掺氮类金刚石薄膜的纳米力学及纳米摩擦特性研究

Nano-Mechanical Properties and Nano-frictional Behaviors of Diamond-Like Carbon(DLC) Films Doped with Different Nitrogen Contents

利用微波电子回旋共振化学气相沉积技术制备了不同氮掺杂量的类金刚石(DLC)薄膜,采用俄歇电子能谱仪、R am an光谱仪和Hys itron型纳米力学测试系统对掺氮类金刚石薄膜的化学成分和结构、纳米力学及其纳米摩擦特性进行研究.结果表明:反应气体中氮气流量比例越大,类金刚石薄膜中的氮含量越高;随着薄膜中氮含量增加,掺氮类金刚石薄膜中sp3比例下降,sp2比例明显增加,而薄膜的纳米力学性能如纳米硬度和弹性模量明显下降;纳米划擦试验中的划痕深度与薄膜中氮含量有关,当载荷相同时,氮含量越高,所对应的划痕深度越深;名义摩擦系数(LF/NF)随着载荷增加而增大;当载荷相同时,摩擦系数与沉积膜中的氮含量无关.

Diamond-like carbon （DLC） films doped with different nitrogen contents were prepared by a Microwave Electron Cyclotron Resonance deposition technique. Compositions and structures of the resultant N-doped DLC films were characterized using Auger Electron Spectrometer （AES） and Laser Raman Spectroscopic technique. Nano-mechanical properties were determined using a Hysitron Triboindenter system equiped with a Berkovich diamond tip at an applied load of 10 000μN. The nano-frictional behavior was examined with Triboindentor equiped with a conical diamond tip at normal loads of 1 000μN, 5 000μN and 10 000μN, respectively, where nominal coefficient of friction （μ） was defined as the ratio of lateral force （LF） and normal load （NF）. Depths for the scratched tracks were obtained using an Atomic Force Microscope （AFM） attached to the Triboindentor. Results shows that higher nitrogen contents in N-doped DLC films can be obtained by increasing N2 flow rate in reactive gas mixture. With increasing of nitrogen content in the films, resultant N-doped DLC films show a monotonously drop of sp3 and a significantly increase of sp2, and accordingly, their nano-mechanical properties, including nano-hardness and reduced modulus, decrease clearly. In addition, depths for the scratched tracks produced during scratch testing strong depend heavily on nitrogen content in the N-doped DLC films, and, at the same applied loads, the higher the doped nitrogen content, the deeper the resulting scratched tracks. For DLC films doped with different nitrogen contents, however, nominal coefficient of friction （LF/NF） deduced from nano-scratch testing at same loads is similar, and, therefore, seems to be independent of the added nitrogen content.