1. Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, I-20133 Milano, Italy
2. Institute of Condensed Matter and Nanoscience (IMCN), Université Catholique de Louvain, B-1348 Louvain-laneuve, Belgium
3. Institute of Materials Science (ICMUV), University of Valencia, Catedrático Beltrán 2, E-46980 Valencia, Spain
4. IFN-CNR, Piazza L. da Vinci 32, I-20133 Milano, Italy
5. Cambridge Graphene Centre, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, United Kingdom
6. Electrical Engineering Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland
7. Université du Luxembourg, 162 A, avenue de la Faencerie, Luxembourg City L-1511, Luxembourg
8. Division of Ultrafast Process in Materials (FLASHit), CNR-ISM, Area della Ricerca di Roma 1, 00016 Monterotondo Scalo, Italy