[1] Bilkent Univ, UNAM Natl Nanotechnol Res Ctr, TR-06800 Ankara, Turkey
[2] Bilkent Univ, Inst Mat Sci & Nanotechnol, TR-06800 Ankara, Turkey
[3] Fatih Univ, Bionanotechnol R&D Ctr, TR-34500 Istanbul, Turkey
[4] Yildiz Tech Univ, Phys Dept, TR-34220 Istanbul, Turkey
[5] Arel Univ, Elect & Elect Engn, TR-34295 Istanbul, Turkey
[6] Acarkent Doga IB World Sch, Acarkent Site,3rd St,25, TR-34800 Istanbul, Turkey
[7] Queen Mary Univ London, Ctr Condensed Matter & Mat Phys, Sch Phys & Astron, London E1 4NS, England