1. Key
Laboratory of Optoelectronics Information Technology (Tianjin University),
Ministry of Education, School of Precision Instruments and Optoelectronics
Engineering, Tianjin University, Tianjin 300072, China
2. Tianjin
Key Laboratory of Low Dimensional Materials Physics and Preparing
Technology, School of Science, Tianjin University Tianjin, 300072, China
3. Center
of Material Science, National University of Defense Technology Changsha 410073, China