Study of mechanical properties and stress of tetrahedral amorphous carbon films prepared by pulse biasing

Tetrahedral amorphous carbon (ta-C) films have been deposited by filtered cathodic vacuum arc technique with substrate pulse bias ranging from −100 to −3000 V. The surface morphology, structure, stress, hardness and Young's modulus of the films were characterized using atomic force microscopy, Raman spectroscopy, surface profilometry and nanoindentation. The results show that the highest stress existed at the pulse bias voltage between −100 and −200 V. The mechanical properties of the films were determined directly from an Oliver-Pharr analysis of nanoindention experimental data. The highest hardness and reduced Young's modulus, which were achieved at −200 V, were 85 and 390 GPa, respectively. By using the relationship between hardness and stress, 1-μm-thick ta-C films were successfully deposited using −2000 V with a moderate hardness of about 36 GPa and a low stress of less than 1 GPa.