1. Department
of Physics, National University of Singapore, 2 Science Drive 3, 117542 Singapore
2. Singapore
Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 1176033
3. SZU-NUS
Collaborative Innovation Center for Optoelectronic Science and Technology,
Key Laboratory of Optoelectronic Devices and Systems of Ministry of
Education and Guangdong Province, Shenzhen University, Shenzhen 518060, China
4. Department
of Chemistry, National University of Singapore, 3 Science Drive 3, 117543 Singapore
5. NUSNNI-NanoCore, National University of Singapore, Singapore 117411