X-RAY-DIFFRACTOMETRY OF SMALL DEFECTS IN LAYERED SYSTEMS

X-ray diffraction in thin layers and layered systems is described usin g the optical coherence approach and the semi-kinematical diffraction theory. Two defect models in thin layers are considered-the mosaic str ucture model and the model of interface roughness. For both defect mod els the reflection curves of a thin layer and a superlattice have been calculated and compared with double-crystal x-ray diffractometry resu lts on superlattices and epitaxial layers. The distribution of the dif fusely scattered intensity near a reciprocal lattice point has been ca lculated theoretically for both models and it has been proved experime ntally by double- and triple-crystal diffractometry of epitaxial layer s with mosaic structure. It has been demonstrated that the theory yiel ds a tool for estimating the predominant defect type in a layered stru cture.