Dislocation distributions were characterized at the µm-scale in various plastically deformed natural brown type-IIa diamond samples before and after high-pressure high-temperature treatment. Transmission electron microscopy was used for a statistical study. Applying conventional diffraction contrast imaging, different parameters such as the total dislocation line density, the distribution of <101> and <112> line densities, and Burgers vectors of dislocations were systematically determined for diamond samples before and after high-pressure high-temperature treatment. The total dislocation line density was about 109/cm2, and did not change upon high-pressure high-temperature treatment. A significant proportion of the dislocations had <112> line directions besides the <101> line directions. No changes in dislocation distributions before and after high-pressure high-temperature -treatment were reported. However, the presence of many paired <112> dislocations and small dislocation loops suggested a link to the current brown color mechanism involving vacancy clusters or disks.

Dislocation Distributions in Brown Diamond. B.Willems, P.M.Martineau, D.Fisher, J.Van Royen, G.Van Tendeloo: Physica Status Solidi A, 2006, 203[12], 3076-80