1. Department of Physics, Sathyabama Institute of Science and Technology, Chennai-600119, India
2. Centre for Nanoscience and Nanotechnology, Sathyabama Institute of Science and Technology, Chennai-600119, India
3. Graduate School of Science and Technology, Tokai University, Kanagawa 259-1292, Japan
4. Department of Physics, Tokai University, Kanagawa 259-1292, Japan
5. Micro/Nano Technology Centre, Tokai University, Kanagawa 259-1292, Japan