Synthetic semiconductor diamond electrodes: Electrochemical behaviour of homoepitaxial boron-doped films orientated as (1 1 1), (1 1 0), and (1 0 0) faces

Electrode behavior of homoepitaxial (single-crystal) boron-doped diamond films deposited onto differently orientated faces of dielectric diamond single crystals is studied by the electrochemical impedance and potentiodynamic curves methods. For the films grown under constant concentration of the volatile boron compound in the feeding gas, the rate of electrode reactions in the [Fe(CN)6]3−/4− and [Ru(NH3)6]2+/3+ redox systems decreases in the series: (1 1 1) → (1 1 0) → (1 0 0)-face. It is shown that the acceptor concentration (estimated from the slope of Mott–Schottky plots) also decreases in the above-given series. This is explained by the different intensity of boron incorporation into differently orientated faces of the diamond crystals during their growth. Thus, the apparent dependence of the electrochemical reaction rate on the crystal face orientation can be reduced to the earlier found interrelationship between the electrochemical kinetics at diamond electrodes and their doping level. By contrast, for the films grown under different boron concentration in the feeding gas, chosen in such a way that the acceptor concentration in the differently orientated diamond films is nearly the same, no significant difference in the kinetic behavior was found between the (equally doped) (1 1 1)- and (1 0 0)-faces.