STUDY OF STRUCTURAL EVALUATION FOR CRYSTAL BY USED BORRMANN EFFECT

点击翻译按钮获取中文摘要

The purpose of this research is the analysis about the changes of the contrasts for lattice defects in X-ray plane wave topographs, which were recorded for GaAs 200 reflection at different conditions of atomic resonant scattering near the K-absorption edges of Ga and As.In the Laue case, the plane wave topographs of X-rays for GaAs 200 reflection were taken using synchrotron radiation in KEK-PF near the K-absorption edges of Ga and As. The topographic contracts caused by lattice defects were changes by tuning X-ray energy to four typical resonant scattering conditions. The sharp image of lattice defect was observed when the Borrmann effect disappeared. When the Borrmann effect was conspicuous, the image of lattice distortion around a dislocation was observed, and its contrast was reversed by changing the phase factor of resonant scattering.In the Bragg case, the plane-wave topographs with Ge844 reflection were taken near the Ge K-absorption edge by using the synchrotron radiation. The black-white contrasts of lattice defects were reversed besides the general changes in topographic images with the changes of X-ray energy. These phenomena have been analyzed by the resonant dynamical theory of diffraction. The explanation is brought out that two elements are responsible for the inverse of contrast, one is that the absorption increases due to the anomalous absorption of the extinction effect and the strengthening of the mean absorption, and another is that the absorption decrease due to the anomalous transmission of the Borrmann effect and the weakening of the mean absorption and the extinction effect. Meanwhile, it is revealed that the images in which the extinction effect is dominant are different greatly from the ones in which the Borrmann effect is dominant. Such properties about synchrotron radiation topography can be expected to turn out to be an attractive tool to examine structural imperfections.