Intrinsic mechanical properties of diamond-like carbon thin films deposited by filtered cathodic vacuum arc

The mechanical properties—Young’s modulus (E) and hardness (H)—of diamond-like carbon (DLC) thin films deposited on $p2+$ Si (100) by filtered cathodic vacuum arc with different substrate bias voltage have been studied by nanoindentation measurement, where the substrate effect is included. Their intrinsic properties [including E,H, and yield strength (Y)] without the substrate effect are then derived by finite element analysis. The results show that the intrinsic mechanical properties of the DLC thin films are not affected by the film thickness, but significantly affected by change of $sp3$ bonding fraction caused by varied substrate bias. An empirical relationship among E, Y, and H for DLC thin films has been built, where E, Y, and H are intrinsic properties of DLC thin films. It is also confirmed that, as an empirical rule, the measured H could be used to represent its intrinsic value when the indentation depth is limited to 10% of the film thickness. However, the measured E with the substrate effect does not observe this empirical rule.