Chemical Bath Deposition Grown ZnO Thin Films: Role of Manganese Doping

In this study, the effect of manganese (Mn) doping concentration (0.0, 0.2, 0.4, 0.6, and 0.8 M) on the structural, microstructural, linear, and nonlinear optical properties of zinc oxide (ZnO) thin films grown by chemical bath deposition method was investigated. X-ray diffraction (XRD) analysis revealed that ZnO films had a polycrystalline hexagonal structure with the predominance of the (101) plane. The field emission scanning electron microscopy (FESEM) images picturized irregular-shaped particles. Undoped ZnO film showed agglomerated spherical nanoparticles while that of 0.8 M Mn-doped ZnO indicated the floral pattern. Linear and nonlinear optical parameters were evaluated using transmittance and absorbance measurements. The optical band gap energy of Mn-doped ZnO films for direct transition was estimated in the range of 2.87-3.10 eV. The values of the refractive were determined both from the optical bandgap using the Moss relation, Herve and Vandamme relation, & Ravindra and Gupta's relation. Linear optical properties of the films such as optical dielectric constants, volume energy loss functions, and optical conductivity were studied. The result showed that the linear optical properties were affected by Mn-doped ratios. It was determined that nonlinear optical properties such as first-order chi(1) susceptibility part, third-order chi(3) nonlinear susceptibility part, refractive index (n(2)), and optical electronegativity (eta(opt)) of the ZnO film were also affected by the Mn doping process.