Charge fields in Bi12GeO20 and dynamic flat-band potentials

Abstract

A Bi12GeO20 single crystal was used to construct a photoelectrochemical memory using an aqueous junction. Two kinds of charge fields were observed, the first being of opposed polarity to the applied field in the stable condition, the second situated 0.20 and 0.33 eV above the valence band and in the stable condition with the same polarity as the applied field. The flat-band level at no charge is −250 mV versus SCE at pH=6.9 with −50±5 mV/pH. The presence of charge fields changes the Fermi level in both directions, so that under dynamic conditions a maximum of four different flat-band potentials can be observed. Additional information is given on charge-field processes observed by other authors.