1. Division
of Physics and Applied Physics, School of Physical and Mathematical
Sciences, Nanyang Technological University, Singapore 637371, Singapore
2. NOVITAS,
Nanoelectronics Centre of Excellence, School of Electrical and Electronic
Engineering, Nanyang Technological University, Singapore 639798, Singapore
3. State
Key Laboratory of Luminescence and Applications, Changchun Institute
of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, P. R. China
4. Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
5. School
of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
6. Materials Science
and
Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
7. School
of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
8. Centre
for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637371, Singapore