1. Department of Physics, Chandigarh University, Mohali, Punjab, India
2. Department of Applied Sciences, MSIT, C-4, Janakpuri, New Delhi, India
3. Department of Applied Sciences, Chandigarh Engineering College, Mohali, Punjab, India
4. King Abdullah Institute for Nanotechnology, King Saud University, P. O. Box 2455, Riyadh 11451, Saudi Arabia