Small-angle X-ray scattering of extended defects in diamonds

Results of the small-angle X-ray scattering (SAXS) of diamonds with different concentrations and types of optically-active defects are reviewed. It is shown that nitrogen-free (IIA) diamonds and diamonds with a low degree of nitrogen aggregation have no SAXS. Annealing of diamonds leads to the formation of three-dimensional clusters of defects with sizes in the range from ~8 to 60 nm. There is no correlation between nitrogen concentration and the existence or the size of the clusters, however, the clusters are related to the degree of diamond annealing. The presence of the clusters is unrelated to 'platelets' and they contain little, if any, nitrogen. With annealing, the size of the clusters decreases and the contrast of electronic density with the matrix increases.