1. Department of Physics and Astronomy & National Graphene Institute, The University of Manchester, Manchester M13 9PL, United Kingdom
2. State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, China
3. Department of Physics, Indian Institute of Technology Gandhinagar, Gujarat 382355, India
4. Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
5. Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain
6. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
7. Institute of Physical Chemistry and Center for Energy and Environmental Chemistry Jena (CEEC Jena), Friedrich Schiller University Jena, 07743 Jena, Germany
8. Central Facility for Electron Microscopy, Electron Microscopy Group of Materials Science, Ulm University, Ulm 89081, Germany
9. Department of Physics, Department of Materials Science and Engineering & Centre for Advanced 2D Materials, National University of Singapore, Singapore 119260
10. National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan & Department of Mechanical Engineering, The University of Tokyo, Bunkyo City, Tokyo 100-8921, Japan
11. Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
12. Shenzhen Graphene Center, Tsinghua-Berkeley Shenzhen Institute, Tsinghua University, Shenzhen 518055, China