Abstract
X-ray topography is a useful and non-destructive way to reveal the quality of single crystals, and X-ray topography experiment is built on X-ray diffraction. Lattice defectsand X-ray diffraction phenomenon can be observed from the contrast and distribution of diffraction intensity of 2D topographic images. We have set up an X-ray topographicarrangement at the NSRRC BL07A by following a multiple crystals technique. The monochromatic X-ray beam from Si double-crystal monochromator (DCM) is enlargedand collimated by a third Si crystal at 19keV via the (115) asymmetric reflection, then the specimens are illuminated in a Laue diffraction geometry and the diffraction images arerecorded. Also, we have observed high absorption contrast X-ray diffraction topographs by using low energy (8.4keV) X-rays via the Si (115) asymmetric reflection.A charge couple device (CCD) is used as the detector for image recording. The results show no image contrasts of Si crystals, indicating that Si crystals are perfect. It isfound that there are many dislocation lines on sapphire (Al2O3) topographic images, and the dislocation density is different for different crystal growth method or grade. We can also relate dislocation density with the FWHM of rocking curve. In the end, the dynamical diffraction contrasts and Pendell sung effect have been observed in the highabsorption contrast diffraction imaging. Detailed experimental results will be presented.