Synthesis and Nanotribology of Superhard Carbon Nitride Films

采用自行研制的屏蔽电弧离子镀工艺成功地制备了非晶氮化碳（a-C：N）薄膜。在这项研究中，进行了基础研究，以应用的a-C：N薄膜作为新型超硬涂层。通过红外光谱和X射线光电子能谱表征了沉积膜的化学组成和成键状态。使用摩擦学仪明确了纳米力学性能。<Chemical Bonding States>我们改变氮气压力和衬底偏压作为沉积参数。随着氮气压力的增加，氮组成增加到N/C组成比为0.45。而C-C键和C-N键分别变为类石墨和类piligine状态，具有二维平面网络结构。施加负的衬底偏压会引起生长中的薄膜表面的离子轰击，从而导致薄膜中sp^3键态的形成。一 关于我们 然而，当负偏压超过n时，sp^3键的石墨化程度增加，同时氮的组成减少。在高氮气压条件下，由于电弧等离子体中离子的平均自由程较短，负偏压的影响减小。因此，sp杂化比和N/C组成比能够通过氮气压力和负衬底偏压来控制。<Nanomechanical Properties>利用摩擦学显微镜测量了在不同氮气压力和负衬底偏压下制备的a-C：N薄膜的纳米硬度。对于所有样品，膜厚度统一为150 nm。纳米硬度随着氮气压力和负衬底偏压的增加而降低。这一结果与高氮压使薄膜中的C-N键为类piligine键而不是3D C-N网络以及衬底负偏压过量使薄膜中的碳网络为类sp^2键的事实相一致。最硬的a-C：N薄膜显示出比广泛用作硬涂层材料的TiN膜更大的纳米硬度。用摩擦磨损试验机研究了复合材料的纳米磨损性能。用Vercobich型金刚石针尖在低载荷下扫描薄膜表面1μm × 1μm区域后，用原子力显微镜观察该区域的磨损深度。其纳米耐磨性能远优于已应用于耐磨涂层的类金刚石薄膜。这些结果表明，本研究中合成的a-C：N薄膜在摩擦学相关领域具有重要的应用价值。少

We have succeeded to synthesize amorphous carbon nitride (a-C : N) thin films by using the shielded arc ion plating process developed by ourselves. In this study, fundamental investigations were performed in order to apply the a-C : N thin films as novel super hard coatings. Chemical compositions and bonding states of the deposited films were characterized both by infrared spectroscopy and by X-ray photoelectron spectroscopy. The nanomechanical properties were made clear by using Triboscope.<Chemical Bonding States>We varied a nitrogen gas pressure and a substrate bias as deposition parameters. As increasing the nitrogen pressure, the nitrogen composition increased up to the N/C composition ratio of 0.45. However the C-C and C-N bonds became graphite-like and piligine-like states, respectively, which had 2D plane network structures. Applying negative substrate biases invoked ion bombardments on the growing film surfaces, which caused formation of the sp^3 bonding states in the films. A … More n excess of the negative bias, however, raised both a graphitation of the sp^3 bonding states and a decrease in the nitrogen composition at the same time. In the condition of the high nitrogen pressure, the effect of the negative bias was reduced due to the short mean free path of the ions in the arc plasma. Thus the sp hybridizing ratio and the N/C composition ratio was able to control by the nitrogen gas pressure and the negative substrate bias.<Nanomechanical Properties>By using Triboscope, we measured nanohardness of the a-C : N films prepared at various nitrogen gas pressures and negative substrate biases. The film thickness was unified at 150 nm for all samples. The nanohardness was degraded with increase both in the nitrogen pressure and in the negative substrate bias. This result was consistent with the fact that the high nitrogen pressure makes the C-N bonds in the films be the piligine-like states instead of the 3D C-N networks, and that the excess of the negative substrate bias makes the carbon networks in the films sp^2-like bonding states. The hardest a-C : N thin film showed a nanohardness greater than the TiN film which is widely used as hard coating materials. The nano-wear property was also investigated by Triboscope. After a region of 1μm x 1μm on the film surface was scanned by a Vercobich-type diamond tip in a low load, the wear depth of the region was observed by an atomic force microscope. The nano-wear property was much more excellent than that of the diamondlike carbon films which have been already applied as wear-resistant coatings. From these results, the a-C : N thin films synthesized in this study was proved to be useful in the fields related in tribology. Less