Capacitance-voltage measurements and flat-band potential determination on Zr-doped α-Fe 2O 3 single-crystal electrodes

Abstract

Capacitance-voltage measurements have been carried out on zirconium-doped α-Fe 2O 3 single-crystal electrodes. Two types of behaviour have been observed on the Mott-Schottky plots of the capacitance data. The first one occurs near the flat-band potential and has been attributed to a localized interface state. The second one is observed far from the flat-band potential and can be explained by a deep donor level. The energy, volume density and time constant of this level have been obtained from impedance measurements over a wide frequency range. Evidence for the deep level has also been found from a sub-band-gap photocurrent peak, and from the shift of the band-gap photocurrent onset with regard to the flat-band potential. The high volume density of this level suggests that it has to be treated as a narrow band that can be related to a crystal field level.