1. Department of Nanotechnology, Acharya Nagarjuna University, Nagarjunanagar - 522510, Guntur, India
2. Department of Physics, Rayalaseema University, Kurnool, India
3. Department of Physics, KL University, Vijayawada, India
4. Department of Physics, NRI Institute of Technology, Agiripalli, Krishna(Dt.), India