Effect of Oxygen Chemisorption and Photodesorption on the Conductivity of ZnO Powder Layers

Abstract

Chemisorption of oxygen on the surface of the grains of ZnO powder layers mainly controls the photoconductivity. The adsorption of oxygen ions is regarded as a chemical reaction at the interface and involves oxygen from the gas atmosphere and electrons from the metal oxide. The changes in the conductivity of ZnO-layers calculated on this basis are in fair agreement with the experimental results. At low light levels deviations from the theory are observed which result from an “ overdepletion ” of the conductivity controlling regions in the powder layer. Considering a ZnO layer as a secondary photoconductor has allowed the calculation of a maximum photosensitivity for such layers.