Huang Shuoyuan, Francis Carter, Sunderland John, Jambur Vrishank, Szlufarska Izabela, Voyles Paul M
Department of Materials Science and Engineering, University of Wisconsin Madison, Madison, Wisconsin 53706, USA.
Department of Materials Science and Engineering, University of Wisconsin Madison, Madison, Wisconsin 53706, USA.
Ultramicroscopy. 2022 Nov;241:113612. doi: 10.1016/j.ultramic.2022.113612. Epub 2022 Sep 6.
Densely spaced four-dimensional scanning transmission electron microscopy (4D STEM) analyzed using correlation symmetry coefficients enables large area mapping of approximate rotational symmetries in amorphous materials. Here, we report the effects of Poisson noise, limited electron counts, probe coherence, reciprocal space sampling, and the probe-sample interaction volume on 4D STEM symmetry mapping experiments. These results lead to an experiment parameter envelope for high quality, high confidence 4D STEM symmetry mapping. We also establish a direct link between the symmetry coefficients and approximate rotational symmetries of nearest-neighbor atomic clusters using electron diffraction simulations from atomic models of a metallic glass. Experiments on a PdCuSi metallic glass thin film demonstrate the ability to image the types, sizes, volume fractions, and spatial correlations amongst local rotationally symmetry regions in the glass.
