MPCVD法中氮气对单晶金刚石生长机理影响的探究

Impact of Nitrogen Concentration on Monocrystalline Diamond Growth in Microwave Plasma Chemical Vapor Deposition

在微波等离子体化学气相沉积法同质外延生长单晶金刚石的过程中添加不同浓度的氮气,利用发射光谱、拉曼光谱等测试手段探究不同浓度氮气对等离子体以及单晶金刚石生长质量和速率的影响,通过分析等离子体内部基团强度的变化探究添加氮气对单晶金刚石生长机理的影响。探究发现:氮气的添加对于等离子体内基团的种类并没有明显改变,但随着氮气浓度的升高,CN基团的基团强度具有明显升高的趋势,C2基团的基团强度不断降低,单晶金刚石的生长速率不断提高。氮气并不是通过提高甲烷的离解度来产生更多的C2基团从而促进单晶金刚石的生长,而是作为一种催化剂加快单了晶金刚石表面的化学反应。当氮气浓度低于0.5%时,单晶金刚石的生长速率提高幅度较大且生长质量良好。但当氮气浓度超过0.8%时,单晶金刚石的生长速率逐渐趋近于饱和,且非金刚石相不断增多,生长质量不断降低,因而通入氮气的最佳浓度应该低于0.5%。

The influence of the nitrogen concentration on monocrystalline diamond growth in microwave plasma chemical vapor deposition was investigated with optical emission spectroscopy（ OES） and Raman spectroscopy for growth condition optimization. The results show that the added nitrogen concentration has a major impact. To be specific,as the N2-concentration increased,the intensity of CN radicals and the deposition rate increased,accompanied by a decrease of the C2 groups. At a N2-concentration below 0. 5%,high quality diamond grain grew rapidly,possibly because N2 catalyzed the surface reaction and surface crystallization instead of promoting decomposition rate of methane molecules; however,at a N2-concentration over 0. 8%,the diamond quality slowly deteriorated,though the deposition rate remained almost unchanged,simply due to increasing formation of non-diamond phase.