Affiliation: | a Department of Physics, Udai Pratap Autonomous College, Varanasi-221002, Indiab Department of Applied Physics, Institute of Technology, Banaras Hindu University, Varanasi-221005, Indiac Department of Physics, National Institute of Singapore, 2 Science Drive 2, S117542, Singapored Department of Ceramic Engineering, Institute of Technology, Banaras Hindu University, Varanasi-221005, India |