1. Department of Materials Science & Technology, University of Crete, P.O. Box 2208, 71003 Heraklion, Greece
2. Microelectronics Research Group, IESL-FORTH, P.O. Box 1385, 71110 Heraklion, Greece
3. Department of Electrical & Computer Engineering, Hellenic Mediterranean University, 71410 Heraklion, Greece
4. Institute of Electronic Structure & Laser, FORTH, P.O. Box 1385, 71110 Heraklion, Greece