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. Micro-optoelectronic Systems Laboratories, Xi’an Technological University, Xi’an 710032, Shaanxi, People’s Republic of China
3. National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, Anhui, People’s Republic of China