X-ray topographic and optical imaging studies of synthetic diamonds

Large synthetic diamonds grown by the reconstitution method, all exhibiting the growth forms {100}, {111}, {110} and {113}, were studied. Crystal perfection was assessed by X-ray topography using a conventional source of Cu Kα₁ radiation and employing the section, projection and limited-projection topographic techniques. For the mapping of growth-sector configurations, cathodoluminescence topography, birefringence micrography and colouration mapping were also employed. Observations on three diamonds are detailed. Each specimen possessed a parallel pair of mechanically polished surfaces, which had orientations ±(100), ±(111) and ±(110), respectively. The overall widths and thicknesses of the three specimens were as follows: the ±(100) faceted, 3.2 and 0.76 mm; the ±(111) faceted, 2.5 and 0.92 mm; the ±(110) faceted, 5 and 0.7 mm. Dislocation densities and trajectories, and the widths and contrast of individual dislocation images, are described. The variation of visibility of dislocation images in birefringence micrographs and in X-ray topographs as a function of line orientation was investigated. Other topics discussed include structure and contrast in X-ray topographic images of growth-sector boundaries and fine structure in images of small inclusions and surface indentations.