Effect of oxygen vacancy and zinc interstitial on the spontaneous polarization of wurtzite ZnO: maximally localized Wannier functions analysis

¹ Department of Applied Physics and the MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, P.R. China
² Department of Physics, Xi’an Jiaotong University City College, Xi’an, Shaanxi 710018, P.R. China

^a e-mail: hgye@mail.xjtu.edu.cn

Received: 7 February 2015
Revised: 29 March 2015
Accepted: 2 April 2015
Published online: 19 May 2015

Abstract

First-principles calculations are employed to obtain the maximally localized Wannier functions of wurtzite ZnO with O vacancy and Zn interstitial. Through analyzing the shape of Wannier functions and the distribution of Wannier function centers, the influence of O vacancy and Zn interstitial in different charge states on the spontaneous polarization are investigated. We found that polarization appears in 010 and [20] orientations when the defects are charged, and the absolute polarization value will get larger as the defect charge state increases. Neutral O vacancy decreases the spontaneous polarization along the [0 0 0 1] direction. For O vacancy in +1 and +2 charge states, an additional electronic field is introduced, and it results in a dramatic change in the electronic structure, which reverses the polarization. However, in the case of Zn interstitial in +2 charge state, we find that it is the ionic relaxation that plays a dominant role in the polarization reversal.