1. Department of Applied Physics, The Hong Kong Polytechnic University, Hung
Hom, Kowloon, People’s Republic of China
2. The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen, People’s Republic of China
3. CAS Key Laboratory of Standardization and
Measurement for Nanotechnology, National Center for Nanoscience and
Technology, Beijing, People’s Republic of China