1. State Key Laboratory on Integrated Optoelectronics; Institute of Semiconductors, Chinese Academy of Science; PO BOX 912, Beijing 100083 China
2. Center for Physicochemical Analysis and Measurement; Institute of Chemistry, Chinese Academy of Sciences; Beijing 100190 China
3. Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences; Suzhou 215123 China
4. State Key Laboratory on Integrated Optoelectronics; College of Electronic Science and Engineering, Jilin University; Changchun 130023 China