1. Department
of Physics, Politecnico di Milano, P.zza L. Da Vinci 32, 20133 Milano, Italy
2. Laboratory of Bio-inspired & Graphene Nanomechanics, Department of Civil, Environmental and Mechanical Engineering, Università di Trento, via Mesiano 77, 38123 Trento, Italy
3. Laboratoire
de Photonique et de Nanostructures, CNRS, Université Paris-Saclay, route de Nozay, F-91460 Marcoussis, France
4. Center for Materials
and Microsystems, Fondazione Bruno Kessler, Via Sommarive 18, 38123 Povo (TN), Italy
5. School
of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
6. IFN-CNR, P.zza L. Da Vinci 32, 20133 Milano, Italy