Nanoindentation-induced deformation behaviors of tetrahedral amorphous carbon film deposited by cathodic vacuum arc with different substrate bias voltages

Abstract

The diamond-like carbon (DLC) thin films were deposited using a direct cathode vacuum arc (DCVA) technology at a variety of substrate bias voltages from 0 to −50 V. The cross-sectional morphologies, compositions, chemical state, and surface roughness of the prepared DLC films were investigated and highly controlled by the bias voltage. The detailed microstructure of the DLC films and interfaces were observed by transmission electron microscope (TEM). The mechanical properties of the DLC films were obtained by nano-indentation test and significantly depended on the applied bias voltages. The deformation mechanisms and crack initiation/propagation of the DLC films at different substrate bias voltage (SBV) in the nano-indentation process were analyzed by TEM and clarified by evolution models. There were three forms to release the energy induced by indenter for the DLC films with an amorphous structure, as follows: (i) the plastic deformation stemmed from the flow of a large number of C atoms; (ii) the formation and slip of the shear bands; (iii) the cracking at the position of stress concentration.