Tunable electrical resistivity of oxygen-deficient zinc oxide thin films

Abstract

Oxygen-deficient zinc oxide thin films were deposited by radio frequency magnetron sputtering with a sintered zinc oxide ceramic target under an atmosphere of manipulated sputtering gas pressure (SGP). Under the designed deposition conditions, all the prepared films were of hexagonal würtzite structure with c-axis as the preferential growth orientation. With increasing SGP, the film thickness, deposition rate, grain size and atomic ratio of O to Zn in the films initially increased and then decreased. Interestingly, when the SGP was low, the main defects in the films were oxygen vacancies; when it was high, the dominant defects were interstitial zinc; but when it was in a moderate value, the film composition might be relatively close to the stoichiometric ZnO, possessing the least number of defects. As a result, the electrical resistivity of the films first increased and then dropped down as the SGP increased.