1. CNR‐SPIN Salerno via Giovanni Paolo II n. 132 Fisciano 84084 Italy
2. Department of Physical and Chemical Science University of L'Aquila via Vetoio, Coppito L'Aquila 67100 Italy
3. Physics Department “E. R. Caianiello” University of Salerno and CNR‐SPIN Salerno via Giovanni Paolo II n. 132 Fisciano 84084 Italy
4. Department of Electronic Engineering Faculty of Applied Energy System Jeju National University Jeju Special Self‐Governing Province Jeju‐si 63243 Korea
5. CNR‐SPIN L'Aquila via Vetoio, Coppito L'Aquila 67100 Italy