1. Institute for Microelectronics and Microsystems, National Research Council, Via P. Castellino 111, 80131 Naples, Italy
2. Department of Physics “E. Pancini,” University of Naples “Federico II,” Via Cinthia, 80126 Naples, Italy
3. Université de Tours, GREMAN UMR 7347, INSA-CVL, CNRS, 16 Rue Pierre et Marie Curie, 37071 Tours Cedex 2, France
4. Department of Chemical Sciences, University of Naples “Federico II,” Via Cinthia, 80126 Naples, Italy