1. MESA+ Institute for Nanotechnology, University of Twente, Enschede, Netherlands.
2. NUSNNI-Nanocore, National University of Singapore, Singapore.
3. NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore.
4. Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA.
5. Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA, USA.
6. Department of Physics, National University of Singapore, Singapore.
7. Department of Electrical and Computer Engineering and Department of Materials Science and Engineering, National University of Singapore, Singapore.
8. School of Physics and Centre for Research on Adaptive Nanostructures and Nanodevices, Trinity College, Dublin, Ireland.