1. School of Physical Science and Technology, Inner Mongolia University, Hohhot, 010021, People's Republic of China
2. Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, 215123, People's Republic of China
3. Department of Physics & Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou, 510640, People's Republic of China
4. School of Materials Science and Engineering, Yancheng Institute of Technology, Yancheng, 224051, P. R. China
5. Coll Optoelect Sci & Engn, National University of Defense Technology, Changsha, 410073, People's Republic of China
6. State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing, 100871, People's Republic of China
7. Materials Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Mail Stop 66, Berkeley, California, 94720, USA