* Corresponding authors

^a Cambridge Graphene Centre, University of Cambridge, Cambridge, UK
E-mail: acf26@eng.cam.ac.uk

^b Istituto Italiano di Tecnologia, Graphene Labs, Genova, Italy

^c Department of Physics, Lancaster University, Lancaster, UK

^d School of Physics and Astronomy, University of Manchester, Manchester, UK

^e ICN2-Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Barcelona), Spain

^f Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain

^g Centre for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology, Technical University of Denmark, Lyngby, Denmark

^h Nokia Technologies, Broers Building, Cambridge, UK

ⁱ Institut de Ciències Fotòniques (ICFO), Castelldefels (Barcelona), Spain

^j CNR-Istituto per la Sintesi Organica e la Fotoreattività, Bologna, Italy

^k Dipartimento di Ingegneria Civile, Ambientale e Meccanica, Università di Trento, Trento, Italy

^l Fondazione Bruno Kessler, Trento, Italy

^m School of Engineering and Materials Science, Queen Mary University of London, London, UK

ⁿ Walter Schottky Institut, Technische Universität München, Garching, Germany

^o L-NESS, Dipartimento di Fisica, Politecnico di Milano, Como, Italy

^p CNRS, Institut de Biologie Moléculaire et Cellulaire, Immunopathologie et Chimie Thérapeutique, 67000 Strasbourg, France

^q Centre for Neuroscience (BRAIN) and Dipartimento di Scienze della Vita, Università di Trieste, Trieste, Italy

^r Dipartimento di Scienze Farmaceutiche, Università di Trieste, Trieste, Italy

^s Department of Materials Science and Engineering, University of Ioannina, Ioannina, Greece

^t Applied Graphene Materials, The Wilton Centre, Redcar, Cleveland, UK

^u Département de Physique de la Matière Condensée, Université de Genève, Geneva, Switzerland

^v School of Physics, Trinity College, Dublin, D2 Dublin, Ireland

^w Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College, Dublin, D2 Dublin, Ireland

^x School of Chemistry, Trinity College, Dublin, D2 Dublin, Ireland

^y Texas Instruments Incorporated, Dallas, TX, USA

^z Unité Mixte de Physique CNRS/Thales, Palaiseau, France

^aa Université de Paris-Sud, Orsay, France

^ab Instituto de Ciencia de Materiales de Madrid, CSIC, Madrid, Spain

^ac Leiden University, Faculty of Science, Leiden Institute of Chemistry, Leiden 2333 CC, The Netherlands

^ad Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands

^ae Institute of Chemical Engineering Sciences (ICE-HT/FORTH), Rio, Greece

^af Department of Chemical Engineering, University of Patras, Rio, Greece

^ag Electrical Engineering Institute, Ecole Polytechique Fédérale de Lausanne, Lausanne, Switzerland

^ah Institute for Molecules and Materials, Radboud University Nijmegen, Nijmegen, The Netherlands

^ai Laboratoire d'Etude des Microstructures (LEM), ONERA-CNRS, Chatillon, France

^aj CNR-Istituto per la Microelettronica e i Microsistemi, Bologna, Italy

^ak Advanced Microelectronic Centre Aachen, AMO GmbH, Aachen, Germany

^al NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, Pisa, Italy

^am Airbus UK Ltd, Broughton, UK

^an Department of Chemistry, Seoul National University, Seoul, South Korea

^ao School of Electrical & Electronic Engineering, Yonsei University, Seoul, South Korea

^ap Department of Engineering Science, University of Oxford, Oxford, UK

^aq Department of Microtechnology and Nanoscience, Chalmers University of Technology, Gothenburg, Sweden

^ar Physics of Nanodevices, Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands

^as STMicroelectronics, Arzano (Naples), Italy

^at Materials Science Centre, School of Materials, University of Manchester, Manchester, UK

^au Institut für Physik, Technische Universität Chemnitz, Chemnitz, Germany

^av Institut LITEN, CEA LITEN, Grenoble Cedex 9, France

^aw Max-Planck-Institut für Polymerforschung, Mainz, Germany

^ax Aixtron Ltd., Cambridge, UK

^ay Aalto University, Finland

^az CambridgeIP, Cambridge, UK

^ba Department of Applied Physics, Chalmers University of Technology, Gothenburg, Sweden