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.

Keywords:

• Oxygen-deficient zinc oxide
• Thin film
• RF magnetron sputtering
• Sputtering gas pressure
• Electrical resistivity

Acknowledgements

The authors would like to thank the financial support for this work from the National Natural Science Foundation of China (grant nos. 61274015, 11274052 and 51172030), and Excellent Adviser Foundation in China University of Geosciences from the Fundamental Research Funds for the Central Universities.