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