1. Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education and Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices
2. School of Physics and Electronics
3. Hunan University
4. Changsha 410082
5. China
6. Institute for Optoelectronics
7. Department of Materials Science
8. Fudan University
9. Shanghai 200433