1. Department of Materials Science and Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong 999077, China
2. Key Laboratory of Material Physics, Ministry of Education, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450001, China
3. Hong Kong Institute for Advanced Study, City University of Hong Kong, Kowloon, Hong Kong, 999077, China
4. Hong Kong Institute for Clean Energy, City University of Hong Kong, Kowloon 999077, Hong Kong
5. Centre for Functional Photonics, City University of Hong Kong, Kowloon, Hong Kong