1. Department of Materials Science and Engineering City University of Hong Kong 83 Tat Chee Avenue Kowloon Hong Kong 999077 P. R. China
2. Department of Applied Physics and Research Institute for Smart Energy The Hong Kong Polytechnic University Hung Hom Kowloon Hong Kong P. R. China
3. Center for Advanced Nuclear Safety and Sustainable Development City University of Hong Kong Kowloon Hong Kong P. R. China