1. Department of Materials Science, State Key Laboratory of ASIC and Systems, Fudan University, Shanghai 200433, P. R. China.
2. Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, P. R. China.
3. Center for Bio-Integrated Electronics, Northwestern University, Evanston, IL 60208, USA.
4. Department of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, South Korea.
5. Department of Physics, Fudan University, Shanghai 200433, P. R. China.