X-ray Topo-Tomography of Large HPHT Synthetic Diamonds

Extended defects in large synthetic diamonds grown at high pressures and high temperatures (HPHT) using the thermal gradient method were studied by X-ray topo-tomography with a laboratory setup. It is shown that the temperature and growth rate are the principal factors influencing the crystalline quality of the diamonds. Synthesis at high temperatures and low rates allows growth of single crystals with a low density of dislocations, stacking faults, and microtwin lamellae. The annihilation kinetics of the extended defects during annealing at high pressure implies important role of vacancy diffusion. The annihilation of such defects leads to formation of perfect dislocations.