3D DuMond diagrams of multi-crystal Bragg-case synchrotron topography. II.Curved sample

The dimensional features of multi-crystal synchrotron X-ray topographs are explained by 3D DuMond diagrams for a flat double-crystal monochromator and a curved sample. Symmetric Bragg-case reflections are assumed for all crys tals. sigma-sigma and sigma-pi geometries are considered, where the diffrac tion plane of the sample is parallel and perpendicular, respectively, to th e vertical diffraction plane of the monochromator(sigma polarization). It i s shown that the shape of the sample image is closely connected to the shap e of the volume shared by the diffraction domains of monochromator and samp le in the 3D DuMond diagram. In particular, for the an set-up, the image sh ape depends on the curvature value and sign. An experiment is reported for this latter crystal geometry to determine lattice mismatch, its lateral hom ogeneity and curvature value and sign in a sample made of epilayer and subs trate.