Topographic EXAFS

Abstract

The EXAFS (or extended X-ray absorption fine structure) method of absorption-edge spectroscopy for the determination of crystal bond lengths and coordination number, especially in the first coordination shell, is in very widespread use in chemical, crystallographic, biological and to some extent metallurgical research. The high-resolution method of X-ray diffraction topography, which reveals crystal defects, is likewise widely used in studies on crystal growth, phase transformations, chemical decomposition and mechanical properties and domain studies: that is, in the area of ‘microstructure’ rather than ‘crystal structure’. It is obvious that the techniques are complementary and that both could be required to solve a particular problem—structural changes induced by segregation at a surface or internal interface, for example. However, up to now, EXAFS data have been taken only as an average over large samples, thus losing all microstructural information, and topographic data have not provided structural, bonding or chemical information. We present here the first experimental method of combining these experiments, simultaneously on one specimen.