Substituting Silver for Tellurium in Selenium–Tellurium Thin Films for Improving the Optical Characteristics

Abstract

The effect of Ag content on the linear and nonlinear optical characteristics of thermal evaporated Se90−xTe10Agx thin films, 100 nm thick, (where x = 0, 2, 4, 6, and 8 at.%) has been examined. The optical measurements were reviewed in the wavelength range of 390–2500 nm based on the transmittance and reflectance data, and the amorphous state of the as-prepared thin film was confirmed by X-ray diffraction. The absorption coefficient, extinction coefficient, bandgap, optical density, optical conductivity, dissipation factor, and other optical properties were examined and discussed. For all of the samples, the extinction coefficient of Se90−xTe10Agx declines as the wavelength and Ag concentration rise, whereas the absorption coefficient increases linearly with incident photon energy. Furthermore, the optical bandgap and the width of localized states alter in the exact opposite direction, which is consistent with previously reported findings. The decrease in the optical band gap as Ag concentration increases could be attributable to an increase in the amount of disorder in the materials and the density of defect states. Other critical optoelectronic characteristics are also determined, and they are found to be influenced by the Ag ratio and photon wavelength. These materials may be ideal for optical memory applications due to their high absorption coefficient and compositional dependence of absorption.