Crystal Defects Analysis Of Synthetic Diamonds Under Several Different Conditions

Diamonds synthesized under different growth conditions were studied usingcontinuous spectra synchrotron radiation in this paper. Experiment techniques andcomputing principle of calculating the spatial orientation of the crystal defects wereintroduced. Calculation errors brought possible in the experiment was analyzed andamended in this paper. The crystal defects and spatial orientation of diamonds synthesizedunder different conditions are determined through analyzing and calculating theexperimental results. According to the type and distribution of defects and different crystalforms, the samples were divided into four kinds.Defects in these four kinds of crystals were mainly dislocations, stacking faults andgrowth bands. The defects distributing both sides of (001) were significantly different inthe first kind of crystals. So we divided them into two parts to discuss respectively. Thefirst part near the seed only have linear beam-like dislocations extending along the±[100]and±[010] directions. The crystal growth conditions were stable at this stage. A number offan-shaped beam of dislocations and stacking faults grew in the [001] direction in thesecond part. It was suggested that the crystal growth conditions at this stage had changed.It was found obviously that the defects in the second kind of crystals were less than that inthe first kind. There were a small amount of dislocations growing along the <211>direction and stacking fault parallel to {111} planes. The crystal growth conditions wererelatively stable. Different from the first two kinds of crystals, there were a large numberof growth bands in the third kind of crystals in which dislocations originating from theseed crystal surface had only a relatively small number. These dislocations straightdistributed along the <211> direction. The crystal growth conditions at this stage werestable. Lots of growth bands grew in the periphery of the crystals and parallel to {100},indicating the crystal synthesis conditions had changed and crystals grew unstable. Theinternal defects in the fourth kind of crystals had plenty of dislocations, growth bands anda few of stacking faults. The differences between the third and the fourth kind of crystalswere that the growth bands and stacking faults in the latter were parallel to the {110}, withdislocations mainly along <110>. The crystal growth conditions were also unstable. It was proposed that the crystal defects in synthetic diamond could be effectivelyreduced and the quality of the synthetic diamond could be improved obviously throughselecting the appropriate synthesis temperature and pressure, maintaining the stability ofsynthetic conditions, using fewer defects and stress-free crystal as a seed crystal.