1. National Laboratory of Solid State Microstructure, School of Physics, Nanjing University, Nanjing, Jiangsu 210093, People’s Republic of China
2. Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, Jiangsu 210093, People’s Republic of China
3. Vacuum Interconnected Nanotech Workstation (Nano-X), Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences (CAS), Suzhou, Jiangsu 215123, People’s Republic of China