1. Department of Physics, Cochin University of Science and Technology, Kerala 682022, India
2. Department of Physics, Government Arts College, Thiruvananthapuram, Kerala 695014, India
3. Centre of Excellence in Advanced Materials, Cochin University of Science and Technology, Kerala 682022, India
4. Inter University Centre for Nanomaterials and Devices, Cochin University of Science and Technology, Kerala 682022 India