Development of the carbon thin films nanostructured by femtosecond laser pulse with a super low friction coefficient and local conductivity

本文报道了用飞秒激光脉冲对类金刚石（DLC）薄膜表面进行纳米化处理后的摩擦学性能。利用为光纤激光加工而开发的精确目标扫描系统，对DLC表面的广阔区域进行了纳米结构处理。在本实验中，我们研制了两种类型的激光扫描。一种是平行扫描，以产生均匀的纳米结构表面。另一种是沿着网状图案进行交叉扫描，在表面形成部分纳米结构区域。所得结果总结如下：1)在DLC表面15 × 15 mm^2.2的面积上形成了均匀的纳米结构。在E=110μJ的烧蚀阈值附近的结构表面均匀地修饰为气相色谱层。3)结构DLC膜的摩擦系数对钢球有较小的减小，而陶瓷WC-Co球有较小的增大。4)在纳米结构的DLC表面涂覆MoS2层，使DLC表面的摩擦系数有了较大的提高。钢球表面实测摩擦系数μ为0.07，WC-Co球表面实测摩擦系数μ为0.02 ~ 0.04。5)交叉扫描产生的烧蚀区网状图案是增加保持初始表面平整度的有效方法。6)纳米压痕测试和纳米划痕测试（100 ~ 2000μN）表明，与未处理的DLC相比，激光处理后的GC表面层变得柔软，摩擦系数增加。

We report tribological properties of diamond-like carbon (DLC) film of which surface has been nanostructured with femtosecond (fs) laser pulses. A broad area on the DLC surface was nanostructured using a precise target-scan system developed for the fs-laser processing. In the present experiment we have developed two types of laser scan. One is a parallel scan to produce a uniformly nanostructured surface. The other is a crossed scan along a net-like pattern to form a partially nanostructured area on the surface. The results obtained are summarized as follows.1) The nanostructure has been formed uniformly on the DLC surface over the area of 15 x 15 mm^2.2) The structured surface at E=110μJ near the ablation threshold is uniformly modified to the GC layer.3) The friction coefficient of the structured DLC film has shown a small decrease for the steel ball but a small increase for the ceramic WC-Co ball.4) A large improvement of the friction coefficient of the DLC surface has been achieved by coating the MoS2 layer on the nanostructured DLC surface. The measured friction coefficients μ of the surface were 0.07 with the steel ball and 0.02-0.04 with the WC-Co ball.5) The net-like patterning of the ablated zone created by the crossed scan produces an effective method to increase maintaining the initial surface flatness.6) The nano-indentation test and nano-scratch test (100〜2000μN) indicate that the laser-treated surface layer modified to GC becomes soft and its friction coefficient increases as compared with that of the untreated DLC.