1. Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology (KAIST) Daejeon 34141 Republic of Korea
2. Department of Mechanical and Aerospace Engineering The Hong Kong University of Science and Technology Kowloon Hong Kong 999077 P. R. China
3. Department of Building and Real Estate The Hong Kong Polytechnic University Hung Hom Kowloon Hong Kong 999077 P. R. China
4. Max Planck Institute for Chemical Physics of Solids 01187 Dresden Germany
5. National Synchrotron Radiation Research Center Hsinchu 30076 Taiwan
6. Department of Chemical and Biological Engineering The Hong Kong University of Science and Technology Kowloon Hong Kong P. R. China