1. Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066, India
2. Department of Chemical, Biological and Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Salt Lake, Kolkata 700 098, India
3. Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
4. Centre for Advanced 2D Materials (CA2DM) and Department of Chemistry, National University of Singapore, 117546 Singapore