Planar defects and dislocations in HPHT as-grown diamond crystals

Abstract

In the present paper, diamond crystals approximately 0.8 mm in dimension were synthesized at high temperature and high pressure (HPHT) in the presence of FeNi catalyst in the diamond stable region. An argon beam-milling machine thinned the HPHT as-grown diamonds until they were suitable for examination by cross-sectional transmission electron microscopy (TEM). It was shown that there are a number of twins, stacking faults and dislocation networks on (111) planes in the HPHT-grown diamond crystals. During the diamond growth at HPHT, the growing diamond inevitably traps impurities. Dislocation networks near the zone relieve the concentration stresses caused by the impurity-enriched zones. Twins may be formed mainly due to the carbon atoms falling by mistake into positions where a twin crystal can form during diamond growth. Another possibility for twin formation in the HPHT as-grown diamonds is that twins are initially formed during the nucleation process as in CVD diamonds. Moiré images reveal that the density of stacking faults is high. The stacking faults may be formed mainly due to rapid growth of the diamond at HPHT. Another possibility for stacking faults formation is related to the condensation of supersaturated vacancies in the HPHT as-grown diamonds on the (111) plane during rapid quenching after diamond synthesis. The terminating of stacking faults on intersecting twins by moiré image 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.