1. School of Materials Science and Engineering
2. Zhejiang University
3. Hangzhou 310027
4. P. R. China
5. Department of Materials and Environmental Chemistry
6. Arrhenius Laboratory
7. Stockholm University
8. S-106 91 Stockholm
9. Sweden
10. Science and Technology on Surface Physics and Chemistry Laboratory
11. Mianyang 621907
12. Center of Electron Microscopy