Study of Mid-Infrared Optical Properties of ZnS Thin Films by Spectroscopic Ellipsometry

Abstract

ZnS films with different thickness were prepared on K9 glass substrate by electronic beam evaporation.They were denoted by A,B,C.The optical properties of thin films were studied by spectroscopic ellipsometry.The measured date of film A,B,C were fitted by Brendel oscillator,and based on ZnS film properties and the film forming characteristic of the ZnS film,building the model"substrate(K9glass)/EMA(50% K9 glass and 50% ZnS)/ZnS/rough surface layer(50% ZnS and 50%air)/air".The optical constants curve and thickness of ZnS thin film were got.The results show that the evaluation function MSE is small when Brendel model is used in data fitting.Within the wavelength range of 3000-12500 nm,the ZnS thin films refractive index and extinction coefficient are reduced with increasing wavelength.The extinction coefficient tends to zero near the long wavelengh.The thickness of ZnS measured value was closest to the theoretical value.The results have certain reference value to measurement and preparation of high quality ZnS thin film.