Optical constants and fitted transmittance spectra of varies thickness of polycrystalline ZnSe thin films in terms of spectroscopic ellipsometry

Highlights: ► Different thicknesses of ZnSe films were prepared. ► The microstructure parameters of the films have been determined. ► Spectroscopic ellipsometry parameters were analyzed to determine the optical constants. ► Transmittance spectra has been simulated using Murmann's exact equation. -- Abstract: Different thickness of Zinc selenide (ZnSe) thin films were deposited onto glass substrates by the thermal evaporation technique. Their structural characteristics were studied by X-ray diffraction (XRD). The microstructure parameters, crystallite size and microstrain were calculated. The optical constants (n, k) and film thicknesses of ZnSe thin films were obtained by fitting the ellipsometric parameters (ψ and Δ) data using three layer model systems in the wavelength range 300–1100 nm. It is found that the refractive index, n increases with the increase of the film thickness. The possible optical transition in these films is found to be allowed direct transitions. The optical energy gap increase with increasing the film thickness in a narrow range. The experimental transmittances spectrum can be fitted in terms Murmann's exact equation using the modeled thickness and optical constants obtained spectroscopic ellipsometry model