Characteristics of conductive amorphous carbon (a-C) films prepared by using the magnetron sputtering method

Abstract

It is possible to deposit films with very low resistivity (similar to 2 m Omega.cm) without any dopant. However, a main limitation in conductive amorphous carbon (a-C) for applications as electrodes is its poor adhesion to the substrate due to high residual stress. In this study, a-C films were deposited up to 200 nm in thickness on Si substrates by using a closed-field unbalanced magnetron sputtering method with a graphite target in an Ar atmosphere. And, the effects of various DC bias voltages from 0 V to -300 V and working pressures on the structure and the adhesion properties of the a-C films were investigated. This study focused on improving the physical properties of a-C film by controlling process parameters like the negative substrate DC bias voltage. The maximum hardness of the a-C films was 22 GPa, the friction coefficient was 0.1, and the critical load was 28.5 N on Si wafer. Also, the adhesion of the film increased and the compressive residual stress of the film increased with increasing DC bias voltage. The tribological properties of the a-C film showed a clear dependence on the energy of ion bombardment and the density of the sputtering gas during film growth.