On the question of microcrystallites in some amorphous materials. An electron microscope investigation

Abstract

High resolution dark‐field electron microscopy on amorphous thin films of Ge, GeTe, PdSi, and AuNi show coherently scattering regions to be 5 to 7 Å rather than the 15 Å found in lower resolution instruments. Fringe‐like contrast found in tilted beam interference micrographs and used in support of the microcrystallite model by Howie et al. is shown to be caused by instrumental aberrations introduced by the tilted beam method. It is found that the number of fringes increases with tilt angle contrary to the model proposed by Berry and Doyle which predicted a single fringe if the second amorphous halo is used for interference. Using thin (≈20 Å) films of Ge and untilted interference microscopy the contrast is found to comprise typically of one to two fringes. The extent of the fringe was of the order of 6 Å. An occasional alignment leading to fringe contrast over larger areas was also observed. These observations are consistent with random network or dense random packed models for amorphous solids. Copyright © 1974 WILEY‐VCH Verlag GmbH & Co. KGaA