Structural, morphological and optical properties of Sn doped zinc oxide thin films synthesis by sol-gel method for photocatalytic applications

Undoped and tin (Sn)-doped ZnO thin films were synthesized via sol-gel technique and deposited onto the glass substrates using the spin-coating technique. The impact of Sn incorporation at various concentrations on the structural, morphological, and optical properties of ZnO films was studied x-ray diffraction revealed a hexagonal crystal structure for all samples with a preferential crystalline orientation along the (002) plane. The transparency of Sn-doped ZnO thin film in the visible region significantly increased from 75% to 90%. The morphological analysis revealed a decrease in the grain size from 21 nm to 15 nm with Sn content in the matrix of ZnO. The optical properties reveal the contribution of the Burstein-Moss effect and electron-impurity scattering to slightly widen the bandgap from 3.22 eV to 3.24 eV. Urbach energy values demonstrated that the presence of Sn dopant increased the tail-band width of the localized states. These observations suggest that the deposited Sn-ZnO thin films could have possible applications as a photocatalyst for methylene blue (MB) dye degradation.