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 发布时间:2011/10/13 阅读:49525

2.5. Influences of impurities   2.5杂质的影响
Impurities are known to disturb crystal growth, and in low-pressure synthesis of diamond they also influence the diamond crystal morphology in many other cases. Impurities are usually introduced by additions to the source gas or by substrate evporation. The addition of foreign gases like N2, PH3 or boron compounds, etc. can change the diamond morphology from faceted to ballas with increasing concentrations. In all cases Raman spectra showed clearly the formation of the ballas diamond.   我们知道,杂质对晶体长大有影响,而且在许多其它情况下,对金刚石低压合成中的金刚石晶体形貌也有影响。杂质通常是由气体源或基体蒸发带入。加入诸如 N2、PH3或硼化合物等外部气体能使金刚石的形貌随着各含量的增加从多面金刚石变成半刚石。就一切情况而论,拉曼光谱明显反映了半刚石的形成。
The occurrence of impurities during the deposition process can also be caused by the evaporation of certain substrate materials. This was observed by diamond deposition on iron substrates where, due to the high vapor pressure of iron, ballas is formed at methane concentrations lower than 0.4%.   沉积过程中杂质也可因某些基体材料的蒸发而产生。这一点是在铁基体上沉积金刚石时发现的。这时,由于铁的蒸汽压力很高,在甲烷浓度低于0.4%时可形成半刚石。
2.6. Gas pressure and velocity   2.6气体压力和速率
Gas pressure strongly influences the gas activation whereby-at a constant activation temperature-with increasing gas pressure, a definitely lower dissociation rate of hydrogen occurs due to changes in the thermo-dynamic equilibrium. Additionally increasing the gas pressure reduces the amount of atomic hydrogen due to higher recombination in the gas phase.   气体压力会大大影响气体的活化作用,因此,在一固定活化温度下,随着气压的升高,热动力平衡发生变化,从而出现一个肯定更低的氢气离解速率。另外,由于气相中高度复合的缘故,提高气压可减少原子态氢的数量。

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