1. Department of Electrical and Electronics Engineering, Birla Institute of Technology and Science Pilani, Pilani 333031, India
2. Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, United States
3. Physics Discipline, Indian Institute of Technology Gandhinagar, Gandhinagar 382424, India
4. Department of Electrical Engineering, University of Arkansas, Fayetteville, Arkansas 72701, United States