Enhanced characteristics of pulsed DC sputtered ultrathin (< 2 nm) amorphous carbon overcoats on hard disk magnetic media

• 1.5 nm thick pulsed DC (PDC) sputtered carbon overcoats (COCs) were prepared.
• PDC sputtered COC showed lower friction than continuous DC (CDC) sputtered COC.
• PDC sputtered COC showed higher oxidation resistance than CDC sputtered COC.
• PDC COC also showed comparable tribological performance with thick commercial COC.
• PDC sputtered COC showed ~ 26% higher sp3 bonding than CDC sputtered COC.

We report on the unusual tribological, surface and corrosion properties of ultrathin (~ 1.5 nm) amorphous carbon (a-C) overcoats, which have been grown on CoCrPt:oxide-based media using a facile pulsed direct current (DC) sputtering process. The a-C films produced by pulsed DC sputtering are found to show low surface roughness (~ 1.5 Å), low coefficient of friction (COF, between 0.2 and 0.3), high wear resistance and higher corrosion/oxidation resistance. The in-depth spectroscopic analyses by X-ray photoelectron spectroscopy, micro-Raman, and time of flight-secondary ion mass spectroscopy support our findings. The properties of pulsed DC sputtered carbon are also compared with those of continuous DC sputtered carbon of the same thickness and are found to be superior. In addition, the tribological results of pulsed DC sputtered carbon are found to be comparable with commercial media of total overcoat thickness of ~ 3.7 nm (~ 2.7 nm carbon overcoat and ~ 1 nm lubricant). These results are important in view of developing ultrathin yet protective coating by facile approach for hard disk media overcoat application.