1. Department of Materials Science and Engineering, and Center for Functional Photonics (CFP), City University of Hong Kong, 83 Tat Chee Avenue, Kowloon 999077, Hong Kong SAR, China
2. Department of Electrical and Electronic Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon 999077, Hong Kong SAR, China
3. Hong Kong Branch of National Precious Metals Material Engineering Research Centre, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon 999077, Hong Kong SAR, China