The Structure and Electrochemical Behavior of Nitrogen-Containing Nanocrystalline Diamond Films Deposited from CH[sub 4]/N[sub 2]/Ar Mixtures

Publisher Website
Google Scholar
Abstract
Electrically conductive nanocrystalline diamond films (approximately 750 to 1000 nm thick) were deposited on conducting Si and W substrates from CH4/N2/ArCH4/N2/Ar 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 (∼1020 atom/cm3)(∼1020 atom/cm3) scales with the N2N2 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 (sp2(sp2 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 Fe(CN)6−3/−4,Fe(CN)6−3/−4, Ru(NH3)6+3/+2,Ru(NH3)6+3/+2, IrCl6−2/−3,IrCl6−2/−3, and methyl viologen (MV+2/+).(MV+2/+). More sluggish electrode kinetics are observed for 4-methylcatechol, presumably due to weak adsorption on the surface. Apparent heterogeneous electron transfer rate constants of 10−210−2 to 10−1 cm/s10−1 cm/s are observed for Fe(CN)6−3/−4,Fe(CN)6−3/−4, Ru(NH3)6+3/+2,Ru(NH3)6+3/+2, IrCl6−2/−3,IrCl6−2/−3, and MV+2/+MV+2/+ at films without any pretreatment. © 2000 The Electrochemical Society. All rights reserved.