Cyclic Voltammetric Studies of Charge Transfer Reactions at Highly Boron-Doped Polycrystalline Diamond Thin-Film Electrodes

Abstract

Cyclic voltammetry and ac impedance analysis were used to measure the background current response and capacitance of interfaces formed at as grown (untreated) boron-doped polycrystalline diamond thin-film electrodes in contact with aqueous electrolytes. The diamond films (∼1 cm 2 , 15 μm thick ; carrier concentration, ∼10 17 cm -3 ) were grown on conducting Si substrates by plasma-enhanced chemical vapor deposition. Cyclic voltammetry was also used to determine the charge transfer reactions of several redox analytes at as grown and chemically wet etched diamond thin-film electrodes and to study the effect of surface pretreatment, including Fe(CN) 6 3-/4- , IrCl 6 2-/3- , Ru(NH 3 ) 6 3+/2+ , dopamine, 4-methylcatechol, MV 2+/+/0 , and ferrocene. The electrochemical response exhibited by the films is explained using two models : (i) traditional electron transfer at a p-type semiconductor-electrolyte interface and (ii) electron transfer at a composite electrode composed of nondiamond carbon impurities contained within a diamond matrix such that k° nondiamond >> k° diamond.