1. State Key Laboratory of Silicon Materials; School of Materials Science and Engineering; Cyrus Tang Center for Sensor Materials and Application; Zhejiang University; Hangzhou 310027 China
2. Center of Electron Microscope; School of Materials Science and Engineering; Zhejiang University; Hangzhou 310027 China
3. School of Materials Science and Engineering; Nanyang Technological University; Block N4.1, 50 Nanyang Avenue Singapore 639798 Singapore
4. Department of Physics; Zhejiang University; Hangzhou 310027 China
5. Department of Physics; Chinese University of Hong Kong; Hong Kong 999077 China
6. EMAT; University of Antwerp; B-2020 Antwerp Belgium
7. Nanostructure Research Center; Wuhan University of Technology; 430074 Wuhan China