1. Materials Research Laboratory, Department of Physics, Banaras Hindu University, Varanasi 221005, India
2. Department of Physics, NSIT, New Delhi 110078, India
3. Department of Physics, ARSD College, University of Delhi, New Delhi 110021, India
4. National Sun Yat-Sen University, Kaohsiung, Taiwan
5. AMPRI, CSIR, Bhopal 462026, India