1 CAS Center for Excellence in Nanoscience, Beijing Key Laboratory of Micro-nano Energy and Sensor, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 101400, China; School of Nanoscience and Engineering, University of Chinese Academy of Sciences, Beijing 100049, China; School of Electrical & Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore.
2 State Key Laboratory of Tribology in Advanced Equipment, Tsinghua University, Beijing 100084, China; Institute of New Materials and Advanced Manufacturing, Beijing Academy of Science and Technology, Beijing 100084, China.
3 CAS Center for Excellence in Nanoscience, Beijing Key Laboratory of Micro-nano Energy and Sensor, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 101400, China; Center on Nanoenergy Research, School of Physical Science and Technology, Guangxi University, Nanning 530004, China.
4 CAS Center for Excellence in Nanoscience, Beijing Key Laboratory of Micro-nano Energy and Sensor, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 101400, China; Institute of Intelligent Flexible Mechatronics, Jiangsu University, Zhenjiang 212013, China.
5 CAS Center for Excellence in Nanoscience, Beijing Key Laboratory of Micro-nano Energy and Sensor, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 101400, China; School of Nanoscience and Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
6 State Key Laboratory of Tribology in Advanced Equipment, Tsinghua University, Beijing 100084, China.
7 State Key Laboratory of Tribology in Advanced Equipment, Tsinghua University, Beijing 100084, China. Electronic address: xgx2014@tsinghua.edu.cn.
8 CAS Center for Excellence in Nanoscience, Beijing Key Laboratory of Micro-nano Energy and Sensor, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 101400, China; School of Nanoscience and Engineering, University of Chinese Academy of Sciences, Beijing 100049, China; Center on Nanoenergy Research, School of Physical Science and Technology, Guangxi University, Nanning 530004, China. Electronic address: czhang@binn.cas.cn.