X-RAY-DIFFRACTOMETRY OF SMALL DEFECTS IN LAYERED SYSTEMS

X-ray diffraction in thin layers and layered systems is described using the optical coherence approach and the semi-kinematical diffraction theory. Two defect models in thin layers are considered-the mosaic structure model and the model of interface roughness. For both defect models the reflection curves of a thin layer and a superlattice have been calculated and compared with double-crystal x-ray diffractometry results on superlattices and epitaxial layers. The distribution of the diffusely scattered intensity near a reciprocal lattice point has been calculated theoretically for both models and it has been proved experimentally by double- and triple-crystal diffractometry of epitaxial layers with mosaic structure. It has been demonstrated that the theory yields a tool for estimating the predominant defect type in a layered structure.