1. School of Materials Science and Engineering, Nanyang Technological University, Singapore639798
2. Department of Physics, Prabhat Kumar College, Contai, West Bengal 721401, India
3. Interdisciplinary Graduate School, Nanyang Technological University, Singapore637371
4. Energy Research Institute @ NTU (ERI@N), Nanyang Technological University, Singapore 637553
5. Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Singapore 138634
6. Campus for Research Excellence And Technological Enterprise (CREATE), Singapore 138602