1. Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing 100190 China
2. University of Chinese Academy of Sciences Beijing 100190 China
3. State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Materials Xiamen University Simingnan Road 422 Xiamen 361005 China
4. Center of Materials Science and Optoelectronics Engineering University of the Chinese Academy of Sciences Beijing 100049 China