1. Institute for Manufacturing, Department of Engineering, University of Cambridge, 17 Charles Babbage Rd, Cambridge CB3 0FS, UK
2. Cavendish Laboratory, Department of Physics, University of Cambridge, 17 JJ Thomson Ave, Cambridge, CB3 0HE, UK
3. Cambridge Graphene Centre, Department of Engineering, University of Cambridge, 9 JJ Thomson Ave, Cambridge, CB3 0HE, UK
4. Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
5. Department Chemie, Universität Paderborn, 33098 Paderborn, Germany
6. SSRL Materials Science Division, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
7. Rowland Institute, Harvard University, Cambridge, Massachusetts 02142, USA
8. Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg