Influence of UV irradiation in low frictional performance of CN x coatings

The influence of ultraviolet (UV) irradiation on low frictional performance of CN x coatings with 100 nm thickness having nitrogen contents of 9%, 14% and 19% deposited on Si(100) substrate by ion beam mixing was investigated in N 2 atmosphere environment. Three UV lights of 254, 312 and 365 nm were used to irradiate the surface of CN x  / Si(100) for 60 min. The changes of N / C ratio and atomic binding energy in the coating were analysed using Auger electron spectroscopy and X‐ray photoelectron spectroscopy, respectively. The friction coefficient of Si 3 N 4 ball sliding against CN x was measured by a pin‐on‐disc tribometer, and wear tracks were analysed by the transmission electron microscope image. The results showed that UV irradiation on CN x coating can decrease the critical frictional cycles for low friction coefficient and that the mechanism is due to the formation of graphite‐like structure in the topmost CN x coating. Copyright © 2012 John Wiley & Sons, Ltd.