then only a single predominant signal can be indexed, but fine-scale microstructural features are missed
Solution Approach 1:
The patent segments the overlapped diffraction pattern into multiple independent signal contributions from different crystals/phases by identifying individual pattern components, allowing multiple signals to be indexed from a single pattern while maintaining standard EBSD operation
Solution Approach 2:
The patent adds a signal separation dimension to the standard EBSD analysis by decomposing the diffraction pattern into multiple contributing signals, thereby enabling detection of fine-scale features without complicating the operational procedure
3Measurement precision
If Pattern Matching technique is used to separate overlapped signals, then up to three signals can be indexed, but the information is not spatially resolved
Solution Approach 1:
The patent applies signal separation locally to each individual diffraction pattern rather than globally across multiple patterns, thereby maintaining spatial resolution while separating overlapped signals from different phases
4Extent of automation
If Kikuchi band detection relies on Hough transform, then detection can be automated, but reliability decreases with decreasing electron energy
Solution Approach 1:
The patent changes the electron beam energy parameter back to standard EBSD energies (15-30 keV) where the Hough transform remains reliable and effective for automated Kikuchi band detection
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the accurate extraction of phases below 100 nm at standard EBSD incident energies, improving the resolution of microstructural features and adapting to different signal separation needs by utilizing standard sample preparation and pattern acquisition processes.
Implementation Method 1
Electron backscatter diffraction (EBSD) allows indexing multiple contributions in overlapped spot diffraction patterns
Implementation Method 2
separating the overlapped signals and then generating meaningful information from the separated signals
Data Source
AI summary
A set of methods of processing a set of Kikuchi diffraction patterns acquired for a series of incident positions of an electron beam on a sample material are described. One such method involves the steps of identifying a first pattern in the set containing a matrix signal and suspected of additionally containing a secondary phase signal; identifying a second pattern close to the first pattern which contains a matrix signal without containing a secondary phase signal; modifying the contrast and intensity of either the first pattern or the second pattern, the modification depending on a relative property of the first and second patterns, resulting in a modified first or second pattern; and obtaining a secondary phase signal pattern by either i) if the first pattern was modified, subtracting the original second pattern from the modified first pattern; or ii) if the second pattern was modified, subtracting the modified second pattern from the original first pattern.