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Crystal orientation; Electron diffraction; Electrons; High level languages; High resolution transmission electron microscopy; Mapping; Nanocrystalline materials; Nanocrystals; Python; Scanning electron microscopy; Template matching, Brute-force approach; CPU cores; Graphical processing unit acceleration; Graphical processing units; Multi-cores; Nanobeam electron diffraction; Open-source; Orientation mapping; Precession electron diffractions; Scanning transmission electron microscopy, Graphics processing unit, nanocrystal, acceleration; Article; crystal; data visualization; ecosystem; electron diffraction; four-dimensional imaging; graphical processing unit; image processing; open source software; performance; precipitation; reliability; reproducibility; scanning transmission electron microscopy; validation process; velocity
Abstract:
This work presents the new template matching capabilities implemented in Pyxem, an open source Python library for analyzing four-dimensional scanning transmission electron microscopy (4D-STEM) data. Template matching is a brute force approach for deriving local crystal orientations. It works by comparing a library of simulated diffraction patterns to experimental patterns collected with nano-beam and precession electron diffraction (NBED and PED). This is a computationally demanding task, therefore the implementation combines efficiency and scalability by utilizing multiple CPU cores or a graphical processing unit (GPU). The code is built on top of the scientific Python ecosystem, and is designed to support custom and reproducible workflows that combine the image processing, template library generation, indexation and visualization all in one environment. The tools are agnostic to file size and format, which is significant in light of the increased adoption of pixelated detectors from different manufacturers. This paper details the implementation and validation of the method. The method is illustrated by calculating orientation maps of nanocrystalline materials and precipitates embedded in a crystalline matrix. The combination of speed and flexibility opens the door for automated parameter studies and real-time on-line orientation mapping inside the TEM. © 2022 The Authors
