Electrochemical properties of N-doped hydrogenated amorphous carbon films fabricated by plasma-enhanced chemical vapor deposition methods

Nitrogen-doped hydrogenated amorphous carbon thin films (a-C:N:H, N-doped DLC) were synthesized with microwave-assisted plasma-enhanced chemical vapor deposition widely used for DLC coating such as the inner surface of PET bottles. The electrochemical properties of N-doped DLC surfaces that can be useful in the application as an electrochemical sensor were investigated. N-doped DLC was easily fabricated using the vapor of nitrogen contained hydrocarbon as carbon and nitrogen source. A N/C ratio of resulting N-doped DLC films was 0.08 and atomic ratio of sp 3/ sp 2-bonded carbons was 25/75. The electrical resistivity and optical gap were 0.695 Ω cm and 0.38 eV, respectively. N-doped DLC thin film was found to be an ideal polarizable electrode material with physical stability and chemical inertness. The film has a wide working potential range over 3 V, low double-layer capacitance, and high resistance to electrochemically induced corrosion in strong acid media, which were the same level as those for boron-doped diamond (BDD). The charge transfer rates for the inorganic redox species, Fe 2+/3+ and Fe(CN) 6 4−/3− at N-doped DLC were sufficiently high. The redox reaction of Ce 2+/3+ with standard potential higher than H 2O/O 2 were observed due to the wider potential window. At N-doped DLC, the change of the kinetics of Fe(CN) 6 3−/4− by surface oxidation is different from that at BDD. The rate of Fe(CN) 6 3−/4− was not varied before and after oxidative treatment on N-doped DLC includes sp 2 carbons, which indicates high durability of the electrochemical activity against surface oxidation.