Investigation of structural, morphological, and optoelectronic properties of ZnO thin films with Sn–Ni as co-doping

In this work, ZnO thin films with different concentrations of Sn–Ni as a co-doping have been synthesized using the sol gel method by dip-coating process. The X-ray diffraction (XRD) patterns demonstrated that undoped and co-doped ZnO thin films have crystalline nature with a hexagonal structure. Moreover, the crystallite size ( D ) exhibited a decreasing behavior due to the increasing doping ratio from 0 to 8 wt%, while the microstrain ( ε ) exhibited an increasing behavior. SEM micrographs demonstrated that undoped ZnO thin film has a homogeneous surface containing tiny spherical particles with an average size of less than 40 nm. Also, different sizes have been observed due to introducing Sn and Ni into ZnO thin films. Furthermore, the transmittance ( T %) of all thin films ranges from 90 to 83%. It was found that the transmittance ( T %) decreases due to the increasing co-doping ratio while the reflectance ( R %) increases. The bandgap energies ( E g ) values range from 3.24 to 3.07 eV . Moreover, the Wemple–DiDomenico (WDD), Sellmeier, Spitzer–Fan models, and Drude models have been used to estimate different optical parameters such as dispersion energy ( E d ), zero-frequency refractive index ( n 0 ) , zero-frequency dielectric constant ( ε 0 ) , the optical moment, high-frequency dielectric constant ( ε ∞ ), the density of state ( N c / m ∗ ) , relaxation time ( τ ), the optical mobility ( μ opt ) , and optical resistivity ( ρ opt ).