1. Functional Nanomaterials Research Laboratory (FNRL), Department of Physics and Centre for Nanotechnology, Indian Institute of Technology Roorkee, Roorkee-247667, Uttarakhand, India
2. Nanoelectronics Centre, Advanced Technology Institute, University of Surrey, Guildford, Surrey GU27XH, United Kingdom
3. Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India