Optical study of thin (As 2 Se 3 ) 1-x (AgI) x films

The optical properties of chalcogenide thin films from the pseudo-binary (As 2 Se3) 1-x (Agl) x system, where x=5, 10, 15, 20, 25, 30 and 35 mol.% were studied with respect to the influence of Agl incorporation. Two techniques - vacuum thermal evaporation (VTE) and pulsed laser deposition (PLD) were applied to prepare the films. The films were amorphous, as revealed by X-ray diffraction (XRD); their morphology and topography studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) exhibited uniform homogeneous surfaces. The optical transmission and reflection of the deposited (As 2 Se 3 ) 1-x (Agl) x were investigated in the spectral region 300-3300 nm. The values of the optical parameters (refractive index, n, and extinction coefficient, k) were determined from the spectra. The compositional dependence of the basic optical parameters of the films, specifically their dependence on different Agl contents, was determined. The optical band gap Eg was determined from the Tauc plot ahv=B(Eg - hv) 2 and the Eg 04 in the strong-absorption region (α ≥10 4 cm -1 ) from the relationship α= f (hv). The dispersion of the refractive indices and extinction coefficients and the observed trends in the band gap variation were discussed with respect to the influence of the Agl and film preparation methods.