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

Normal-incidence, multiple-energy Kikuchi electron diffraction patterns (ho lograms) have been measured for clean GaAs(001) surface and for thin NaCl f ilms epitaxially grown on a GaAs(001) substrate. Three-dimensional atomic i mages of both structures have been obtained directly by the integral-energy phase-summing method. For the clean semiconductor surface, the superimpose d 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 af ter the deposition of the epitaxial NaCl film. Possible models of the NaCl/ GaAs(001) epitaxy are discussed. A detailed analysis of the reconstructed d iffraction patterns revealed that an initial formation of the Cl-Ga bond oc curred 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.