Precision controlled atomic resolution scanning transmission electron microscopy using spiral scan pathways

Abstract

Atomic-resolution imaging in an aberration-corrected scanning transmission electron microscope (STEM) can enable direct correlation between atomic structure and materials functionality. The fast and precise control of the STEM probe is, however, challenging because the true beam location deviates from the assigned location depending on the properties of the deflectors. To reduce these deviations, i.e. image distortions, we use spiral scanning paths, allowing precise control of a sub-Å sized electron probe within an aberration-corrected STEM. Although spiral scanning avoids the sudden changes in the beam location (fly-back distortion) present in conventional raster scans, it is not distortion-free. “Archimedean” spirals, with a constant angular frequency within each scan, are used to determine the characteristic response at different frequencies. We then show that such characteristic functions can be used to correct image distortions present in more complicated constant linear velocity spirals, where the frequency varies within each scan. Through the combined application of constant linear velocity scanning and beam path corrections, spiral scan images are shown to exhibit less scan distortion than conventional raster scan images. The methodology presented here will be useful for in situ STEM imaging at higher temporal resolution and for imaging beam sensitive materials.

Imaging Secondary Electron Emission from a Single Atomic Layer

“…To put the SEEBIC signal onto a more quantitative footing we leveraged the previously developed G‐STEM platform [ 49,50 ] to interface with the STEM scan coils and TIA, synchronize the signals, and preserve the absolute TIA output. This amounts to reproducing the output of the previous experiment but bypasses the unknown digitization of the Digital Micrograph system so that the TIA output can be recorded directly.…”

Design Considerations for Discrete Frequency Infrared Microscopy Systems

“…226,227 Nonoptical-based distortions can also arise in stage-scanning modalities, when the true stage position does not match the target position at a precise time, because of mechanical uncertainties such as drift, instability, or fly-back. 228,229 Finally, in hyperspectral imaging systems that operate over a wide spectral range, some aberrations reflect a large variation in the imaging performance of the system. Hence, it is important to characterize the system aberrations as a function of wavenumber.…”

Advances and Applications of Atomic-Resolution Scanning Transmission Electron Microscopy

“…Alternative scanning paths to form images may be used to reduce image distortions. Spiral scanning paths were investigated as an alternative approach to acquiring images at extremely high speed (Sang et al, 2016(Sang et al, , 2017. Different scans with constant angular and linear velocity spirals were evaluated.…”