Investigation on the Nano-Friction Properties of Diamond-like Carbon Films

The diamond-like carbon (DLC) films are widely used as a protective coating layer in the magnetic storage systems and micro/nano-electro mechanical systems. However,the deficiency on the friction pairs' design of the DLC films has limited its practical application. Here,the Cr buffer layer was adopted and deposited on Si substrate to fabricate the DLC films by physical vapor deposition. By using the atomic force microscopy,the surface properties of the DLC films were characterized,and the effects of the mechanical properties of tip materials on the friction properties of the DLC films were also analyzed. Experimental results show that the friction force of the DLC films measured by Si tip and Si₃N₄ tip increased linearly with the normal force at nanoscale,which was irrelevant to tip materials. From the SEM image of Si tip,it is noted that the increase of the friction coefficient of Si/DLC friction pair was attributed to the wear of Si tip. From the AFM images of the DLC films,it is found that the increase of the friction coefficient of Si₃N₄/DLC is led by the plastic deformation of the asperities of the DLC films at high load. Finally,the experiment results are correspondingly matched to the theoretical calculation based on DMT model. Furthermore,this work provides a clue for the design of the friction pairs of the DLC films.