Synthesis and Characterization of High Pure Diamaond Single Crystal

本课题为高纯金刚石单晶的合成奠定了基础。从基本观点出发，研究了目前唯一可行的单晶金刚石高压溶剂生长方法。研究了碳合金体系中金刚石形成的各种压力-温度区域，发现Ni-Ti和Fe-B等合金存在未自发成核的区域。这些区域的发现可以提供更好的P-T条件，仅在种子晶体表面选择性地进行晶体生长。研制了活塞缸式和立方顶锤式高压仪，建立了多种碳、溶剂合金体系压力下液相温度的差热分析方法。第三，我们研究了Ni-Ti溶剂作为一个典型的体系，因为Ti具有两种相反的功能，即防止氮污染到金刚石晶格的剂和作为包裹体向金刚石块体提供TiC和TiN的可能来源。结果表明，在最佳掺量的钛溶剂中可以生长出高纯度的金刚石晶体。金刚石晶格中的轻元素杂质可以通过SIMS和AES检测到，这些测量结果也可以与Ni杂质的分子轨道能量计算相关联。

This project was performed to establish basic scope of the synthwsis of high pure diamond single crystal. High pressure solvent growth method of single crystal diamond, which only possible method at present, was studied from basic view points. We examined various pressure-temperature region of diamond formation of the carbon alloy systems and found that some alloys such as Ni-Ti and Fe-B showed the region which no spontaneous nucleation of diamond was observed. The finding of these region canpropose better P-T condition to perform crystal growth only selectively on the surface of seed crystal.We developed piston cylinder type and cubic anvil type high pressure apparatus to establish DTA method to detect liquidus temperature under pressure for various carbon and solvent alloy system. Thirdly, we Thirdly, we examined Ni-Ti sovent as a typical system, because Ti has two opposed function namely agent to prevent nitrogen contamination to the diamond lattice and possible souce to supply TiC and TiN into diamond bulk as an inclusion. It was found that high purity diamond crystal can be grown in the solvent of an optimum amount of Ti.Impurities of light elements inthe diamond lattice could be detected by SIMS and possibly AES and these measurements can also corelate with molecular orbital energy calculation done for the case of Ni impurity.