1. School of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, P. R. China
2. Key Laboratory of Microelectronics and Energy of Henan Province, Xinyang Normal University, Xinyang 464000, P. R. China
3. College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471934, P. R. China
4. Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P. R. China