Coherence and multiple scattering in "Z-contrast" images

M. M.J. Treacy, J. M. Gibson

Research output: Contribution to journalArticle

92 Scopus citations

Abstract

Hollow-cone dark-field images from crystalline silicon were examined as a function of thickness and scattering angle. We find that both coherent scattering and multiple scattering can cause the intensity to depend non-linearly on thickness, even for high-angle scattering events. A simple method for estimating the effect of multiple elastic scattering in thick specimens is provided. We show theoretically, that a coherence volume exists around each scatterer whose dimensions depend inversely on scattering angle. The coherence volume has a narrow "cigar" shape, elongated along the optic axis. The narrowness ensures that inter-atomic-column interferences, such as zero-order Laue zone Bragg reflections, are suppressed, whereas the elongation permits intra-atomic-column interference (or columnar diffraction). In high-resolution "Z-contrast" images, this bias towards columnar diffraction acts to enhance the signal from atom columns.

Original languageEnglish (US)
Pages (from-to)31-53
Number of pages23
JournalUltramicroscopy
Volume52
Issue number1
DOIs
StatePublished - Sep 1993
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Instrumentation

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