1. International Joint Research Laboratory of New Energy Materials and Devices of Henan Province, School of Physics and Electronics, Henan University, Kaifeng, 475004, PR China
2. College of Electronics and Engineering, North China University of Water Resources and Electric Power, Zhengzhou 450046, PR China
3. National Demonstration Center for Experimental Physics and Electronics Education, School of Physics and Electronics, Henan University, Kaifeng, 475004, PR China