1. Department of Physics and Astronomy, Aarhus University, 8000Aarhus C, Denmark
2. DTU Physics, Technical University of Denmark, 2800Kgs. Lyngby, Denmark
3. Center for Nanostructured Graphene, Technical University of Denmark, 2800Kgs. Lyngby, Denmark
4. Department of Materials and Production, Aalborg University, 9220Aalborg Øst, Denmark
5. Department of Mathematical Science, Aalborg University, 9220Aalborg Øst, Denmark
6. Center for Nanostructured Graphene (CNG), 9220Aalborg Øst, Denmark
7. Advanced Light Source, E. O. Lawrence Berkeley National Laboratory, Berkeley, California94720, United States
8. Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba305-0044, Japan
9. International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba305-0044, Japan
10. Department of Physics, Columbia University, New York, New York10027, United States