1. Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong Special Administrative Region (SAR) 999077, China.
2. Centre for Advanced Structural Materials, City University of Hong Kong, Hong Kong SAR 999077, China.
3. IBM T. J. Watson Research Center, Yorktown Heights, NY 10598, USA.
4. Centre of Super-Diamond and Advanced Films, City University of Hong Kong, Hong Kong SAR 999077, China.
5. State Key Laboratory of Physical Chemistry of Solid Surfaces, Department of Chemistry, Xiamen University, Xiamen 361005, China.
6. Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR 999077, China.
7. Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA.
8. Department of Nuclear Science and Engineering and Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
9. Shenzhen Research Institute, City University of Hong Kong, Shenzhen 518057, China.