On epitaxial misorientations

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Abstract
A study is presented of epitaxial misorientations in thin films of silicon and cadmium telluride on sapphire. The symmetry theory of line defects in interfaces is used to show that there is a large number of different interfacial dislocations which are possible in both systems. Coordinate transformation matrices are derived, using Frank's four-vector method for hexagonal crystallography, and applied in order to identify the Burgers vectors of plausible dislocations. A geometrical model is developed which predicts that the dislocations formed at substrate surface features due to vicinal offcut and substrate surface roughness can lead to misorientation of the epitaxial deposit away from the nominal orientation relationship. X-ray goniometry is used to measure the substrate vicinal angle and misorientation angle from wafers of silicon and cadmium telluride on sapphire. A strong correlation between vicinal angle and misorientation measurements was found, and these data gave a good fit to the geometrical model.