Tribological behaviors of oxygen-doped carbon coatings deposited by ion-irradiation-assisted growth

Abstract Oxygen-doped carbon coatings were deposited by ion-irradiation-assisted growth using an electron cyclotron resonance plasma processing system, and the effects of the O2 content on the coating's structure and tribological behavior were studied. During the coating deposition, O+, O2+, and Ar+ ions in the oxygen plasma were attracted to irradiate the growing coating surface, realizing oxygen plasma during-etching. X-ray photoelectron spectroscopy characterization showed that the O2 addition incorporated some oxygen atoms into the carbon coating, and the sp3/sp2 ratio of the entire coating increased. Such structural changes made the carbon coating present higher nanoscratch resistance and longer wear life that increased from 990 cycles to more than 5000 cycles. Finally, the reason why the oxygen doping can induce the sp3/sp2 ratio to increase was suggested to be ion-irradiation-induced chemical recombination energy release, which could only occur when the O2 introduction reduced the atom displacement threshold energy.