1. Center of Super-Diamond and Advanced Films (COSDAF), Department of Physics and Materials Science, City University of Hong Kong, Hong Kong; City University of Hong Kong Shenzhen Research Institute, Shenzhen 518057, People's Republic of China
2. School of Chemical and Materials Engineering, National University of Sciences and Technology, Sector H-12, Islamabad 44000, Pakistan
3. School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009, People's Republic of China