1. School of Electronic Science and Engineering, Xiamen University, Xiamen 361005, P. R. China
2. Shenzhen Research Institute of Xiamen University, Shenzhen 518000, P. R. China
3. College of Energy, Xiamen University, Xiamen 361102, P. R. China
4. College of Physics & Information Engineering, Quanzhou Normal University, Quanzhou 362000, P. R. China
5. State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China