Observation of X-ray topographs using Borrmann effect in the Bragg case

By tuning X-ray energy from synchrotron radiation, the plane wave topographs from a Ge crystal in the Bragg case are recorded at an energy for which the real part of the atomic scattering factor is zero and the imaginary part is approximately equal to zero. At the former energy the high reflectivity is obtained due to the Borrmann effect, and at the latter energy it is obtained due to the extinction effect. In diffraction topography, the defect contrasts at these two energies are almost the same. Differences exist in that some deeper defects can be seen at the former energy. This indicates that we can determine the depth of a defect by changing the resonance condition. In transmission topography the images of defects, the contrasts of which are the reverse of those in diffraction topography, are observed at the latter energy, but no such defect images are observed at the former energy.