1. Information Materials and Intelligent Sensing Laboratory of Anhui Province, Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, P. R. China
2. Nanchang Institute of Technology, Nanchang 330044, P. R. China
3. Key Laboratory of Materials Physics, Anhui Key Laboratory of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China
4. University of Science and Technology of China, Hefei 230026, P. R. China
5. Hefei Innovation Research Institute, School of Microelectronics, Beihang University, Hefei 230013, P. R. China