1. Center of Materials Technology and Photonics and Electrical Engineering Department Technological Educational Institute (TEI) of Crete Heraklion 71004 Crete Greece
2. Department of Materials Science and Technology University of Crete Heraklion 710 03 Crete Greece
3. Institute of Electronic Structure and Laser Foundation for Research and Technology – Hellas P. O. Box 1527 Heraklion 711 10 Crete Greece
4. Consiglio Nazionale delle Ricerche Istituto di Struttura della Materia Area di Ricerca di Tor Vergata Via del Fosso del Cavaliere, 100 00133 Roma Italy
5. Istituto Italiano di Tecnologia Graphene Labs Via Morego 30‐16163 Genoa Italy