1Institute of Chemistry of Condensed Matter and Technologies for Energy, CNR ICMATE, Corso Stati Uniti 4, 35127, Padova, Italy
2Departmento de Fısica Aplicada, Universidad de Cantabria, Avda. Los Castros S/n, 39005 Santander, Spain
3Institute of Physics, University of Munster, Heisenbergstraße 11, 48149 Munster, Germany
4Departamento de Ciencias de La Tierra y Fısica de La Materia Condensada, Universidad de Cantabria, Cantabria Campus Internacional, Avda. de Los Castros S/n, 39005 Santander, Spain
5Institute of Nanotechnology, CNR-NANOTEC, Via Orabona 4, 70126 Bari, Italy
6Tyndall National Institute University College Cork, Lee Maltings, Dyke Parade, T12 R5CP Cork, Ireland
7Center for Surface and Nanoanalytics, Johannes Kepler University, 4040 Linz, Austria
8TE-OX, 21 Rue Jean Rostand, 91400 Orsay, France
9VLC Photonics S.L. Universidad Politecnica de Valencia (access I), Camino de Vera S/n, 46022 Valencia, Spain
10NANOM MEMS Srl, G. Cosbuc 9, 505400 Rasnov, Brasov, Romania
11Heidelberg University, Kirchhoff-Institute for Physics, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
∗Corresponding author maria.losurdo@cnr.it