1. Multifunctional Materials and Structures Key Laboratory of the Ministry of Education & International Center for Dielectric Research School of Electronic Science and Engineering Xi'an Jiaotong University Xi'an 710049 P. R. China
2. School of Electronic and Information Engineering Xi'an Jiaotong University Xi'an 710049 P. R. China
3. Information Materials and Devices Research Center Shanghai Institute of Ceramics Chinese Academy of Science 585 Heshuo Road Shanghai 201899 P. R. China
4. School of Electronic and Information Engineering Hangzhou Dianzi University Hangzhou 310018 P. R. China
5. School of Material Science and Energy Engineering Foshan University Foshan Guangdong 528000 P. R. China