1. Department of Physics, University College of Engineering, Bharathidasan Institute of Technology Campus, Anna University, Tiruchirappalli, Tamil Nadu 620 024, India
2. Graphene & Advanced 2D Materials Research Group (GAMRG), School of Engineering and Technology, Sunway University, 5 Jalan Universiti, Bandar Sunway, 47500 Petaling Jaya, Selangor, Malaysia