1. Department of Electrical and Electronics Engineering, Nanotechnology Research Center (NANOTAM), Bilkent University, Ankara, Turkey
2. Nanotechnology Research Center (NANOTAM), Bilkent University, Ankara, Turkey
3. UNAM-Institute of Materials Science and Nanotechnology and the Department of Physics, Bilkent University, Ankara, Turkey
4. Department of Engineering Physics, Ankara University, Ankara, Turkey
5. Department of Electrical and Electronics Engineering, Institute of Materials Science and Nanotechnology (UNAM), and the Department of Physics, Nanotechnology Research Center (NANOTAM), Bilkent University, Ankara, Turkey