Physical, linear and nonlinear optical properties of amorphous Se_90-xTe₁₀M_x (M = Zn, In, Pb, x = 0, 5) chalcogenide thin films by electron-beam deposition

Amorphous Se₉₀Te₁₀ and Se₈₅Te₁₀M₅ (M= Zn, In, Pb) were deposited as thin films on glass substrates by electron-beam evaporation. The effect of Zn, In and Pb incorporated at the expense of Se on optical and physical properties of chalcogenide Se₉₀Te₁₀ were investigated and results were correlated. The transmission and reflectance spectra of the samples were used to deduce some dispersive linear optical constants which were studied from 250 to 2500 nm. The optical gap was evaluated through extrapolation of the Tauc plot in the strongly absorbing region and based on the Wemple-DiDomenico single oscillator model. Ideas from the chemical bond approach and consideration of disorders emanating from localized states in the mobility gap were employed to explain the optical trends. Some dielectric and nonlinear optical parameters including nonlinear refractive index and susceptibility of the thin films were calculated.