1. Department of Physics The University of Hong Kong Hong Kong 999077 P. R. China
2. Hubei Yangtze Memory Laboratories Wuhan 430205 China
3. Faculty of Physics and Electronic Science and School of Microelectronics Hubei University Wuhan 430062 China
4. MIIT Key Laboratory of Advanced Display Materials and Devices Institute of Optoelectronics & Nanomaterials School of Materials Science and Engineering Nanjing University of Science and Technology Nanjing 210094 China
5. Engineering Research Center of Nano‐Geomaterials of Ministry of Education Faculty of Materials Science and Chemistry China University of Geosciences Wuhan 43007 China
6. Institute of Applied Physics and Materials Engineering University of Macau Macau 999078 China