低氮掺杂对含氢类金刚石结构和力学性能的影响

Effect of low nitrogen doping on the microstructure and mechanical properties of hydrogenated diamond-like carbon films

为探讨低氮掺杂对含氢类金刚石组织结构和力学性能的影响.采用非平衡磁控溅射和等离子增强化学气相沉积(PECVD)复合技术,在316不锈钢和硅片上制备碳化钨过渡层和不同掺氮量的含氢类金刚石薄膜(a-C:H(N)).通过拉曼光谱、X射线衍射(XRD)、X射线光电子能谱(XPS)和扫描电镜(SEM)对薄膜组织结构进行表征,薄膜的硬度和残余应力采用微纳米力学综合测量系统和薄膜应力测量仪进行表征.结果表明随着氮掺杂,薄膜形成碳氮键(CN)且其主要以C=N键形式存在,C=N/CN的比值随着薄膜氮含量增加逐渐下降.同时当掺氮量从0增至0.12 at%时,薄膜I_D/I_G比值迅速下降,sp^2C=C/sp^3C-C比值由0.65降至0.563,而薄膜硬度基本不变,约为20.4 GPa,残余应力则由3.35 Gpa降至1.31 GPa;随着掺氮量进一步增加,sp^2C=C/sp^3C-C比值增加,薄膜硬度迅速下降,残余应力则缓慢降低.可知氮的掺杂对DLC薄膜结构的影响有临界值0.12 at%,当掺氮量低于该值时,氮掺杂促进sp^3杂化的形成,薄膜具有较高的sp^3杂化含量.而随着薄膜含氮量进一步增加,sp^3杂化含量下降.同时当低氮掺杂时,可获得具有较高硬度以及较低残余应力的薄膜.

This paper aims to study the effect of low nitrogen doping on the microstructure and mechanical properties of hydrogenated diamond-like carbon films. By using unbalanced magnetron sputtering and plasma enhanced chemical vapor deposition(PECVD) composite technology, tungsten carbide transition layer and hydrogenated diamond-like carbon films with different nitrogen content(a-C:H(N)) were prepared on 316 stainless steel and silicon substrates. The microstructures of the films were characterized by Raman spectroscopy, X-ray diffraction analysis(XRD), X-ray photoelectron spectroscopy(XPS), and scanning electron microscope(SEM). The hardness and residual stress of the films were characterized by micro and nano mechanical comprehensive measurement system and film stress measuring instrument. Results show that with nitrogen doping, carbon-nitrogen bond(CN) was formed in the films and mainly existed in the form of C=N bond, and the ratio of C=N/CN decreased with the increase of nitrogen content. When the nitrogen content increased from 0 to 0.12 at%, the I_D/I_G ratio of the film decreased rapidly, the ratio of sp^2C=C/sp^3C-C decreased from 0.65 to 0.563, whereas the hardness of the films remained unchanged at about 20.4 GPa, and the residual stress decreased from 3.35 GPa to 1.31 GPa. With the increase of nitrogen content, the ratio of sp^2C=C/sp^3C-C increased, the hardness of the films decreased rapidly, and the residual stress decreased slowly. The effect of nitrogen doping on the microstructure of DLC films has a critical value of 0.12 at%. When the amount of nitrogen doping is lower than this value, it promotes the formation of sp^3 hybridization, and the film has high sp^3 hybridization, while the sp^3 hybridization of the films decreases with the increase of nitrogen, and the sp^3 hybridization decreases. The films with higher hardness and lower residual stress can be obtained with low nitrogen doping.