1. Department of Physics, National University of Singapore, 117542 Singapore
2. NUSNNI-NanoCore, National University of Singapore, 117411 Singapore
3. Department of Materials Science and Engineering, National University of Singapore, 117575 Singapore
4. Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, 117603 Singapore
5. National University of Singapore Graduate School for Integrative Sciences and Engineering (NGS), 28 Medical Drive, 117456 Singapore
6. Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore