Crystal Defects Analysis Of Diamonds Synthesized Under Several Different Conditions

Three groups of diamonds synthesized under different conditions are studied using continuous spectra synchrotron radiation, FTIR, Raman and SEM in this paper. The samples of the three groups were all synthesized in the conditions of slow heating and holding in constant temperature, but the desending speed were different. The desending speeds were slow, quick and very quick of the samples of the first(SCS), second(SCQ) and third(SCQQ) group. The type of impurities, crystalline defects, the relationships between the characteristics of the spatial orientation and the impurities of three groups of synthesized crystals are analysed. Combining with the synthesizing conditions of the crystals, the relationship between different cooling speeds and crystalline defects are also studied in this paper.The FTIR spectrums show that besides nitrogen and hydrogen there are also boron and phosphorus in the first group specimens. From the diffraction images of the continuous spectra synchrotron radiation, the two primary forms of the defects in three different groups of synthesized diamonds are dislocations, stacking faults and other planar defects., The specimen D16-6 of the first group including phosphorus mainly has a defects layer under the crystal surface 0.56~0.63 mm which the density of the dislocations is relatively higher in the layer. And the spatial orientations of the dislocations are between <111> and <112>.Combining with the FTIR, we find that the spatial distribution of the dislocations and phosphorus are the same. D16-6 diamond including boron mainly has a defects layer under the skin 0.58~0.69 mm which the density of the dislocations is also relatively higher in the layer, but the diffraction contrast of the defects layer is weaker than D16-6. The diamonds doped both with boron and phosphorus have defects layer under the surface of the crystal 0.60~0.76 mm, and the diffraction contrast of the defects layer is similar to the diamonds with phosphorus.In the second and the third groups of the samples, besides the grown-in dislocations and faults, there are also planar defects which cut the grown-in dislocations. Only few planar defects are found distributed sporadicly in the specimens of the second group, which are mainly parallel to {100}. Several planar defects parallel to each other gethered in groups are observed in the samples of the third group which distributed from {110} to {113}. The density of the planar defects in the samples of the third group is higher than in the second group. The distances between the planar defects are 0.068 and 0.086 mm. Because these plane defects cut the dislocations, stacking faults and other grown-in defects, it shows that they are formed after the grown-in defects, and also proves that they are caused by the quick cooling process. As there are more these planar defects in SCQQ samples than in SCQ samples, it indicates that the quick cooling process and quick stop process have a bad effection to the qulity of the synthesized diamonds.