Emittance minimization for aberration correction II: Physics-informed Bayesian optimization of an electron microscope.

Journal: Ultramicroscopy
Published Date:

Abstract

Aberration-corrected Scanning Transmission Electron Microscopy (STEM) has become an essential tool in understanding materials at the atomic scale. However, tuning the aberration corrector to produce a sub-Ångström probe is a complex and time-costly procedure, largely due to the difficulty of precisely measuring the optical state of the system. When measurements are both costly and noisy, Bayesian methods provide rapid and efficient optimization. To this end, we develop a Bayesian approach to fully automate the process by minimizing a new quality metric, beam emittance, which is shown to be equivalent to performing aberration correction. In part I, we derived several important properties of the beam emittance metric and trained a deep neural network to predict beam emittance growth from a single Ronchigram. Here we use this as the black box function for Bayesian optimization and demonstrate automated tuning of simulated and real electron microscopes. We explore different surrogate functions for the Bayesian optimizer and implement a deep neural network kernel to effectively learn the interactions between different control channels without the need to explicitly measure a full set of aberration coefficients. Both simulation and experimental results show the proposed method outperforms conventional approaches by achieving a better optical state with a higher convergence rate.

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.

Keywords

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