Improvements of multifunctional spintronic and optoelectronic applications of nanostructured Eu-doped ZnS thin films through magnetic and linear, nonlinear optical investigations

Abstract

This study describes the spintronic and optoelectronic improvements upon Eu substitution in Zn atomic site of the nanostructure ZnS thin films. The electron beam deposition technique has been used to deposit a series of Zn1-xEuxS thin films on a glass substrate with different Eu dopants (x = 0, 0.01, 0.03, 0.05, and 0.08). The nanostructure nature of the Eu-doped ZnS thin film has been confirmed from structural and morphology studies performed by the X-ray diffraction (XRD) and atomic force microscope (AFM) measurements. XRD investigations further show a hexagonal-type structure with no detectable extra phases with the lattice parameter c increasing, while a decrease linearly with increasing Eu-dopant in the ZnS hosted lattice. The microstructures analysis reveals a reduction in the mean crystallite size and increasing in the lattice strain of the films with rising Eu doping. The Fourier transform infrared spectra display the existence of chemical bonds in the thin films whereas photoluminescence reveals near-band edge emission. The linear optical parameters were obtained from the analysis of the transmission data measured by the spectrophotometer technique. The results reveal that the band gap energy (EgOpt) reduces by raising ohe Eu doping ratio, which is ascribed to the structural deformation (strain and/or defects) confirmed from structural analysis, density of localized states and PL measurements. The index of refraction n was calculated using the Swanepoel method. The values were found to increase as the level of Eu doping grows, which is associated with the rise in polarizability. Wemple and DiDomenico's (WDD) model was utilized to compute the dispersive and oscillator energies (Eo, and Ed), the nonlinear absorption coefficient βc, nonlinear refractive index n2, and nonlinear optical susceptibility χ3. The results demonstrate that the adjustability of EgOpt , Eo, and Ed of ZnS: Eu films is conducted to improve the nonlinear optical characteristics, providing it well-suited for optoelectronic device implementations. On the other hand, ZnS doped with Eu film displays inherent ferromagnetic properties at room temperature, as evidenced by the results of the magnetic investigation. This finding could be attributed to the presence of sulphur defects (vacancies), as supported by photoluminescence (PL) measurements, which lead to the creation of the bound magnetic polaron. These discoveries indicate the potential of utilizing Eu-doped ZnS film in the effective development of spintronic devices.