1. Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, Xi’an Jiaotong University, Xi’an 710049, Shaanxi, People’s Republic of China
2. Department of Materials Science and Engineering, University of Sheffield, Sheffield S1 3JD, U.K.
3. Institute
of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, People’s Republic of China
4. Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004, People’s Republic of China