Energy Dependence of Extinction Distance and Transmissive Power for Electron Waves in Crystals

Abstract

Quantitative measurements of the energy dependence of the extinction distance and transmissive power for electron waves in crystals have been carried out photographically and electrically with 100-kV and 300-kV electron microscopes. The observations show that the relativistic correction for the mass of the electron must not be disregarded in the dynamical theory of electron diffraction for either the elastic or inelastic scattering. The energy dependence of the visibility of thickness extinction contour fringes and the resolutions of the images of thick films are also discussed. Some of the features observed in electron micrographs of thin metallic films taken at 250–300 kV are illustrated.