1. Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, Shaanxi China
2. Materials Science and Engineering, University of Sheffield, S1 3JD Sheffield, U.K.
3. Micro-optoelectronic Systems Laboratories, Xi’an Technological University, Xi’an 710032, Shaanxi China