1. Advanced Materials Metrology and Life Science Division, Istituto Nazionale di Ricerca Metrologica INRIM, 10135 Torino, Italy
2. Institute of Physics, P.J. Šafárik University, 04154 Košice, Slovakia
3. Laboratory of Inorganic Materials, CERTH, 57001 Thermi-Thessaloniki, Greece
4. Department of Energy, Politecnico di Torino, 10129 Torino, Italy