1. State Key Laboratory of Electronic Thin Film and Integrated Devices, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610054, P.R. China
2. College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, P.R. China
3. School of Materials and Energy, University of Electronic Science and Technology of China, Chengdu 610054, P.R. China