1. Key Laboratory of Microelectronic and Energy of Henan ProvinceSchool of Physics and Electronic EngineeringXinyang Normal University Xinyang 464000, P. R. China
2. Institute of Inspection TechnologyXinyang Vocational and Technical College Xinyang 464000, P. R. China
3. College of Chemistry and Chemical EngineeringLuoyang Normal University Luoyang 471022, P. R. China