Electronic excitation induced structural, optical and electrical properties of Se85S10Zn5 thin films and applicability of a single oscillator model

Abstract

The effect of electronic excitation induced by 120 MeV Ag⁹⁺ ion irradiation on the structural, optical and electrical properties of Se₈₅S₁₀Zn₅ thin films has been investigated at various ion fluencies. Thin films of Se₈₅S₁₀Zn₅ have been prepared by vacuum evaporation technique with thickness ∼250 nm on cleaned glass substrates. X-ray diffraction (XRD) patterns confirm that preferred crystallite growth occurs in the (100) plane corresponding to the hexagonal phase structure. XRD analysis also shows that the crystallite size decreases with increasing ion fluence. This post irradiation change was also supported by morphological studies carried out by scanning electron microscopy (SEM) which indicate the grain fragmentation process has been taking place due to excessive energy deposition during the passage of ion beams. The optical parameters calculated from optical transmission spectra in the wavelength range 200–1000 nm show the reduction of the optical band gap and an enhancement in absorption coefficient after ion irradiation. The data from refractive index dispersions of the thin films before and after irradiation fit well with a single oscillator model. This post irradiation change in the values of optical parameters suggests that the investigated material may have industrial applications for various optoelectronic devices. Electrical properties such as dc conductivity of investigated thin films were carried out in the temperature range 309–370 K. Analysis shows that the value of the activation energy decreases with the increase of ion fluence indicating that the density of defect states increases after swift heavy ion irradiation.