Electron spin resonance investigation of electrical conductivity parameters of zinc oxide during surface reactions

Abstract

The effect of the electron transfer process between the bulk and surface of ZnO upon oxygen sorption was investigated by measuring the changes of the following ESR parameters: the spin densities of the g = 1.96 and g ~ 2.0 signals, the intensity of a Mn 2+ reference sample, and the crystal current of the microwave detector. The approach was also used to investigate the relative density of conduction electrons in mixtures of copper in ZnO. A theory was developed to show that these ESR parameters may be used to describe the density of electrons in the conduction band of ZnO, and the theory was applied to the results of oxygen sorption on ZnO. Evidence is presented which shows that the g = 1.96 signal of ZnO should probably be assigned to electrons in the conduction band and not to electrons in donor states. Application of this ESR approach in investigations of heterogeneous catalysis, particularly oxidation reactions, is discussed.