1. Center on Nanoenergy Research, School of Physical Science and Technology, Guangxi University, Nanning 530004, China
2. Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 101400, China
3. School of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing 100049, China
4. School of Integrated Circuits and Electronics, Beijing Institute of Technology, Beijing 100081, China