1. Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas (FORTH-IESL), GR-70013 Heraklion, Crete, Greece
2. Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi (CNR-IMM), Roma 00133, Italy
3. Department of Materials Science and Technology, University of Crete, GR-70013 Heraklion, Crete, Greece
4. School of Electrical and Computer Engineering, Aristotle University of Thessaloniki (AUTH), GR-54124 Thessaloniki, Greece