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目的：研究不同甲烷体积分数对纳米金刚石( NCD)薄膜生长的影响,实现较小晶粒尺寸、高平整度的NCD薄膜的制备。方法采用微波等离子体增强化学气相沉积的方法制备NCD薄膜,以CH4/H2为气源,在生长阶段控制其他条件不变的前提下,探讨不同甲烷体积分数对NCD晶粒尺寸、表面形貌以及表面粗糙度的影响。采用SEM、XRD等观测NCD薄膜的表面形貌和晶粒尺寸大小,并利用Raman对NCD薄膜的不同散射峰进行分析。结果随着甲烷体积分数的增加,薄膜晶粒尺寸有减小的趋势。甲烷体积分数较低时,晶形比较完整,但致密度较小；甲烷体积分数较高时,晶形杂乱无章,但致密度较好。当甲烷体积分数为9%时NCD薄膜平均粒径达到最小,为21.3 nm,表面粗糙度较好,但非晶金刚石成分开始大量生成,NCD薄膜质量开始变差；当甲烷体积分数为8%时其形貌最好,且此时最小表面粗糙度小于20 nm。通过Raman分析可知NCD薄膜中出现了硅峰和石墨烯特征峰。结论甲烷体积分数对NCD薄膜形貌有较大影响,甲烷体积分数为8%时是表面平整度由较差变好再逐渐变差的分界点,且平均晶粒尺寸为23.6 nm,薄膜表面具有较好的平整度。

ABSTRACT:Objective To study the effect of different methane volume fractions on the growth of nanocrystalline diamond films, and to realize the preparation of NCD thin films with smaller grain size and high flatness. Methods Nanocrystalline diamond thin films were prepared by microwave plasma enhanced chemical vapor deposition method. The effects of different volume fractions of methane on the grain size, surface morphology and surface roughness of nanocrystalline diamond films were discussed with CH4/H2 as the gas source and other conditions kept constant during the growth period. The surface morphology and grain size of nanocrystal-line diamond films were observed by SEM and XRD, and the scattering peaks were analyzed by Raman. Results With the increase of methane volume fraction, the grain size of the films decreased. At low methane volume fraction, the crystal shape was complete, but less dense, while at high methane volume fraction, the crystal shape was disorganized, but the density was higher. When the methane volume fraction was 9%, the minimal average particle size of 21. 3 nm was reached, the surface roughness was good, but the quality of NCD films became poor, with massive generation of amorphous diamond components. At a methane volume fraction of 8%, the morphology was the best, and the minimum surface roughness was less than 20 nm. The Raman analysis showed that sili-con peak and graphene characteristic peaks occurred in the NCD films. Conclusion Methane volume fraction had a great effect on the quality of the nanocrystalline diamond films. The methane volume fraction of 8% was the dividing point of surface flatness changing from poor to good and then again changing gradually poor. Under this condition, the average grain size was 23. 6 nm, and the film surface was smooth.