1. State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China
2. Micro & Nano Physics and Mechanics Research Laboratory, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China
3. Sino-French Institute of Nuclear Engineering and Technology, Zhuhai Campus, Sun Yat-sen University, Zhuhai 519082, P. R. China