1. Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore
2. Department of Physics, Applied Physics & Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
3. Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha 410082, China
4. Center for Advanced 2D Materials, National University of Singapore, 117546, Singapore
5. State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Chinese Academy of Sciences, No. 3888 Dongnanhu Road, Changchun 130033, China
6. School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
7. State Key Laboratory of High Performance Ceramics and Superfine, Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201899, China
8. Key Laboratory of Resource Chemistry of Ministry of Education, College of Chemistry and Materials Science, Shanghai Normal University, Shanghai 200234, China
9. Department of Physics, National University of Singapore, 2 Science Drive 3, 117542, Singapore
10. Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou 350207, China