Channelling effects in atomic resolution STEM

C. J. Rossouw, Leslie J Allen, S. D. Findlay, M. P. Oxley

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51 Citations (Scopus)

Abstract

A Bloch wave theory for incoherent scattering of an incident plane wave has proved successful in predicting the fine detail in 2-D zone axis channelling patterns formed by ADF, BSE and characteristic X-ray detection in beam rocking mode. A previously published example of polarity determination of GaAs by channelling contrast is compared with simulations in order to illustrate the applicability of the theory. Modification of boundary conditions for a focused coherent probe allows lattice-resolution incoherent contrast based on ADF and EELS detection as well as X-ray emissions to be catered for within a similar theoretical framework. Mixed dynamic form factors constitute an integral part of this theory, where quantum-mechanical phase is a core issue. Simulations of lattice-resolution ADF and EELS are discussed with reference to various zone axis projections of GaAs. Issues of single versus double channelling conditions, and local versus nonlocal interactions, are discussed in relation to X-ray, ADF and EELS detection.

Original languageEnglish
Pages (from-to)299-312
Number of pages14
JournalUltramicroscopy
Volume96
Issue number3-4
DOIs
Publication statusPublished - 1 Jan 2003

Keywords

  • Boundary conditions
  • Coherent electron probe
  • Incoherent contrast
  • Lattice-resolution
  • Mixed dynamic form factor
  • Nonlocal interactions
  • STEM

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