1. International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of Education, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen 518060, P.R. China
2. Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P.R. China
3. Department of Physics, Faculty of Science, National University of Singapore, 117542 Singapore
4. Singapore Synchrotron Light Source (SSLS), National University of Singapore, 117542 Singapore
5. Institute of Chemical and Engineering Sciences, A*STAR, 1 Pesek Road, Jurong Island, 627833 Singapore