Band and hopping conduction in high-resistivity ZnO

Abstract

We have measured the complex dielectric function of sputtered ZnO films over a wide frequency range (10-2-107 Hz) and over a temperature range extending from -60 to 100°C. A detailed examination of these results reveals the contributions of band conduction and hopping conduction to the dielectric dispersion. In certain cases, contact polarization effects gave an additional contribution at the lowest frequencies. A microscopic model for the conduction is proposed in which singly charged oxygen-vacancy sites are in communication with one another by way of the conduction band. Quantitative evaluation of the data are in support of this model.