1. IMM-CNR Institute for Microelectronic and Microsystems, Campus Ecotekne, Via Monteroni, 73100 Lecce, Italy
2. CNR-Nanotec, Nanotechnology Institute, Campus Ecotekne, Via Monteroni, 73100 Lecce, Italy
3. Mathematics and Physics Department, University of Salento, Via Monteroni, 73100 Lecce, Italy
4. King Abdulaziz City for Science and Technology, National Nanotechnology Research Centre, 11541 Riyadh, Kingdom of Saudi Arabia