1. Department
of Chemistry and Centre for Advanced 2D Materials and Graphene Research
Centre, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
2. National
Engineering Research Center of Electromagnetic Radiation Control Materials
and State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
3. School of Physical & Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
4. China Academy of Engineering Physics, P.O.
Box 919-71, Mianyang, 621900, Sichuan, China
5. CAS Center for Excellence in Nanoscience & CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Center for Nanoscience and Technology, Beijing 100190, China