Recent Advances in Quantitative Convergent Beam Electron Diffraction

Two recent advances in quantitative convergent beam electron diffraction (CBED) developed at the University of Bristol are described in this paper. The first is a new scanning technique in which the diffracted intensities in the resulting pattern are integrated through the Bragg condition, equivalent to precessing the sample around a stationary beam. Many more reflections are excited than in a conventional diffraction pattern, excitation errors are removed and non-systematic dynamical interactions are reduced. This new technique is used for an ab-initio structure determination of Er2Ge207, the results of which are presented and compared to those from single crystal X-ray studies. The second technique is a method of making accurate bond (deformation) charge measurements for known structures by zone-axis CBED pattern matching. Results for Si [110] patterns obtained from a Hitachi HF2000 FEG-TEM with a Gatan Imaging Filter are discussed. These results are in excellent agreement with those obtained previously using the X-ray Pendelldsung technique.