Effect of Mn doping on the structural and optical properties of ZnO films
Y. Caglar, S. Ilican, M. Caglar, F. Yakuphanoglu
Anadolu University, TR
Keywords: Mn doped ZnO, sol-gel spin coating, optical band gap, urbach energy.
Abstract:Undoped and Mn-doped ZnO films were deposited by the sol–gel method using a spin-coating method. The structural and optical properties of undoped and Mn-doped ZnO films were studied. Zinc acetate dehydrate, 2-methoxyethanol and monoethanolamine were used as a starting material, solvent and stabilizer, respectively. The dopant source is manganese acetate tetrahydrat. The Mn/Zn ratio was 1 %., 3 %. and 5 %. The crystal structure and orientation of the thin films were investigated by X-ray diffraction patterns. X-ray diffraction patterns confirm that the films have polycrystalline nature. The thin films have (002) as the preferred orientation. The information on strain and crystallite size was obtained from the fullwidths-at-half-maximum (FWHM) of the diffraction peaks. Transmittance spectra of the films were recorded on UV spectrophotometer in the spectral ranging from 190 to 900 nm. The reflectance measurements of the films were carried out with constant angle specular reflection attachment. The optical band gap, Urbach energy and optical constants of the films were evaluated as dependent on the Mn incorporation. The values of the direct band gap change with Mn content. The shift of absorption edge is associated with Burstein-Moss effect. Urbach energy of the films changes inversely with optical band gap.