Dislocation contrast in electron channelling contrast images as projections of strain-like components

Pascal, E. and Hourahine, B. and Naresh-Kumar, G. and Mingard, K. and Trager-Cowan, C. (2018) Dislocation contrast in electron channelling contrast images as projections of strain-like components. Materials Today: Proceedings, 5 (Issue ). 14652–14661. ISSN 2214-7853

[img]
Preview
Text (Pascal-etal-MTP-2017-Dislocation-contrast-in-electron-channeling-contrast-images)
Pascal_etal_MTP_2017_Dislocation_contrast_in_electron_channeling_contrast_images.pdf
Final Published Version
License: Creative Commons Attribution 4.0 logo

Download (1MB)| Preview

    Abstract

    The forward scattering geometry in the scanning electron microscope enables the acquisition of electron channelling contrast imaging (ECCI) micrographs. These images contain diffraction information from the beam of electrons “channelling in” into the sample. Since small, localised strains strongly affect the electron diffraction, defects which introduce lattice displacement in the region of the surface the electron beam is interacting with will be revealed as district variation in backscattered electron intensity. By acquiring multiple images from the same area in different diffraction conditions and comparing them against modelled predictions of defect strain sampled by diffraction, it is possible to characterise these defects. Here we discuss the relation between the elastic strain introduced by a threading dislocation intersecting the surface and the contrast features observed in the electron channelling contrast image of that region. Preliminary simulated channelling contrast images are shown for dislocations with known line direction and Burgers vectors using a two-beam dynamical diffraction model. These are demonstrated to be in qualitative agreement with measured images of dislocated polar wurtzite GaN acquired with two different diffraction condition.