X-ray diffraction techniques for the analysis of epitaxic thin films

The use of X-ray diffraction for identification and analysis of thin epitaxic layers, grown on a single-crystal substrate of alien material, is often complicated by the predominant diffraction of the substrate, which may obscure that of the layer, and the incidence of `substrate-imposed' twinning. Techniques have been devised whereby control of the incident radiation spectrum and the angles of diffraction enables the X-ray diffraction pattern of the layer to be enhanced. Information concerning the identity of the material and its orientation with respect to the substrate surface is readily obtained, followed by analysis of the epitaxic relationships and twinning modes. The use of X-ray intensity data is discussed, with particular reference to the determination of crystallographic polarity, and a method for the precise measurement of the lattice parameter of thin films is presented, which is applicable to the characterization of solid solutions.