1. Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Department of Physics, Renmin University of China, Beijing 100872, People’s Republic of China
2. School of Aerospace Engineering, Beijing Institute of Technology, Beijing 100081, People’s Republic of China
3. College of Electronic and Optical Engineering & College of Microelectronics, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
4. CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Centre for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing 100190, People’s Republic of China
5. Department of Applied Physics, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan