Electron Microscopic Images of Lattice Imperfections

Abstract

Image formation of lattice imperfection in an electron microscope is studied theoretically. The treatment is an extension of the dynamical theory of electron diffraction for perfect crystal. The electron after passing through an imperfect crystal diverges due to inhomogeneous lattice distortion around the imperfection. Taking account of this effect the wave function of electron in the crystal is expressed approximately by a superposition of many plane waves. General expressions for the wave function and the intensity distribution of electron on the exit surface of the imperfect crystal are calculated as the functions of lattice displacement.
Examples of numerical calculation are given on the electron-micrographs of dislocation in ordinary bright field images and in moiré fringes.