Electrical and mechanical properties of DLC coatings modified by plasma immersion ion implantation

DLC (a-C:H) films were deposited by the plasma enhanced chemical vapor deposition (PECVD) on silicon substrate and then post-implanted by plasma immersion ion implantation (PIII) at different voltages and ion species (Ar, N2 and C2H2). Microstructure, dielectric constant and nano-hardness of the modified DLC films were studied. It is found that implanted C2H2 ions can effectively increase the nano-hardness of DLC films from 13.5 to 25.3 GPa and reduce the dielectric constant to 2.5 in the bias voltage range of −35 to −40 kV. The improved properties are mainly associated with the increase in the ratio of sp3 CC/sp2 CC bonds and the reaction mechanisms in the implantation zone are discussed.