1. School of Materials Science and Engineering, The Key Laboratory of Advanced Materials of Ministry of Education, State Key Laboratory of New Ceramics and Fine Processing, Center for Flexible Electronics Technology, Tsinghua University, Beijing100084, China
2. Department of Physics, Tsinghua University, Beijing100084, China
3. Department of Electronic Engineering, Beijing National Research Center for Information Science and Technology, Center for Flexible Electronics Technology, IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing100084, China