The Structure and Electrochemical Behavior of Nitrogen-Containing Nanocrystalline Diamond Films Deposited from CH4/N2/Ar Mixtures

Abstract

Electrically conductive nanocrystalline diamond films (approximately 750 to 1000 nm thick) were deposited on conducting Si and W substrates from gas mixtures using plasma-enhanced chemical vapor deposition. Such films are continuous over the surface and nanometer smooth. The grain size is 3 to 10 nm, and the grain boundaries are 0.2 to 0.5 nm wide (two carbon atoms). Nitrogen appears to substitutionally insert into the grain boundaries and the film concentration scales with the added to the source gas mixture up to about the 5% level. The nitrogen-incorporated films are void of pinholes and cracks, and electrically conducting due in part to the high concentration of nitrogen impurities and or the nitrogen-related defects bonding). The films possess semimetallic electronic properties over a potential range from at least −1.5 to 1.0 V vs. SCE. The electrodes, like boron-doped microcrystalline diamond, exhibit a wide working potential window, a low background current, and high degree of electrochemical activity for redox systems such as and methyl viologen More sluggish electrode kinetics are observed for 4-methylcatechol, presumably due to weak adsorption on the surface. Apparent heterogeneous electron transfer rate constants of to are observed for and at films without any pretreatment. © 2000 The Electrochemical Society. All rights reserved.