1. Department of Chemistry and Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Kowloon, Hong Kong 999077, China
2. City University of Hong Kong Shenzhen Research Institute, Shenzhen 518057, China
3. Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon, Hong
Kong 999077, China
4. Polytechnic University of Hong Kong Shenzhen Research Institute, Shenzhen 518057, China
5. Physics Department and Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, Huaiyin Normal University, Huaian 223300, China