Holographic inversion of Kikuchi electron diffraction patterns for thin epitaxial NaCl films grown on GaAs(001)

Normal-incidence, multiple-energy Kikuchi electron diffraction patterns (holograms) have been measured for clean GaAs(001) surface and for thin NaCl films epitaxially grown on a GaAs(001) substrate. Three-dimensional atomic images of both structures have been obtained directly by the integral-energy phase-summing method. For the clean semiconductor surface, the superimposed images of Ga and As bulk atoms were well resolved within an accuracy of 0.5 Angstrom. A distinctly different local atomic configuration was found after the deposition of the epitaxial NaCl film. Possible models of the NaCl/GaAs(001) epitaxy are discussed. A detailed analysis of the reconstructed diffraction patterns revealed that an initial formation of the Cl-Ga bond occurred in the system, and after deposition of 5 ML NaCl, the substrate was uniformly covered by a layer at least 3 ML thick. (C) 1999 Elsevier Science B.V. All rights reserved.