1. National Key Laboratory of Science and Technology on Micro/Nano Fabrication Laboratory Department of Micro/Nano Electronics University of Michigan‐Shanghai Jiao Tong University Joint Institute Shanghai Jiao Tong University Shanghai 200240 China
2. Key Laboratory of Polar Materials and Devices Ministry of Education East China Normal University Shanghai 200241 China
3. Herbert Gleiter Institute of Nanoscience Nanjing University of Science and Technology Nanjing 210094 China