1. Department of Materials Science
2. State Key Laboratory of ASIC and Systems
3. Fudan University
4. Shanghai 200433
5. People's Republic of China
6. Center of Nanoelectronics and School of Microelectronics
7. Shandong University
8. Jinan 250100
9. P. R. China
10. Department of Physics
11. State Key Laboratory of Functional Materials for Informatics
12. Shanghai Institute of Microsystem and Information Technology
13. Chinese Academy of Sciences
14. Shanghai 200050