超薄四面体非晶碳膜的结构和性能

使用磁过滤阴极真空电弧(FCVA)技术制备不同厚度的超薄四面体非晶碳膜(ta-C),研究了表征和测量超薄ta-C碳膜微观结构和性能的方法以及膜厚的影响。使用X射线衍射仪验证椭圆偏振光谱仪联用分光光度计表征膜厚度的可靠性并测量了膜密度;用拉曼谱分析薄膜的内在结构,验证用椭偏联用分光光度计表征sp^3C含量的可靠性;用Stoney,s公式计算了薄膜的残余应力。结果表明,薄膜的厚度由7.6 nm增大到33.0 nm其沉积速率变化不大,为1.7±0.1 nm/min;根据椭偏联用分光光度计的表征结果,薄膜中sp^3C的含量逐渐减少,拓扑无序度降低,与拉曼谱的表征结果一致;厚度为7.6 nm的超薄ta-C碳膜中p^3C的含量最高;随着厚度的增大薄膜中的残余压应力从14 GPa降低到5 GPa;厚度为11.0 nm的薄膜主体层密度最大,为3070 kg/m^3,致密性较好;厚度对薄ta-C碳膜表面粗糙度的影响较小。用椭偏和分光光度计测量超薄ta-C碳膜的厚度和表征显微结构是可行的,X射线反射法可用于测量超薄ta-C碳膜密度和表面粗糙度,但是对薄膜的质量要求较高。

Structure and Properties of Ultrathin Tetrahedral Amorphous Carbon Films

Ultrathin tetrahedral amorphous carbon (ta-C) films with different film thickness were prepared by filtered cathodic vacuum arc technique. The accurate measurement of the film thickness and sp³C content of the ultrathin ta-C films was conducted by means of ellipsometry combined with spectrophotometry. The acquired film thickness was further verified by XRD. The film density was acquired from the results of precise determination of lattice parameters. Raman spectroscopy were conducted to characterize the atomic bond structure of as-prepared film. The residual stress was calculated from the curvature of the film/substrate composite using Stoney^，s equation. Results show that as the film thickness increased from 7.6 to 33.0 nm there was no obvious change of the ultrathin ta-C film growth rate, which keeps constant as 1.7±0.1 nm/min, while the residual compressive stress and sp³ fraction decreased; for the film of thickness 7.6 nm the maximal sp³ fraction was obtained. The results are consistent with Raman's. For the film of thickness 11.0 nm, the maximal bulk layer density was 3070 kg/m³. The film thickness had no obvious influence on surface roughness of ultrathin ta-C films. In summary, ellipsometry combined with spectrophotometry is of feasible means for characterizing the structure and thickness of the ultrathin ta-C films. X-ray reflection can be used to measure the density and surface roughness of ultrathin ta-C carbon films of high quality.