The purpose of this paper is to discuss some elements of dynamical theory and to introduce some basic ideas on defect image formation in X-ray topographs. After some explanations of the basic principles of dynamical theory of X-rays, examples of defect contrast are given. Two examples of studies of quartz single crystals by X-ray topography are developed. First, the analysis of the X-ray spherical wave topographs of various Y-cut plates of synthetic quartz crystals show that the coherence of the lattice between the seed and the grown crystal is directly related to the density of the dislocations present in the seed. For the samples, the local deformations are essentially related to the density of the dislocations. Plane-wave topography shows that the local deformations can be estimated with good precision and related to the growth defects. The second example concerns Stroboscopic X-ray topography. With the use of synchrotron radiation, we have examined three quartz resonators. Several types of vibration modes and the perturbations due to the defects are described. Defects such as growth bands and especially dislocations disturb acoustic wave propagation in the crystals and can induce losses by untrapping a part of the energy of the mode conversion.
Scanning Microscopy: Vol. 1993
, Article 15.
Available at: https://digitalcommons.usu.edu/microscopy/vol1993/iss7/15