Synthesis and Characterization of High Pure Diamaond Single Crystal

本项目旨在确定高纯金刚石单晶合成的基本范围。从基本观点出发，对目前唯一可行的单晶金刚石高压溶剂生长方法进行了研究。我们考察了碳合金系统中不同的金刚石形成压力-温度区域，发现一些合金，如Ni-Ti和Fe-B等，没有观察到金刚石自发形核的区域。这些区域的发现可以提供更好的P-T条件，只在晶种表面选择性地进行晶体生长。我们研制了活塞式圆柱式和立方砧式高压装置，建立了差热分析(DTA)方法，对各种碳和溶剂合金体系的加压下的液相线温度进行了检测。第三，我们考察了作为典型体系的Ni-Ti体系，因为钛具有两种对立的功能，即防止氮气污染金刚石晶格的试剂和作为包裹体的TiC和TiN的可能来源。研究发现，在适量的钛的溶剂中可以生长出高纯度的金刚石晶体。用SIMS和可能的俄歇电子能谱可以检测到金刚石晶格中的轻元素杂质，这些测量结果还可以与对镍杂质情况下的分子轨道能进行关联。

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.