The Effect of Amorphous Surface Layers on Electron Microscope Images of Crystals

Abstract

By means of an energy selecting electron microscope (H. Watanabe: Japan. J. appl. Phys. 3 (1964) 480), energy analysis was carried out for the electrons forming a special dark-field image, which was obtained by shifting the objective aperture slightly from the optical axis (Y. Kamiya and R. Uyeda: J. Phys. Soc. Japan 16 (1961) 1361). In the no-loss image of aluminum, equal thickness fringes were observed and the intensity averaged over the period was proportional to that in 23 eV loss image which is characteristic to the surface layers. The small angle no-loss scattering by surface layer was concluded to have a major contribution to the no-loss special dark field image, contrasting to the conclusion by Castaing et al. (C.R. Acad. Sci. (Paris), 262 (1966) 1051) that the thermal scattering plays the role. In case of magnesium oxide a definite conclusion was not derived because of the overlapping of two energy loss peaks characteristic to magnesium oxide and surface layers.