Automatic software correction of residual aberrations in reconstructed HRTEM exit waves of crystalline samples

Abstract

We develop an automatic and objective method to measure and correct residual aberrations in atomic-resolution HRTEM complex exit waves for crystalline samples aligned along a low-index zone axis. Our method uses the approximate rotational point symmetry of a column of atoms or single atom to iteratively calculate a best-fit numerical phase plate for this symmetry condition, and does not require information about the sample thickness or precise structure. We apply our method to two experimental focal series reconstructions, imaging a β-Si3N4 wedge with O and N doping, and a single-layer graphene grain boundary. We use peak and lattice fitting to evaluate the precision of the corrected exit waves. We also apply our method to the exit wave of a Si wedge retrieved by off-axis electron holography. In all cases, the software correction of the residual aberration function improves the accuracy of the measured exit waves.

Tracking the sliding of grain boundaries at the atomic scale

“…To resolve the unit events of GB sliding more clearly than is possible through visual inspection, we developed an automated atom-column tracking method based on previous related studies (29)(30)(31)(32). This method can automatically label atom-columns and thus correlate them between images during GB sliding (fig.…”

Deep Learning Segmentation of Complex Features in Atomic-Resolution Phase-Contrast Transmission Electron Microscopy Images

“…The majority of graphene HRTEM images utilized in the current study are published along with the measured atomic coordinates in a previous study (Ophus et al, 2015). Some additional HRTEM images, including those from time- and focal-series are from various studies of the structure of graphene grain boundaries (Rasool et al, 2013, 2014; Ophus et al, 2017), were also included in the image dataset. All of our HRTEM images of graphene were recorded on the TEAM 0.5 microscope, a monochromated and aberration-corrected FEI/Thermo Fisher Titan microscope operated at 80 kV.…”

Aberration-corrected STEM imaging of 2D materials: Artifacts and practical applications of threefold astigmatism

“…In particular, the residual aberrations (especially aberrations with the same symmetry as the structure being imaged) can lead to contrast artifacts as a result of the probe "tails" to the intensity recorded at the nominal probe position (18)(19)(20). This profound effect of residual aberrations on HR-TEM imaging is also discussed in a number of publications (12,13,(21)(22)(23). However, most of these studies, both for HR-TEM and HR-STEM, predominately focused on graphene, a monolayer of carbon atoms exclusively.…”