1. Department of Materials Science and Engineering; City University of Hong Kong; Hong Kong SAR P. R. China
2. City University of Hong Kong Shenzhen Research Institute; Shenzhen P. R. China
3. Center of Super-Diamond and Advanced Films (COSDAF) & Department of Chemistry; City University of Hong Kong; Hong Kong SAR P. R. China
4. Department of Materials Science and Engineering; North Carolina State University; Raleigh NC 27695 United States