1. Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583, Singapore
2. Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
3. Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, Singapore 117603, Singapore
4. Université Polytechnique Hauts de France, Institut d’Electronique, de Microélectronique et de Nanotechnologie─Site de Valenciennes, IEMN CNRS UMR 8520, Valenciennes 59309, France