1. Department of Physics, Hong Kong University of Science and Technology, Clear Water
Bay, Kowloon 999077, Hong Kong, China
2. Department of Chemistry, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou 310018, China
3. Department of Materials Science & Engineering, Northwestern University, Evanston, Illinois 60208-3120, United States
4. Materials Characterization and Preparation Facility (GZ), Advanced Materials Thrust, The Hong Kong University of Science and Technology (Guangzhou), Guangzhou 511400, Guangdong, China
5. Department of Chemical and Biological Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong, China
6. William Mong Institute of Nano Science and Technology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong, China