1. State
Key Laboratory of Silicon Materials, School of Materials Science and
Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, P. R. China
2. CAS
Key Laboratory of Standardization and Measurement for Nanotechnology,
CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P. R. China
3. Key
Laboratory of Artificial Micro- and Nano-structures of Ministry of
Education, School of Physics and Technology, Wuhan University, Wuhan 430072, P. R. China