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

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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.
Original languageEnglish
Pages (from-to)14652–14661
Number of pages10
JournalMaterials Today: Proceedings
Volume5
Issue numberIssue 6, Part 3
DOIs
Publication statusPublished - 12 Jun 2018

Fingerprint

image contrast
Diffraction
projection
Electrons
diffraction
electrons
Defects
defects
electron flux density
Forward scattering
Burgers vector
forward scattering
Dislocations (crystals)
Electron diffraction
wurtzite
Electron beams
acquisition
Electron microscopes
electron diffraction
electron microscopes

Keywords

  • electron channelling contrast imaging (ECCI)
  • dislocations
  • scanning electron microscope (SEM)
  • image simulation
  • defect imaging

Cite this

@article{61b9dc72cac54f788c4718b0ca62ee2f,
title = "Dislocation contrast in electron channelling contrast images as projections of strain-like components",
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.",
keywords = "electron channelling contrast imaging (ECCI), dislocations, scanning electron microscope (SEM), image simulation, defect imaging",
author = "E. Pascal and B. Hourahine and G. Naresh-Kumar and K. Mingard and C. Trager-Cowan",
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Dislocation contrast in electron channelling contrast images as projections of strain-like components. / Pascal, E.; Hourahine, B.; Naresh-Kumar, G.; Mingard, K.; Trager-Cowan, C.

In: Materials Today: Proceedings, Vol. 5, No. Issue 6, Part 3, 12.06.2018, p. 14652–14661.

Research output: Contribution to journalArticle

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AB - 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.

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