1. Electronic Materials Research Laboratory Key Laboratory of the Ministry of Education and International Center for Dielectric Research School of Electronic and Information Engineering Xi'an Jiaotong University Xi'an 710049 China
2. School of Materials Science and Engineering Shaanxi University of Science and Technology Xi'an 710021 China
3. Institute for Superconducting and Electronic Materials Australian Institute of Innovative Materials University of Wollongong NSW 2500 Australia