1. National Engineering
Research Center of Electromagnetic Radiation Control Materials and
State Key Laboratory of Electronic Thin Films and Integrated Devices,
School of Microelectronics and Solid State Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China
2. Department
of Chemistry and Centre for Advanced 2D Materials and Graphene Research
Centre, National University of Singapore, 3 Science Drive 3, Singapore 117543
3. IBM, Malta, New York 12020, United States
4. State
Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
5. Department of Physics, Colorado State University, Fort
Collins, Colorado 80523, United States