1 National Key Laboratory of Science and Technology on Micro/Nano Fabrication, Institute of Microelectronics, Peking University, Beijing 100871, China
2 Quantum Science and Engineering Centre, Nanyang Technological University, Singapore 639798, Singapore
3 Institute of Microelectronics, A*STAR (Agency for Science, Technology and Research), Singapore 138634, Singapore
4 School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore
5 e-mail: haoyl@pku.edu.cn
6 e-mail: yi_zhang@ntu.edu.sg
7 e-mail: eaqliu@ntu.edu.sg