Impact of dynamical scattering on quantitative contrast for aberration-corrected transmission electron microscope images |
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| Institution: | 1. School of Science, Southwest University of Science and Technology, Mianyang 621010, China;2. Department of Physics, Arizona State University, Tempe, AZ 85287, USA;1. University of Valle, Computer and Systems Engineering School, Cali, Colombia;2. University of León, Industrial and Informatics Engineering School, León, Spain;3. University of Valle, Morphology Department, Faculty of Health, Cali, Colombia;1. A.V. Zhirmunsky Institute of Marine Biology, FEB RAS, Vladivostok 690041, Russia;2. Far Eastern Federal University, Vladivostok 690950, Russia;3. Nematology Research Unit, Department of Biology, Ghent University, Belgium;1. School of Science, Faculty of Science and Engineering, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand;2. School of Engineering, Faculty of Science and Engineering, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand |
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| Abstract: | Aberration-corrected transmission electron microscope images taken under optimum-defocus conditions or processed offline can correctly reflect the projected crystal structure with atomic resolution. However, dynamical scattering, which will seriously influence image contrast, is still unavoidable. Here, the multislice image simulation approach was used to quantify the impact of dynamical scattering on the contrast of aberration-corrected images for a 3C-SiC specimen with changes in atomic occupancy and thickness. Optimum-defocus images with different spherical aberration (CS) coefficients, and structure images restored by deconvolution processing, were studied. The results show that atomic-column positions and the atomic occupancy for SiC ‘dumbbells’ can be determined by analysis of image contrast profiles only below a certain thickness limit. This limit is larger for optimum-defocus and restored structure images with negative CS coefficient than those with positive CS coefficient. The image contrast of C (or Si) atomic columns with specific atomic occupancy changes differently with increasing crystal thickness. Furthermore, contrast peaks for C atomic columns overlapping with neighboring peaks of Si atomic columns with varied Si atomic occupancy, which is enhanced with increasing crystal thickness, can be neglected in restored structure images, but the effect is substantial in optimum-defocus images. |
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| Keywords: | Aberration-corrected transmission electron microscopy Dynamical scattering Image contrast Atomic-column position Atomic occupancy |
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