Dislocation distributions in brown diamond

Dislocation distributions are characterized on a µm‐scale in various plastically deformed natural brown type IIa diamond samples before and after high‐pressure high‐temperature (HPHT) treatment. Transmission electron microscopy (TEM) is 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 have been systematically determined for diamond samples before and after HPHT treatment. The total dislocation line density is about 10 9 cm –2 , and does not change upon HPHT treatment. A significant proportion of the dislocations have 〈112〉 line directions besides the 〈101〉 line directions. No changes in dislocation distributions before and after HPHT‐treatment are reported so far. However, the presence of many paired 〈112〉 dislocations and small dislocation loops suggest a link to the current brown colour mechanism involving vacancy clusters or disks. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)