Oveisi, E.Spadaro, M. C.Rotunno, E.Grillo, VHebert, C.2019-06-182019-06-182019-06-182019-05-0110.1016/j.ultramic.2019.02.004https://infoscience.epfl.ch/handle/20.500.14299/157660WOS:000465417500019Competitive 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 reveal 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 numerical simulations based on Grillo's strain-channelling equation, is proposed to elucidate the physical origin of such complex contrast phenomena.MicroscopyMicroscopyadf-stemdislocation contrastelectron channellingbloch-wave scattering theorygrillo's strain-channelling equationelectron-microscopysoftware tooldetectorcelltext::journal::journal article::research article