Structure and Property of Diamond-like Carbon Coating with Si and O Co-Doping Deposited by Reactive Magnetron Sputtering

In this paper, diamond-like carbon (DLC) coatings with Si and O co-doping (Si/O-DLC) were deposited by reactive magnetron sputtering using a gas mixture of C2H2, O-2 and Ar to sputter a silicon/graphite splicing target. The O content in the Si/O-DLC coatings was controlled by tuning the O-2 flux in the gas mixture. The composition, chemical bond structure, mechanical properties and tribological behavior of the coatings were investigated by X-ray photoelectron spectroscopy, Fourier infrared spectrometer, Raman spectroscopy, nanoindentation, a scratch tester and a ball-on-disk tribometer. The electrical resistivity of the Si/O-DLC coatings was also studied using the four-point probe method. The results show that the doping O tends to bond with Si to form a silicon-oxygen compound, causing a decrease in the sp(3) content as well as the hardness of the coatings. The tribological performance of the coatings can be improved due to the formation of the silicon-oxygen compound, which can effectively reduce the friction coefficient. In addition, the insulating silicon-oxygen compound is doped into the C-C network structure, significantly improving the surface resistivity of the DLC coating with a low sp(3) content. The Si/O-DLC coatings with good mechanical properties, tribological performance and electrical insulation properties might be used as protection and insulation layers for microelectronics.