Structural, morphological, optical, and optoelectrical properties of SrZnO₂ thin films prepared by spray pyrolysis process

This work aims to examine the optoelectrical, optical, and structural properties of novel polycrystalline SrZnO₂ layers fabricated by a cost-effective nebulizer spray pyrolysis procedure at varying thicknesses (237, 395, 468, and 529 nm). The X-ray diffractograms have been used in this work to study the structure of the SrZnO₂ films. The SrZnO₂ films possessed an orthorhombic structure. The computational analysis involved determining the structural indices, including grain size, dislocation density, and lattice strain, of the SrZnO₂ films. Energy dispersive X-ray analysis has been used to verify the stoichiometry of these SrZnO₂ films. The surface morphology of the SrZnO₂ layers has been studied using the field-emission scanning electron microscope. The optical characteristics of the SrZnO₂ films have been investigated by the spectrophotometric measurements in the range 400–2500 nm. The optical results of the SrZnO₂ films depicted that the enhancement of the refractive index, Urbach's energy, and absorption coefficient of these films by boosting the thickness. Meanwhile, the improvement in the crystallization process led to a small decrease in the optical band gap energy values of the SrZnO₂ layers from 2.91 to 2.68 eV as the film thickness grew. Furthermore, the analysis of the optoelectrical characteristics of the SrZnO₂ films showed that the boost in film thickness enhanced the values of plasma frequency, optical resistivity, optical carrier concentration, optical mobility, and optical conductivity. The nonlinear optical properties of the SrZnO₂ layers have been boosted by the thickness growth. On the other hand, the hot probe equipment revealed that both the SrZnO₂ layers exhibited n-type semiconducting characteristics. The acquired results validate the wide bandgap semiconductor nature of these films. Consequently, it is advisable to use them as a window layer in various solar cell applications. The electrical results illustrated that the estimated activation energy of the SrZnO₂ films decreases as the thickness rises.