1. Key Laboratory of Materials Physics; CAS Center for Excellence in Nanoscience, and Anhui Key Laboratory of Nanomaterials and Nanotechnology, Institute of Solid State Physics; Chinese Academy of Sciences; Hefei Anhui 230031 China
2. University of Science and Technology of China; Hefei Anhui 230026 China
3. Institute of Technical Biology and Agriculture Engineering, Hefei Institutes of Physical Science; Chinese Academy of Sciences; Hefei 230031 China