Investigation on defects in HPHT-grown diamond single crystals

In the diamond single crystals synthesized at high temperature and high pre ssure using FeNi as catalyst, there are usually supersaturated vacancies an d inclusions formed during the diamond crystal growth and rapid cooling fro m high temperature. Some defects such as prismatic dislocation loops, stack ing faults and array of dislocations are closely related to such supersatur ated vacancies and inclusions. The supersaturated vacancies agglomerate int o discs on the (111) close-packed planes, subsequent collapse of the discs forms the dislocation loops and stacking faults. The thermal internal stres ses, which are caused by the difference of thermal contraction between the diamond and the inclusions due to the difference of thermal coefficients be tween them as the diamond is cooled from high temperature, may be relieved by the formation of array of dislocations. In the present paper, these defe cts in the diamond single crystals were directly examined by transmission e lectron microscopy (TEM). The characteristics and formation process of thes e defects were analyzed briefly. (C) 2001 Kluwer Academic Publishers.