INFLUENCE OF ROTATION RATE ON OPTICAL PROPERTIES OF ZnS THIN FILMS ANALYZED BY SPECTROSCOPIC ELLIPSOMETRY METHOD

Abstract

In the present work, zinc sulfide thin films were deposited on glass substrates by sol–gel process with different coating speeds 3600, 4800, 6000 and 7200[Formula: see text]rpm. Zinc acetate (Zn(CH3COO)[Formula: see text]H2O) and thiourea (CH4N2S) were used as precursors. Two-methoxyethanol and monoethanolamine were used as solvent and stabilizer, respectively. The optical properties of ZnS thin films such as refractive index, extinction coefficient, dielectric function and optical band gap energy of the films were obtained by spectroscopic ellipsometry (SE) analysis method in the wavelength range of 300–800[Formula: see text]nm. The incidence angle of the layers was kept at 70∘. The measured SE parameters [Formula: see text] and [Formula: see text] are fitted against the designed model by minimizing the mean square error (MSE). Considering the data obtained, it can be deduced that the optical properties of ZnS films are highly influenced by rotation rates. The extinction coefficients of the films were increased with increasing rotation rates of the films. From these results, it is found that the energy gap of the ZnS films increases with increasing rotation rates of the films in the range of 3.13–3.20[Formula: see text]eV.