1. Department
of Chemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore
2. Department of Physics, National University of Singapore, 2 Science
Drive 3, 117542, Singapore
3. Hefei National Laboratory for Physical Sciences at the Microscale, CAS Centre for Excellence and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei 230026, China
4. Center for Advanced 2D Materials and Graphene Research
Center, National University of Singapore, 3 Science Drive 3, 117546, Singapore
5. Guizhou Provincial Key Laboratory of Computational Nano-Material
Science, Guizhou Normal College, Guiyang 550018, China
6. National University of Singapore (Suzhou) Research Institute, 377 Lin Quan Street, Suzhou Industrial Park, Jiang Su 215123, China