Diffraction Contrast Effect of Electrons Scattered Inelastically through Large Angles

The electron microscopic image formed by electrons scattered through large angle gives well resolved fringes at stacking faults. The spacing of these fringes near the entrance surface depends on the Bragg condition of the incident electron, while that near the exit surface depends on the Bragg condition of electrons which form the image. The contrast of the fringe formed by large angle scattering is opposite to that by small angle scattering. The contrast reversal is interpreted qualitatively by the dynamical theory of electron diffraction. The contrast loss observed in ordinary images for thick crystals is also discussed.