Dislocation contrast in electron channelling contrast images as projections of strain-like components. (2018)

• Record Type: Journal Article
• Authors: Pascal, E.; Hourahine, B.; Naresh-Kumar, G.; Mingard, K.; Trager-Cowan, C.
• Is Part Of: Materials today. Volume 5:Number 6(2018)Part 3
• Page Start: 14652
• Page End: 14661
• Publication Date: 2018
• Subjects: Electron channelling contrast imaging (ECCI) -- Dislocations -- Scanning electron microscope (SEM) -- Image simulation -- Defect imaging; Materials science -- Congresses -- Periodicals; 620.1
• DOI: 10.1016/j.matpr.2018.03.057
• Languages: English
• ISSNs: 2214-7853

Abstract

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" to 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 distinct 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 conditions.