1. Department of Materials Science and Engineering, National University of Singapore, Singapore 117575
2. Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, Singapore 117603
3. Data Storage Institute, A*STAR, 2 Fusionopolis Way, #08-01 Innovis, Singapore 138634
4. NUSNNI-Nanocore, National University of Singapore, Singapore 117411
5. Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576
6. Department of Physics, National University of Singapore, Singapore 117542
7. Department of Integrative Science and Engineering, National University of Singapore, Singapore 117542