Competitive mechanisms contribute to image contrast from dislocations in annular dark field scanning transmission electron microscopy ADF STEM. A clear theoretical understanding of the mechanisms underlying the ADF STEM contrast is therefore essential for correct interpretation of dislocation images. This paper reports on a systematic study of the ADF STEM contrast from dislocations in a GaN specimen, both experimentally and computationally. Systematic experimental ADF STEM images of the edge character dislocations revealed a number of characteristic contrast features that are shown to depend on both the angular detection range and specific position of the dislocation in the sample. A theoretical model based on electron channelling and Bloch wave scattering theories, supported by multislice simulations using Grillo s strain channelling equation, is proposed to elucidate the physical origin of such complex contrast phenomena.
@article{arxiv.2005.10093,
title = {Insights into image contrast from dislocations in ADF-STEM},
author = {E. Oveisi and M. C. Spadaro and E. Rotunno and V. Grillo and C. Hebert},
journal= {arXiv preprint arXiv:2005.10093},
year = {2020}
}