Double-crystal X-ray rocking-curve peak splitting due to interference in triple-layer epitaxic structures

The origin of peak splitting in double-crystal X-ray rocking curves of epitaxic layer structures comprising two layers sandwiching another of different composition is examined both with Takagi-Taupin dynamical theory simulation and the semi-kinematical model of Tapfer & Ploog. It is shown that the splitting occurs for specific phase differences between waves diffracted from the top and bottom layers. Thicknesses at which a minimum intensity occurs in the peak centre are calculated using the semi-kinematical formalism and compared with the results of the full dynamical-theory simulations. It is argued in the present paper that the semi-kinematical theory can give a clear quantitative description but not an accurate quantitative result in analyzing complex epitaxic structures.