Chapter

HIGH-RESOLUTION IMAGES OF CRYSTALS AND THEIR DEFECTS

JOHN C. H. SPENCE

in High-Resolution Electron Microscopy

Third edition

Published in print October 2008 | ISBN: 9780199552757
Published online January 2010 | e-ISBN: 9780191708664 | DOI: http://dx.doi.org/10.1093/acprof:oso/9780199552757.003.0005

Series: Monographs on the Physics and Chemistry of Materials

 HIGH-RESOLUTION IMAGES OF CRYSTALS AND THEIR DEFECTS

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This chapter introduces many-beam high-resolution imaging by first analysing in detail the case of two or three beams, and showing how aberrations may be arranged to cancel by using off-axis illumination (as later related to Ptychography). The phenomenon of Fourier or Talbot imaging is reviewed, and the images are shown to be periodic in some aberration coefficients. The manner in which a finite incident beam divergence limits depth of field is explained. The main results of kinematic, two-beam, and the charge-density approximations are given. The full multiple scattering theory is then given, symmetry reduction of the dispersion matrix reviewed, and discussions are provided of partial coherence with multiple scattering, absorption effects due to inelastic scattering with multiple scattering, dynamically forbidden reflections, and the relationship between the various formulations (and sign conventions) of high energy electron scattering theory. A case study of imaging in germanium is given, showing the masking effect of Fourier imaging on defects. The chapter ends with case studies from materials science — imaging dislocation kinks, complex oxides, minerals, quasicrystals, interfaces.

Keywords: multiple scattering; Talbot images; Fourier images; two-beam theory; kinematic theory; beam divergence; scattering matrix; Bloch waves; depth of focus; depth of field

Chapter.  25740 words.  Illustrated.

Subjects: Atomic, Molecular, and Optical Physics

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