Analysis of high resolution electron microscope images of the Pd2Si-Si interface

High resolution electron micrographs have been obtained from Pd2Si-Si(111) interfaces viewed edge on and a detailed analysis of the interface structure has been carried out using computer simulations of the images. Since the stacking sequence of hexagonal Pd2Si is AαAαAα…, the question whether the interface plane of Pd2Si is silicon rich, A, or silicon deficient, α, has been investigated. An advancing interface cannot be planar at all stages of growth; therefore the question of interface roughness along the direction of the electron beam and twinning orientations has been considered. This has been modeled by Fourier shift techniques incorporated into multislice dynamical theory and, of course, is complicated by the dynamical diffraction conditions of the structure and the contributions of high order Bragg reflections to image detail. It has been possible to access the image features present in Pd2Si/Si micrographs and to point out the difficulties which are encountered not only in this system but in a wide variety of interface structures by high resolution electron microscopy. Perhaps the most important finding of this study is that the interface region contains a mixture of silicon-rich and silicon-deficient Pd2Si planes adjacent to the silicon side of the interface.