Interpretation of electron micrographs and diffraction patterns of amorphous materials

Abstract

The image contrast from amorphous materials studied by dark field or by interference electron microscopy using tilted illumination is quantitatively discussed in terms of the microcrystallite model and of the random network model using a network model for SiO2. The experimental observations of bright spots of diameter > 10 Å. in dark field and of lattice fringes in interference micrographs are well explained by the microcrystallite model but cannot be accounted for by the random network model. The random network gives rise to a number of interesting diffraction effects, however, in particular to very small rather intense bright spots of diameter <3 Å. in dark field images. On the basis of the microcrystallite model some further improvements are described for the analysis of the diffraction pattern interference function to allow for intercrystalline effects and grain boundary material.