1. School of Advanced Materials, Shenzhen Graduate School, Peking University, Shenzhen 518055, P. R. China
2. College of Engineering Physics, Shenzhen Technology University, Shenzhen 518118, P. R. China
3. State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-sen University, Guangzhou 510275, P. R. China
4. Department of Physics, Department of Materials Science and Engineering, and Department of Biomedical Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong P. R. China
5. Key Laboratory of Aerospace Information Materials and Physics, MIIT, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, P. R. China