The Basic Electrochemical Properties and Structure of Direct Current Magnetron Sputtered Carbon Films

In recent years, carbon films have attracted interest as electrode materials for electrochemical sensors due to their wide potential window and acceptable electrochemical activity. The films can be fabricated into electrodes of any shape and size. The electrochemical performance of the films depends on their structural features such as the ratio of the sp2 and sp3 bonds, and the surface functional groups. Here, we report the control of both structure and electrochemical properties based on carbon films fabricated by easily available direct current (DC) magnetron sputtering equipment. The sp3 concentration (sp3/sp3 + sp2) can be controlled from 0.22 to 0.29 by changing the substrate bias power, which can be characterized with X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The potential window became wider as the sp3 concentration increased, similar to the results we previously obtained with films formed by unbalanced magnetron (UBM) sputtering. The electrochemical properties of DC magnetron sputtered carbon films were examined with four species, namely Ru(NH3)62+/3+, Fe(CN)63−/4−, Fe2+/3+, and dopamine. The peak separation of these species depended on the content of the edge plane of the film for Fe(CN)63−/4− and surface functional groups containing oxygen for Fe2+/3+, and both edge plane and surface oxygen-containing groups for dopamine. These results indicate that our carbon films perform sufficiently well for use in electroanalysis and are not inferior to previously reported carbon film electrodes.