抄録
Structural imperfections in synthetic diamond crystals prepared under high temperature-high pressure (HPHT) in the presence of Fe_<65>Ni_<35> catalyst have been examined by cross-sectional transmission electron microscopy (TEM). Etch pits on the (111) surface of the diamond, which are generated by the screw dislocations meeting the diamond (111) surface at the points of emergence of dislocations, can be revealed by chemical etching and used to study the motion of dislocations under the action of applied stress. There exist a number of hexagonal dislocation loops, twins, stacking faults and array of dislocations in the HPHT-grown diamond crystals. The hexagonal dislocation loops derive from supersaturated vacancies resulted from quenching from high temperature, the formation of vacancy disc on the (111) close-packed plane and its subsequent collapse form a dislocation loop. The twins may be formed due to the carbon atoms falling by mistake into positions where a twin crystal can form during diamond growth. Moire images reveal that the density of stacking faults is higher. The stacking faults may be generated by the condensation of supersaturated vacancies in the HPHT-grown diamonds on the (111) plane. The terminating of stacking faults on intersecting twins by moirg images suggests that the bordering partial has propagated by glide up to the twin interface during diamond growth, this may be described by the reaction of Shockley partial dislocation with a twin on the (111) plane. The array of dislocations may be related to the internal stress, which are caused by the micro-inclusions in the diamonds.
