Crystals which were about 0.8mm in size were synthesized at high temperatures and high pressures in the presence of FeNi catalyst in the diamond stable region. An Ar beam-milling machine thinned the high-temperature high-pressure as-grown diamonds until they were suitable for examination by cross-sectional transmission electron microscopy. It was shown that there were a number of twins, stacking faults and dislocation networks on (111) planes in the high-temperature high-pressure grown crystals. During growth at high temperatures and high pressures, the growing diamond trapped impurities. Dislocation networks near to the zone relieved the concentration stresses caused by the impurity-enriched zones. Twins could form, due mainly to C atoms falling by mistake into positions where a twin crystal could form during diamond growth. Another possibility for twin formation in high temperature and high pressure as-grown diamonds

was that twins initially formed during nucleation; as in the case of chemical vapour deposited diamonds. Moiré images revealed that the density of stacking faults was high. The stacking faults could form due mainly to rapid growth of the diamond at high temperatures and high pressures. Another possibility for stacking-fault formation was related to the condensation of supersaturated vacancies, in high-temperature high-pressure as-grown diamonds, on the (111) plane during rapid quenching after diamond synthesis. The termination of stacking faults on intersecting twins, as seen in Moiré images, suggested that the bordering partial propagated by glide up to the twin interface during growth. This could be described by the reaction of Shockley partial dislocations with a twin on the (111) plane.

Planar Defects and Dislocations in HPHT As-Grown Diamond Crystals. L.W.Yin, M.S.Li, J.J.Cui, Y.J.Bai, B.Xu, J.H.Gong, Z.Y.Hao: Diamond and Related Materials, 2002, 11[2], 268-72