1. State Key Laboratory of Modern Optical Instrumentation,
Zhejiang University, Hangzhou 310027, People's Republic of China
2. Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, People's Republic of China
3. Department of Materials, Faculty of Engineering, University of Ulm, Albert-Einstein Allee 47, D-89081 Ulm,
Germany
4. International Center for New-Structured Materials, State Key Laboratory of
Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China