TOPOGRAPHIC METHODS FOR STUDYING DEFECTS IN DIAMONDS

Ways for mapping properties of surfaces or interior volumes of crystals are explained and applications to synthetic diamonds are presented. The methods, all of image-forming type, include topography of surface relief (including that due to differential abrasion resistance) and of internal variations of optical absorption and refractive index. High sensitivity to internal strains is provided by birefringence topography and by diffraction topography using X-rays from conventional and synchrotron sources. These detect dislocations, stacking faults, stress-producing inclusions and variations in lattice parameter. Complementary information comes from cathodoluminescence topography. Optical imaging methods for producing cathodoluminescence topographs are outlined and discoveries of polarized cathodoluminescence made with these techniques are described. The informativeness of combinations of several topographic techniques applied to a given specimen is demonstrated.