1. Department of Physics, National University of Singapore, Singapore 117551, Singapore
2. Centre for BioImaging Sciences, Department of Biological Sciences, National University of Singapore, Singapore 117557, Singapore
3. Department of Chemistry, National University of Singapore, Singapore 117543, Singapore
4. imec, Kapeldreef 75, Leuven B-3001, Belgium
5. Department of Materials & Chemistry, Vrije Universiteit Brussel, Brussel B-1050, Belgium
6. Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546, Singapore
7. Hybrid Materials for Opto-Electronics Group, Department of Molecules and Materials, MESA+ Institute for Nanotechnology and Center for Brain-Inspired Nano Systems, Faculty of Science and Technology, University of Twente, 7500 AE Enschede, The Netherlands
8. Department of Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore