Tribological Behavior of Amorphous Carbon Nitride Overcoats for Magnetic Thin-Film Rigid Disks

Abstract

Amorphous carbon nitride coatings of thickness of 5 and 30 nm were deposited onto 65 and 95 mm magnetic thin-film rigid disks surfaces using single-cathode and dual-cathode magnetron sputtering systems containing nitrogen-argon plasmas. Under optimum deposition conditions, amorphous carbon nitride coatings can be synthesized on ultrasmooth thin-film disks with no significant pinholes at thickness down to 5 nm, with hardness 22–28 GPa (compared to 7–12 GPa for amorphous carbon), and r.m.s. roughness as low as 0.25 nm. These amorphous carbon nitride coatings were shown to have better contact-start-stop performance and three-to-four times better pin-on-disk contact durability compared with amorphous carbon overcoats under identical testing conditions. Amorphous carbon nitride appears to be a promising candidate overcoat material for replacing amorphous carbon in the next-generation magnetic thin-film rigid disk systems.

Mechanical properties of amorphous carbon nitride thin films prepared by reactive magnetron sputter-deposition

“…We showed that these CNx films achieve wear rates 3-4 times lower than those of amorphous carbon films tested under similar conditions [26], suggesting that CNx can potentially be a replacement overcoat material for next-generation computer disk surfaces. High level compressive stress may be needed to make metastable crystalline ~I-C3N4.…”

Thermal expansion dependence on the sp2 concentration of amorphous carbon and carbon nitride

“…Unfortunately, high concentration of nitrogen is very difficult to achieve. However, films with small concentration of nitrogen have shown some interesting tribological properties [4,5]. Indeed, amorphous carbon nitride is presently used as a protective coating in hard disks and read heads [5,6].…”

Application of cathodic arc deposited amorphous hard carbon films to the head/disk tribology

“…These films show the highest sp3 fraction for hydrogenated films of 75%, a hardness of 60 GPa, and a mass density of 2.9 g/cm3. Hydrogen and nitrogen containing films deposited by other methods such as variations of the sputter technique and plasma enhanced CVD have a lower sp3 fraction around 20-40%, a hardness of 15-35 GPa, an elastic modulus of 100-200 GPa, a mass density of 1.7-2.3 g/cm3, and a stress of 1-3 GPa [16,18,[19][20][21]25,26].…”