1. Physics Division, Department of Mathematical Sciences, Xi’an Jiaotong-Liverpool University, Suzhou 215123, China
2. Key Laboratory of Terahertz Solid-State Technology, CAS, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050, China
3. Institute of Microelectronics, Tsinghua University, Beijing 100084, China
4. Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
5. State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
6. Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Gothenburg, Sweden
7. Department of Physics, The University of Hong Kong, Pokfulam, Hong Kong, China