Structure and Properties of Nitrogen-Doped Hydrogenated Amorphous Carbon Films Fabricated by Plasma Immersion Ion Implantation (PIII)

Recently, carbon nitride films and amorphous carbon films have received much attention as potential biomedical materials. Plasma immersion ion implantation - deposition (PIII-D) is a novel surface modification method in the biomaterials field. Its major advantages are high efficiency and non line-of-sight characteristic and it is readily adapted to biomedical devices with complex shape. In this work, nitrogen-doped hydrogenated amorphous carbon (a-C:H:N) films were deposited by PIII-D using N₂/C₂H ₂ gas mixtures. Deposition was carried out at a constant RF power of 500 W. By adjusting the mix of N₂/C₂H₂, a series of a-C:H:N films with different nitrogen contents were obtained. The film chemistry was examined using micro-Raman, XPS and FTIR. The surface morphology of the films was characterized by atomic force microscopy (AFM), The wettability of the films was measured by contact angle measurements employing different well-known liquids. The corrosion resistance was evaluated using electrochemical analysis. The results show that the wettability and corrosion resistance of the films are enhanced with increasing nitrogen concentration in the films and higher nitrogen fraction in the gas that also affects the evolution of the film structure and chemical bonds caused by nitrogen doping. One of the important experimental observations is that incorporation of nitrogen into the sixfold carbon rings structure breaks the symmetry in the sp² domains.