Optical constants, dispersion parameters and non-linearity of different thickness of As40S45Se15 thin films for optoelectronic applications

The present work investigates the structural parameters of As40S45Se15 glassy alloy and optical properties of its thin films. As40S45Se15 thin films with different thickness (d = 120, 350, 500, 700, 850 and 1000 nm) have been deposited on glass substrates. The association of optical properties with changes in thickness of As40S45Se15 thin films was investigated in the spectral range of transmittance between 400 and 2500 nm. The thin films thickness was calculated using Swanepoel method. The optical constants, dielectric constants, dispersion parameters were computed. The analyses of the absorption spectra of As40S45Se15 thin films indicate the existence of an indirect optical transition mechanism. With increasing the films thickness, the absorption coefficient and optical bandgap were decreased, while Urbach energy, the values of refractive index (n) and the extinction coefficient (kex) were increased. The dispersion of the refractive index is described using the Wimple–DiDomenico (WDD) single oscillator model and the dispersion parameters were computed as a function of thickness films. The optical constants, optical dielectric constants, optical conductivity, electrical susceptibility, and non-linear refractive index were investigated and discussed.