1. Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education, Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics & Devices School of Physics and Electronics, Hunan University, Changsha 410082, People’s Republic of China
2. College of Electrical and Information Engineering, Hunan University of Technology, Zhuzhou 412007, People’s Republic of China
3. State Key Laboratory of Chemo/Biosensing and Chemometrics, Provincial Hunan Key Laboratory for Graphene Materials and Devices, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, People’s Republic of China
4. Department of Materials Science & Engineering, University of Washington, Seattle, Washington 98195, United States