Influence of Zn and Cd doping on the optical properties of Se98Te2 thin films

Se₉₈Te₂ and Se₉₆Te₂X₂ (X = Zn or Cd) bulk samples were synthesized using the melt-quenching technique. Thin films of the samples with different thicknesses were deposited onto glass substrates by the means of thermal evaporation technique. The spectra of optical transmittance (T) and reflectance (R) were recorded over the wavelength range of 500–2500 nm using a Jasco V-570 double-beam spectrophotometer. Various optical parameters: including absorption coefficient, optical bandgap and refractive index were recorded. The nature of the optical transitions was determined. The findings reveal that the addition of Zn and Cd alters the optical band energy of the prepared thin films, with the highest bandgap observed in the undoped (base) sample, followed by the Zn-doped sample, and the lowest bandgap in the Cd-doped sample. This behavior may be attributed to the induced changes in local structural order and bonding environment. The oscillator strength (E_o), dispersion energy (E_d), and the static refractive index (n_s) were determined using Wemple–DiDomenico model. Moreover, the lattice dielectric constant \(\:\left({\epsilon\:}_{L}\:\right)\:\)and N/m* were estimated. This work provides valuable insights into tuning the optical behavior of chalcogenide based on SeTe thin films under the influence of Zn and Cd Doping for potential applications in optoelectronic devices.