High resolution X-ray techniques

Recent high resolution X-ray techniques for measurement of (i) diffuse X-ray scattering (DXS) (ii) low angle X-ray scattering (LAXS) and (iii) microstructural changes in semiconductors and insulators subject to high electric fields are described. In all these techniques, a highly collimated and monochromated Kα1 beam has been used as the exploring X-ray beam. This has been obtained by combining a fine focus or a microfocus X-ray source with special collimators and monochromators made out of dislocation free crystals. Detailed investigations of DXS on nearly perfect crystals of Si and alkali halide crystals have shown that at and near the room temperature, the elastic thermal waves or phonons do not give an appreciable contribution to the observed DXS, which is mainly due to point defects and their aggregates. Porosity in carbon fibres has been studied by using the LAXS measurements. A new technique for study of microstructural changes in insulators and semiconductors subject to high electric field is briefly described with illustrative results. (author)