In this study, the synergistic impact of boron, oxygen and titanium on growing large single-crystal diamonds was studied using different concentrations of B2O3 in a solvent-carbon system under 5.5-5.7 GPa and 1300-1500 ℃. The study found that it was difficult for boron atoms to enter the crystal when boron and oxygen impurities were doped using B2O3 without the addition of Ti. However, a high boron content was achieved in the doped diamonds that were synthesised with the addition of Ti. Additionally, boron-oxygen complexes were found on the surface of the crystal, and oxygen-related impurities appeared in the crystal interior when Ti added in the FeNi-C system. The results showed that the introduction of Ti in the synthesis cavity could effectively control the amount of boron and oxygen in the crystal. This not only has important scientific significance for understanding the synergistic influence of boron, oxygen and titanium on the growth of diamond in the earth, but also for the preparation of high-concentration boron or oxygen containing semiconductor diamond technologies.

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In this paper, large single crystals of diamond were synthesized in a pure Co-C system at 5.6 GPa and 1450–1470 °C. The diamond morphology, nitrogen content, and Co-related optical centres...