低浓度氩气对金刚石薄膜的影响及机理研究

Growth-Rate Enhancement of Diamond Coatings with Low Concentration Argon and Possible Mechanisms

提高生长速率是降低金刚石薄膜应用成本的关键因素之一,目前研究的提高速率的方法中以偏压电子增强为主,而该方法不适宜表面复杂的刀具涂层。本文通过在无偏压热丝化学气相沉积沉积金刚石薄膜条件下添加少量的Ar,成功将生长速率提高3倍,并采用等离子发射光谱研究了其反应机制,尤其对反应系统电子温度的变化做出了详细推理分析。实验结果采用扫描电镜、Raman光谱进行表征。结果表明:氩气的添加不仅可促进二次成核,使得晶粒尺寸达到纳米级,而且一定量的氩气(8%~32%)可提高金刚石薄膜的生长速率,当氩气含量在8%~32%范围内时,金刚石薄膜的生长速率随氩气浓度增大而增大,本实验获得最高生长速率达3.75μm/h,是无Ar情况下的3倍。光谱诊断显示的主要基团为CO(283~370nm),CH(387.0 nm),H_β(486 nm),H_α(656.3 nm),氩气添加后这些基团的光谱强度均显著增强。当氩气含量为7%~30%时,电子温度与氩气浓度成正比,为金刚石薄膜的生长提供了更优越的条件,生长速率得到提高。

The deposition rate of the diamond coatings,synthesized by bias-free hot-filament chemical vapor deposition（ HFCVD） in a mixture of H2,C3H6O and Ar,was increased by 3 times. The influenceof the Ar concentration on the microstructures and growth mechanisms of diamond coating was investigated with scanning electron microscopy,Raman spectroscopy and optical emission spectroscopy（ OES）. The results show that addition of argon significantly increased the growth rate of the high quality diamond coatings. To be specific,as the Ar concentration increased from 0%-32%,the growth rate increased up to 3. 75μm/h,possibly because the increasing secondary nucleation promoted the formation of diamond nano-grains and because of Penning discharge. In addition,Ar addition strongly enhanced the electron temperature and emission intensities of the major free radicals observed,including CO,CH,Hβ and Hα.