Thickness-dependent dispersion parameters, energy gap and nonlinear refractive index of ZnSe thin films

[Display omitted] •Combined experimental and theoretical researches on ZnSe Thin Films.•The film thickness and refractive index were determined using envelope method.•The absorption coefficient and the energy gap were calculated.•Dispersion parameters were determined using Wemple-DiDomenico relation.•The third order susceptibility and nonlinear refractive index were calculated. Zinc selenide (ZnSe) thin films with different thicknesses were evaporated onto glass substrates using the thermal evaporation technique. X-ray diffraction analysis confirmed that both the film and powder have cubic zinc-blende structure. The fundamental optical parameters like absorption coefficient, extinction coefficient and band gap were evaluated in transparent region of transmittance and reflectance spectrum. The optical transition of the films was found to be allowed, where the energy gap increased from 2.576 to 2.702eV with increasing film thickness. Also, the refractive index value increase with increasing film thickness. The refractive indices evaluated through envelope method were extrapolated by Cauchy dispersion relationship over the whole spectra range. Additionally, the dispersion of refractive index was determined in terms of Wemple-DiDomenico single oscillator model. Third order susceptibility and nonlinear refractive index were determined for different thickness of ZnSe thin films.