1. Department of Materials Science and Engineering, National University of Singapore, Singapore 117575
2. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
3. NUSNNI-NanoCore, National University of Singapore, Singapore 117411
4. Imaging and Characterization Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
5. Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603
6. School of Materials Science and Engineering, University of New South Wales (UNSW), Sydney, NSW 2052, Australia