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