1 CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Center for Nanoscience and Technology, Beijing 100190, P. R. China. xielm@nanoctr.cn.
2 Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan, Republic of China. ysh@mail.ntust.edu.tw.
3 State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
4 CAS Key Laboratory of Standardization and Measurement for Nanotechnology, National Center for Nanoscience and Technology, Beijing 100190, P. R. China. xielm@nanoctr.cn and Center for Nanochemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
5 Center for Nanochemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.