1. Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
2. CINTRA UMI CNRS/NTU/THALES, Singapore 637553, Singapore
3. School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
4. Energy Research Institute@NTU (ERI@N), Nanyang Technological University, Singapore 637553, Singapore
5. Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, Singapore 117603, Singapore
6. NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117456, Singapore
7. Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore
8. NUSNNI-NanoCore, National University of Singapore, Singapore 117411, Singapore