1 Center for Excellence in Nanoscience (CAS), Key Laboratory of Nanosystem and Hierarchical Fabrication (CAS), National Center for Nanoscience and Technology, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049, China.
2 Center for Excellence in Nanoscience (CAS), Key Laboratory of Nanosystem and Hierarchical Fabrication (CAS), National Center for Nanoscience and Technology, Beijing 100190, China.
3 Center for Excellence in Nanoscience (CAS), Key Laboratory of Nanosystem and Hierarchical Fabrication (CAS), National Center for Nanoscience and Technology, Beijing 100190, China. Electronic address: xiaoz@nanoctr.cn.
4 Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, China. Electronic address: sfyang@ustc.edu.cn.
5 School of Physics & Electronics, Central South University, Changsha 410083, China. Electronic address: yuanyb@csu.edu.cn.
6 Center for Excellence in Nanoscience (CAS), Key Laboratory of Nanosystem and Hierarchical Fabrication (CAS), National Center for Nanoscience and Technology, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: ding@nanoctr.cn.