Effects of platinum content on tribological properties of platinum/nitrogen doped diamond-like carbon thin films deposited via magnetron sputtering

Platinum (Pt) and nitrogen (N) were co-incorporated in diamond-like carbon (DLC) thin films using a magnetron sputtering system to form PtN-DLC thin films for tribological applications. The Pt content in the PtN-DLC films prepared on Si substrates was controlled by varying RF power applied to a Pt target at a fixed N2 flow rate. The tribological properties of the PtN-DLC films were investigated with respect to the Pt content in the films. The uncoated Si substrate surface tested against a steel ball of 6 mm in diameter had significant abrasive and fatigue wear, while no significant wear was found on the N-DLC coated sample surface, indicating that the N-DLC film effectively prevented its underlying Si substrate from wear. However, the incorporation of Pt in the N-DLC films reduced the wear resistance of the films by degrading sp3-bonded cross-linking structures of the films so that significant wear tracks were found on the surfaces of the PtN-DLC films. Therefore, the increased radio frequency (RF) power applied to the Pt target decreased the wear resistance of the PtN-DLC films as a result of the increased Pt content.