Emittance minimization for aberration correction I: Aberration correction of an electron microscope without knowing the aberration coefficients.

Journal: Ultramicroscopy
Published Date:

Abstract

Precise alignment of the electron beam is critical for successful application of scanning transmission electron microscopes (STEM) to understanding materials at atomic level. Despite the success of aberration correctors, aberration correction is still a complex process. Here we approach aberration correction from the perspective of accelerator physics and show it is equivalent to minimizing the emittance growth of the beam, the span of the phase space distribution of the probe. We train a deep learning model to predict emittance growth from experimentally accessible Ronchigrams. Both simulation and experimental results show the model can capture the emittance variation with aberration coefficients accurately. We further demonstrate the model can act as a fast-executing function for the global optimization of the lens parameters. Our approach enables new ways to quickly quantify and automate aberration correction that takes advantage of the rapid measurements possible with high-speed electron cameras. In part II of the paper, we demonstrate how the emittance metric enables rapid online tuning of the aberration corrector using Bayesian optimization.

Authors

  • Desheng Ma
    School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA. Electronic address: dm852@cornell.edu.
  • Steven E Zeltmann
    Platform for the Accelerated Realization, Analysis, and Discovery of Interface Materials, Cornell University, Ithaca, New York 14853, United States.
  • Chenyu Zhang
    Academy of Clinical Medicine, Guizhou Medical University, Guiyang 550004, China.
  • Zhaslan Baraissov
    School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA.
  • Yu-Tsun Shao
    Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089, USA.
  • Cameron Duncan
    Department of Physics, Cornell University, Ithaca, NY 14853, USA.
  • Jared Maxson
    Department of Physics, Cornell University, Ithaca, NY 14853, USA.
  • Auralee Edelen
    SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA.
  • David A Muller
    School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA.

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