1. State Key Laboratory of Environment-Friendly Energy Materials, Southwest University of Science and Technology, Mianyang 621010, People's Republic of China
2. School of Space Science and Physics, Shandong University, Weihai 264209, People's Republic of China
3. State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronics Science and Technology of China, Chengdu 610054, People's Republic of China