1. Center of Super-Diamond and Advanced Films (COSDAF) and Department
of Physics and Materials Science, City University of Hong Kong, Hong Kong, Hong Kong SAR
2. Department of Chemistry, South University of Science and Technology of China, Shen Zhen, Guangdong 518000, P. R. China
3. The Key Laboratory of Space Applied Physics and Chemistry, Ministry
of Education and Shaanxi Key Laboratory of Macromolecular Science
and Technology, School of Science, Northwestern Polytechnical University, Xi’an, Shaanxi 710072, P. R. China