Interpretation of transmission electron microscope images of amorphous silicon/germanium and silicon/iron multilayers

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Abstract
We show that the observed contrast in transmission electron microscope images of multilayer specimens composed of amorphous materials can be understood in terms of the scattering of electrons passing through the material. This leads us to develop a simple method of analyzing the image contrast to give quantitative information about the thicknesses of individual layers, which cannot be obtained by any other technique. The results of this analysis for images of silicon/germanium and silicon/iron multilayers are in good agreement with the results of small-angle x-ray scattering and the readings of quartz thickness monitors during the deposition of the layers. The accuracy of the thickness measurements we obtain from transmission electron microscope images is 7% for the average layer thickness of a single component and 10% for the thickness of individual layers when the layer thickness is about 4 nm, which is comparable to the accuracy which can be attained for crystalline layers.