1. Department of Applied Physics, Photonic Research Institute, Materials Research Center, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
2. Shenzhen Research Institute, The Hong Kong Polytechnic University, 518057 Shenzhen, Guangdong, People's Republic of China
3. Department of Applied Biology and Chemical Technology, Research Institute for Smart Energy, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong