1. Centre for Advanced Optoelectronic Functional Materials Research
and Key Laboratory of UV-Emitting Materials and Technology (Northeast Normal University), Ministry of Education, Changchun 130024, China
2. Division of Nanophotonics, CAS Key Laboratory of Standardization
and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China
3. National Demonstration Center for Experimental
Physics Education, Northeast Normal University, Changchun 130024, China
4. Department of Materials Science and Engineering,
College of Engineering, Peking University, Beijing 100871, China
5. Center for Programmable Materials, School
of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore