[1] CEA, Liten, F-38054 Grenoble 9, France
[2] Technol Educ Inst TEI Crete, Ctr Mat Technol & Photon, Iraklion 71004, Crete, Greece
[3] Technol Educ Inst TEI Crete, Dept Elect Engn, Iraklion 71004, Greece
[4] Univ Oxford, Dept Mat, Oxford OX1 3PH, England
[5] Ist Italiano Tecnol, Graphene Labs, I-16163 Genoa, Italy
[6] Ist Italiano Tecnol, Nanochem Dept, I-16163 Genoa, Italy
[7] Sabanci Univ, Fac Engn & Nat Sci, TR-34956 Istanbul, Turkey
[8] Ataturk Univ, Dept Chem Engn, TR-25240 Erzurum, Turkey
[9] Univ Padua, Dept Chem Sci, Padua, Italy
[10] Umea Univ, Dept Phys, SE-90187 Umea, Sweden
[11] Tech Univ Dresden, Theoret Chem, D-01062 Dresden, Germany
[12] Fdn Bruno Kessler, REET Unit, I-38123 Trento, Italy
[13] NEST Scuola Normale Super, Ist Nanosci Cnr, I-56127 Pisa, Italy
[14] Thales Res & Technol, F-91767 Palaiseau, France
[15] CIC EnergiGUNE, Minano 01510, Alava, Spain
[16] Basque Fdn Sci, IKERBASQUE, Bilbao, Spain
[17] Univ Cambridge, Dept Cambridge, Cambridge CB2 1EW, England
[18] Univ Cambridge, Cambridge Graphene Ctr, Cambridge CB3 0FA, England