1. Electrical and Computer Engineering, Democritus University of Thrace, 37791 Xanthi, Xanthi, Greece, 67100 (e-mail: nikvasil@ee.duth.gr)
2. Institute of Nanoscience and Nanotechnology, NCSR Demokritos, 54572 Agia Paraskevi, Attica, Greece, (e-mail: p.karakolis@inn.demokritos.gr)
3. Institute of Nanoscience and Nanotechnology, NCSR Demokritos, 54572 Agia Paraskevi, Attica, Greece, (e-mail: p.mandilas@inn.demokritos.gr)
4. Institute of Nanoscience and Nanotechnology, NCSR Demokritos, 54572 Agia Paraskevi, Attica, Greece, (e-mail: v.ioannou@inn.demokritos.gr)
5. Institute of Nanoscience and Nanotechnology, NCSR Demokritos, 54572 Agia Paraskevi, Attica, Greece, (e-mail: p.normand@inn.demokritos.gr)
6. IMM-CNR, STMicroelectronics Branch of Agrate Brianza, 68232 Agrate Brianza, Lombardy, Italy, (e-mail: michele.perego@mdm.imm.cnr.it)
7. School of Physics, Aristotle University of Thessaloniki, 37782 Thessaloniki, Central Macedonia, Greece, (e-mail: komnhnoy@auth.gr)
8. Electrical and Computer Engineering, Democritus University of Thrace, Xanthi, Eastern Macedonia and Thrace, Greece, 67100 (e-mail: vntinas@ee.duth.gr)
9. Electrical and Computer Engineering, Democritus University of Thrace, 37791 Xanthi, Xanthi, Greece, 67100 (e-mail: ifyrigos@ee.duth.gr)
10. Computer & Electrical Engineering, Democritus University of Thrace, XANTHI, Xanthi, Greece, 67100 (e-mail: ykar@ee.duth.gr)
11. Electrical and Computer Engineering, Democritus University of Thrace, Xanthi, Thrace, Greece, GR67100 (e-mail: gsirak@ee.duth.gr)
12. Institute of Nanoscience and Nanotechnology, National Center for Scientific Research Demokritos, Aghia Paraskevi, Attica, Greece, 15310 (e-mail: p.dimitrakis@inn.demokritos.gr)