Elimination of Substrate Scattering in Electron Diffraction

Abstract

Relative intensities of single crystalline electron diffraction spots can be calculated using n-beam dynamical electron diffraction theory. The scattering matrix formulation developed by Sturkey has been applied in this laboratory to calculate the relative intensities of 42 simultaneously diffracted beams from thin gold platelets. The calculations assume normal incidence, parallel entrance and exit surfaces of the crystal, and crystal thickness t. These assumptions severly restrict the experimental techniques which may be used to measure intensities. A suitable technique must hold the crystal normal to the incident beam, allow thickness measurements, and prevent bending. These rather stringent conditions are satisfied by mounting the microcrystal on a substrate. However, a substrate scatters the electron beam and alters the relative intensities being measured. To eliminate substrate scattering and to satisfy most of the above requirements the micro-crystals were studied through holes in the substrate.