The structural and electrochemical properties of boron-doped nanocrystalline diamond thin-film electrodes grown from Ar-rich and H2-rich source gases

The microstructural, electrical and electrochemical properties of boron-doped (ultra)-nanocrystalline diamond (UNCD) films deposited from a CH4/H2/Ar source gas mixture were compared with those of boron-doped nanocrystalline diamond (NCD) films grown from a conventional CH4/H2 source gas mixture. Scanning electron microscopy, visible-Raman spectroscopy and X-ray diffraction analysis were employed to probe the film morphology and microstructure. Conducting-probe atomic force microscopy (CP-AFM) was used to simultaneously map the morphology and electrical conductivity of the two film types. Spatial heterogeneity in the electrical conductivity was observed for both films as each is composed of regions of high electrical conductivity isolated by more insulating regions. The electrochemical properties were evaluated using the redox couples: Fe(CN)63−/4−, Ru(NH3)63+/2+, IrCl62−/3−, methyl viologen, dopamine, and Fe3+/2+. Taken together, the results confirm that even though the morphology and microstructure of UNCD and NCD films are distinct, both boron-doped film types exhibit comparable electrical and electrochemical properties.