Nature of Slow Electron Diffraction by Crystals

Abstract

By making use of a new slow-electron diffraction apparatus of display type which is provided with the freedom of changing the glancing and azimuthal angles of the crystal and enables the pattern observation over a wide range of scattering angle by using cylindrical accelerating grids and fluorescent screen, the general feature of diffraction patterns from the cleavage surface of zincblende is studied with electrons in the energy range from 90 V to 500 V. A number of diffraction effects which are to be ascribed to the interactions among simultaneously excited reflexions are revealed. Since it would undoubtedly be necessary to use the dynamical theory of diffraction for explaining them, the way of approach to the slow electron diffraction phenomena with this theory and also the speciality of this theory for slow electrons are discussed from a general point of view, referring to observation of the high-energy electron diffraction from the same crystal surface. In particular, the conception of the penetration depth and the absorption effect of slow electrons in the crystal are critically discussed.