Effect of deposition voltage on the microstructure of electrochemically deposited hydrogenated amorphous carbon films

Hydrogenated amorphous carbon (a-C:H) films were deposited on Si substrates by electrolysis in a methanol solution at ambient pressure and a low temperature (50 °C), using various deposition voltages. The influence of deposition voltage on the microstructure of the resulting films was analyzed by visible Raman spectroscopy at 514.5 nm and X-ray photoelectron spectroscopy (XPS). The contents of sp 3 bonded carbon in the various films were obtained by the curve fitting technique to the C1s peak in the XPS spectra. The hardness and Young’s modulus of the a-C:H films were determined using a nanoindenter. The Raman characteristics suggest an increase of the ratio of sp 3/sp 2 bonded carbon with increasing deposition voltage. The percentage of sp 3-bonded carbon is determined as 33–55% obtained from XPS. Corresponding to the increase of sp 3/sp 2, the hardness and Young’s modulus of the films both increase as the deposition voltage increases from 800 V to 1600 V.