Study of facing target sputtered diamond-like carbon overcoats for hard disk drive media

• Facing target sputtered (FTS) diamond-like carbon (DLC) samples were studied.
• FTS DLC samples possess higher density and hardness.
• Surface conditions and flyability performances for FTS DLC samples were comparable.
• Wear tests on FTS DLC samples showed lower media wear, but higher head wear.

The demand for higher areal density in the hard disk drive industry has fuelled extensive research efforts and focuses on magnetic spacing reduction. In the head–disk interface arena, one of the key focuses is to reduce the carbon overcoat thickness without compromising the overcoat protection performance. Thus, in the search for alternative methods to reduce the carbon overcoat thickness, the facing target sputtering (FTS) process for diamond-like carbon deposition has been investigated. The resulting properties have been presented in this paper, with comparison to conventional diamond-like carbon (DLC) layers by other processes such as chemical vapor deposition and reactive sputtering with nitrogen. X-ray reflectometry results showed that facing target sputtered DLC samples displayed significantly higher density, at 2.87 g/cm3, as compared to hydrogenated and nitrogenated DLC samples. This was attributed to the higher sp3 content, as obtained by X-ray photoelectron spectroscopy measurements. As a result of the high sp3 content, hardness of the FTS deposited samples was higher than that of the hydrogenated and nitrogenated DLC samples. In addition, the surface energy of FTS samples was observed to be comparable, but lower, than that of nitrogenated DLC samples through contact angle measurements. Clearances comparable to that of conventional DLC samples were achieved and the sample disks were flyable. Wear performance tests also revealed more wear resistance for the FTS deposited DLC samples, but also higher head wear.