1. Institute of Nanotechnology─Nanotec Consiglio Nazionale delle Ricerche─Sede di Cosenza. Ponte P. Bucci - Cubo 33C, Rende 87036, Italy
2. Physics Department, University of Calabria, 87036 Arcavacata di Rende, CS, Italy
3. Departamento de Ciencia de los Materiales, I. M. y Q. I., IMEYMAT, Facultad de Ciencias, Universidad de Cádiz, Campus Río San Pedro, s/n, 11510 Puerto Real, Cádiz, Spain
4. Department of Mechanical, Energy and Management Engineering, University of Calabria, Cubo 44C, Arcavacata di Rende 87036, Italy
5. Institute for Microelectronics and Microsystems─IMM Consiglio Nazionale delle Ricerche, via del Fosso del Cavaliere 100, 00133 Roma, Italy