MODELS FOR TERMINATION OF CRYSTAL BOUNDARIES IN THE THEORY OF TRANSMISSION ELECTRON-DIFFRACTION AND COMPARISON WITH EXPERIMENTAL-DATA

Calculations of electron diffraction intensities in transmission electron microscopy commonly assume a model representing surfaces and interfaces in crystals as flat boundaries (flat-boundary model, FBM). It is shown that the independent-atom model (IAM) representing the crystal potential as a superposition of spherical atomic potentials leads to improved boundary conditions. Intensities calculated from the two models at large deviation from the Bragg peak in weak reflections (e.g. 200 in InGaAs) differ significantly. Results from both types of calculation are compared with an experimental diffraction pattern recorded using energy-filtered large-angle convergent-beam electron diffraction from an In0.53Ga0.47/InP bicrystal. It is shown that calculations using the IAM give a better agreement with experiment.