Modelling fine-sliced three dimensional electron diffraction data with dynamical Bloch-wave simulations

Abstract

Recent interest in structure solution and refinement using electron diffraction (ED) has been fuelled by its inherent advantages when applied to crystals of sub-micron size, as well as a better sensitivity to light elements. Currently, data is often processed using software written for X-ray diffraction, using the kinematic theory of diffraction to generate model intensities -- despite the inherent differences in diffraction processes in ED. Here, we use dynamical Bloch-wave simulations to model continuous rotation electron diffraction data, collected with a fine angular resolution (crystal orientations of $\sim0.1^\circ$). This fine-sliced data allows us to reexamine the corrections applied to ED data. We propose a new method for optimising crystal orientation, and take into account the angular range of the incident beam and varying slew rate. We extract observed integrated intensities and perform accurate comparisons with simulations using rocking curves for a (110) lamella of silicon 185~nm in thickness. $R_1$ is reduced from $26\%$ with the kinematic model to $6.8\%$ using dynamical simulations.