1. Department of Optoelectronic, Xiamen University of Technology, Xiamen, Fujian 361024, China
2. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
3. Department of Physics and Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
4. Beijing Key Laboratory for Advanced Functional Materials and Structure Research, Beijing 100190, China
5. Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
6. Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565, Japan