Effects of deposition pressure on microstructure and tribological properties of pulsed laser deposited CNx films

The CNx films were deposited on monocrystal silicon substrates by pulsed laser ablation of CNx target under the nitrogen gas pressure ranging from 2 Pa to 11 Pa. The chemical composition, bonding properties and surface morphology of the CNx films are investigated by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and scanning electron microscopy (SEM), respectively. Meanwhile, the tribological properties of the films are tested by using a ball-on-disk tribometer. The results show that low deposition pressure could degrade the nitrogen content and wear resistance of the pulse laser deposited CNx films. In the range of deposition pressure from 5 Pa to 8 Pa, it is good for the formation of the sp3 hybrid bonding but the nitrogen content decreases gradually. A decreased ratio of xsp2/xsp3 and ID/IG, an increased ratio of xspC-N2/ xspC-N3 and a good wear resistance at the order of (2.7-4.3) × 10-15&middotm3 &middot N-1&middotm-1 but a higher friction coefficient about 0.24-0.25 are observed under the deposition pressure ranging from 5 Pa to 8 Pa. Further increase in deposition pressure leads to the decrease of N content and an increased degree of graphitization, the friction coefficient of the film is around 0.19, and a worse wear resistance is found.