1. College of Materials Science and Opto-Electronic Technology
2. Key Laboratory of Vacuum Physic
3. University of Chinese Academy of Sciences
4. Beijing 100049
5. P. R. China
6. School of Electronic, Electrical and Communication Engineering
7. College of Chemistry
8. Ministry of Education
9. Beijing Normal University
10. Beijing 100875
11. Department of Physics and Astronomy
12. Shanghai Jiaotong University