Synthesis and growth mechanism of diamond and cubic boron nitride

本文对金刚石和立方氮化硼的形成和生长机理进行了综述。在本研究中，我们使用了Ni、Ni-Ti、Ni-Nb、Fe-B、Fe-Co和Fe-Co-Ti等金属合金溶剂进行了金刚石的合成和生长实验。采用CaLiBN_2等碱金属及碱土氮化硼化合物作为生长CBN的溶剂，通过添加吸气剂元素Ti、Zr、Nb可去除金刚石中的主要杂质氮化物。然而，关于氮气吸杂机理的研究报道很少。加入较高的钛含量或在较高温度下生长，可显著降低金刚石晶体中的氮含量。采用Fe-Co-Ti合金作为溶剂，氮含量显著降低。利用金刚石在晶种上的再结晶过程，我们开发了高纯金刚石的生长方法。CaLiBN_2作为CBN生长的溶剂，晶体结构分析表明，结构中存在Li和N缺陷，这些缺陷可能起到降低CBN形成的阈值压力的作用。

On the formation and growth mechanism of diamond and cubic BN carried out in the present study will be summarized.In the present study, we used metal alloy solvents such as Ni, Ni-Ti, Ni-Nb, Fe-B,Fe-Co and Fe-Co-Ti used for diamond synthesis and growth experiments. Alkali and alkaline earth boron nitride compound such as CaLiBN2 was used as solvent for cBN growth.Nitrogen, which is a major impurity in diamond, can be eliminated by the addition of getter element such as Ti, Zr and Nb. However, few studies have been reported on the mechanism of the nitrogen gettering. Content of nitrogen in the diamond crystals decreased greatly by adding higher Ti content or growth at higher temperature. The content of nitrogen decreased remarkably when we use Fe-Co Ti alloy as solvent.We developed growth method of high pure diamond utilized recrystallization process of diamond on the seed crystal.Crystal structure analysis of CaLiBN_2 which used as solvent of cBN growth suggested that Li and N defect are present in the structure and these defects plays possible role of decreasing threshold pressure of the cBN formation.