Direct and surface state mediated electron transfer at semiconductor/electrolyte junctions .2. A comparison of the interfacial admittance

The interfacial electrical admittance of a semiconductor electrode exchanging majority carriers with a simple redox system is calculated from basic assumptions presented in a previous paper. Direct exchange and surface state mediated exchange are considered. The coupling between the occupancy of the surface states and the distribution of the interfacial potential drop over the depletion and Helmholtz-layers is taken into account quantitatively using the fluctuating energy level model. The results show that direct and surface state mediated transfer can be distinguished on the basis of the electrical admittance. Some simple, but important, cases of surface state mediated exchange are reviewed in the framework of the model. The consequences of the coupling between the occupancy of the surface states and the distribution of the interfacial potential drop over depletion and Helmholtz-layer are discussed in detail. Copyright (C) 1997 Elsevier Science Ltd.