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122 results

Page 1 of 7

  • Analysis of Interpretable Data Representations for 4D-STEM Using Unsupervised Learning

  • Alexandra Bruefach, Colin Ophus, Mary C. Scott
  • Journal:
    Microscopy and Microanalysis / Volume 28 / Issue 6 / December 2022
    Published online by Cambridge University Press:
    08 September 2022, pp. 1998-2008
    Print publication:
    December 2022

  • Understanding the structure of materials is crucial for engineering devices and materials with enhanced performance. Four-dimensional scanning transmission electron microscopy (4D-STEM) is capable of mapping nanometer-scale local crystallographic structure over micron-scale field of views. However, 4D-STEM datasets can contain tens of thousands of images from a wide variety of material structures, making it difficult to automate detection and classification of structures. Traditional automated analysis pipelines for 4D-STEM focus on supervised approaches, which require prior knowledge of the material structure and cannot describe anomalous or deviant structures. In this article, a pipeline for engineering 4D-STEM feature representations for unsupervised clustering using non-negative matrix factorization (NMF) is introduced. Each feature is evaluated using NMF and results are presented for both simulated and experimental data. It is shown that some data representations more reliably identify overlapping grains. Additionally, real space refinement is applied to identify spatially distinct sample regions, allowing for size and shape analysis to be performed. This work lays the foundation for improved analysis of nanoscale structural features in materials that deviate from expected crystallographic arrangement using 4D-STEM.

  • Automated Design of Electron Mirrors for Multipass Electron Microscopy and 4D-STEM+EELS

  • Tyler Harvey, Colin Ophus
  • Journal:
    Microscopy and Microanalysis / Volume 28 / Issue S1 / August 2022
    Published online by Cambridge University Press:
    22 July 2022, pp. 3084-3085
    Print publication:
    August 2022
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