1. SZU-NUS Collaborative Innovation Center for Optoelectronic Science & Technology, International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, People’s Republic of China
2. Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117551, Singapore
3. Department of Materials Science and Engineering, National University of Singapore, Singapore 117574, Singapore
4. College of Physics and Space Science, China West Normal University, Nanchong 637002, China
5. Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore 138634, Singapore
6. Centre for Advanced 2D Materials, National University of Singapore, Block S14, 6 Science Drive 2, Singapore 117546, Singapore