1. Department of Applied Physics The Hong Kong Polytechnic University Kowloon 999077 Hong Kong
2. China & Polytechnic University of Hong Kong Shenzhen Research Institute Shenzhen 518000 China
3. Beijing Key Laboratory of Optoelectronic Functional Materials & Micro‐nano Devices Department of Physics Renmin University of China Beijing 100872 China
4. Department of Chemistry and Center of Super‐Diamond & Advanced Films (COSDAF) City University of Hong Kong Kowloon 999077 Hong Kong
5. China & City University of Hong Kong Shenzhen Research Institute Shenzhen 518000 China
6. Department of Physics Hong Kong University of Science and Technology Clear water bay Hong Kong 999077 China