Understanding the Role of Nitrogen in Plasma-Assisted Surface Modification of Magnetic Recording Media with and without Ultrathin Carbon Overcoats

A novel scheme of pre-surface modification of media using mixed argon-nitrogen plasma is proposed to improve the protection performance of 1.5 nm carbon overcoats (COC) on media produced by a facile pulsed DC sputtering technique. We observe stable and lower friction, higher wear resistance, higher oxidation resistance, and lower surface polarity for the media sample modified in 70%Ar + 30%N(2) plasma and possessing 1.5 nm COC as compared to samples prepared using gaseous compositions of 100%Ar and 50%Ar + 50%N(2) with 1.5 nm COC. Raman and X-ray photoelectron spectroscopy results suggest that the surface modification process does not affect the microstructure of the grown COC. Instead, the improved tribological, corrosion-resistant and oxidation-resistant characteristics after 70%Ar + 30%N(2) plasma-assisted modification can be attributed to, firstly, the enrichment in surface and interfacial bonding, leading to interfacial strength, and secondly, more effective removal of ambient oxygen from the media surface, leading to stronger adhesion of the COC with media, reduction of media corrosion and oxidation, and surface polarity. Moreover, the tribological, corrosion and surface properties of mixed Ar + N(2) plasma treated media with 1.5 nm COCs are found to be comparable or better than ~2.7 nm thick conventional COC in commercial media.