Refinement of the 200 structure factor for GaAs using parallel and convergent beam electron nanodiffraction data

Knut Müller, Marco Schowalter, Jacob Jansen, Kenji Tsuda, John Titantah, Dirk Lamoen, Andreas Rosenauer

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

We present a new method to measure structure factors from electron spot diffraction patterns recorded under almost parallel illumination in transmission electron microscopes. Bloch wave refinement routines have been developed to refine the crystal thickness, its orientation and structure factors by comparison of experimentally recorded and calculated intensities. Our method requires a modicum of computational effort, making it suitable for contemporary personal computers. Frozen lattice and Bloch wave simulations of GaAs diffraction patterns are used to derive optimised experimental conditions. Systematic errors are estimated from the application of the method to simulated diffraction patterns and rules for the recognition of physically reasonable initial refinement conditions are derived. The method is applied to the measurement of the 200 structure factor for GaAs. We found that the influence of inelastically scattered electrons is negligible. Additionally, we measured the 200 structure factor from zero loss filtered two-dimensional convergent beam electron diffraction patterns. The precision of both methods is found to be comparable and the results agree well with each other. A deviation of more than 20% from isolated atom scattering data is observed, whereas close agreement is found with structure factors obtained from density functional theory [A. Rosenauer, M. Schowalter, F. Glas, D. Lamoen, Phys. Rev. B 72 (2005), 085326-1], which account for the redistribution of electrons due to chemical bonding via modified atomic scattering amplitudes.

Original languageEnglish
Pages (from-to)802-814
Number of pages13
JournalUltramicroscopy
Volume109
Issue number7
DOIs
Publication statusPublished - 2009 Jun

Keywords

  • Bonding
  • Convergent beam electron diffraction
  • GaAs
  • Parallel beam electron diffraction
  • Structure factor refinement

ASJC Scopus subject areas

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

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