1. Istituto Italiano di Tecnologia, Graphene Labs, Via Morego 30, I-16163 Genova, Italy.
2. School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK.
3. Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany.
4. Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany.
5. University of Sheffield, Sheffield S3 7RH, UK.
6. Centro S3, Istituto Nanoscienze-CNR, via Campi 213/a 41125 Modena, Italy.
7. Center for Nanotechnology Innovation at NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy.
8. Fakultät für Physik, Universität Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany.
9. ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona 08860, Spain.
10. ICREA - Institució Catalana de Reçerca i Estudis Avancats, 08010 Barcelona, Spain.