1. Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Republic of Singapore
2. Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, 117575 Singapore
3. Science, Mathematics and Technology, Singapore University of Technology and Design, 8 Somapah Road, 487372 Singapore
4. Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 Singapore
5. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore