1. Hunan Institute of Advanced Sensing and Information Technology, Xiangtan University, Xiangtan, Hunan 411105, PR China
2. School of Physics and Optoelectronics, Xiangtan University, Xiangtan, Hunan 411105, PR China
3. School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, PR China
4. Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, Xiangtan University, Xiangtan, Hunan 411105, PR China
5. College of Physics and Electronics Engineering, Hengyang Normal University, Hengyang 421002, PR China