ELECTRON CAPTURE BY IONS AT ZNO/SOLUTION INTERFACE

The electron reactivity (electron capture rate) of one-equivalent oxidizing agents at the ZnO surface is determined by cathodic electrochemical reduction. Because in this system the Helmholtz potential is insensitive to the oxidizing agent used, the energy level of a particular species with respect to the ZnO conduction band is not considered a variable Thus the electron capture by (reduction of) the species can be interpreted according to surface state capture theory. The energy levels are estimated by analysis of the redox potential of the species. A maximum in electron reactivity is found for energy levels just below the conduction band minimum, the reactivity decreasing rapidly for higher energy levels. There is some indication that the electron reactivity decreases for very low energy levels, in accordance with expectations if the process is controlled by a multi-phonon electron capture model. © 1969.