Structural and Optical Properties of ZnO Thin Films Deposited by Pyrolysis Spray Method: Effect of Substrate Temperature

Abstract

During the last decades, thin films of ZnO have given rise to a great interest, as transparent conducting oxides. This is due the optical and electrical properties of zinc oxide; it’s very high thermal and chemical stability, its non-toxicity as well as his abandonment in nature. The transparent conducting ZnO thin films were deposited on glass substrate by pyrolysis spray technique. Zinc acetate was used as starting solution with a molarity of 0.1 M. The structural and optical properties of the ZnO thin films were studied as a function of the substrate temperatures in the range of 100 to 400°C. Structural properties have been studied by X-ray diffraction (XRD) technique. The preferred orientation for ZnO thin films lies along (002) direction. From XRD data, the average crystallite size is determined from scherrer formula. The grain size is in the range of 10~27. The transmittance of the films is enhanced from 60 to 85% in the visible region in the range from 400 to 1100 nm by increasing the substrate temperature. The optical band gap energy attenuates from 3.67 to 3.25eV and whereas the Urbach energies of the films increase from 226 to 91.2 meV with increasing the substrate temperature from 100°C to 400°C.