Nigerian Journal of Solar Energy, Vol. 26, 2015. © Solar Energy Society of Nigeria (SESN) 2015. All rights reserved. 71 Structural Properties of ZnO Thin Films Prepared by Spray Pyrolysis Method *Moreh, A.U., Momoh, M., Hamza, B., Argungu G.M. and Abdullahi, S. Department of Physics, Usmanu Danfodiyo University, Sokoto Nigeria Abstract - Zinc Oxide (ZnO) thin films were prepared on corning (7059) glass substrates by Spray Pyrolysis technique. The deposition was carried out at room temperature after which the samples were annealed in Nitrogen atmosphere at temperatures of 300°C and 400°C. The structural properties of ZnO thin films were studied by X-ray diffraction (XRD). The XRD analysis of the films showed that thin films are characterised by the appearance of (002) and (101) diffraction peaks. The intensity of the peaks was observed to increase with annealing temperature. The values of the lattice constants, a and c agree strongly with International centre for diffraction data (ICDD). Furthermore, the structural parameters such as micro-strain, dislocation density, full width at half maximum (FWHM) and grain size were found to be dependent on annealing temperature. Therefore the annealing effects on the structural properties of ZnO thin film will be useful for the formation of ZnO-based hetero-structure for application in fabrication of optoelectronic and other photovoltaic devices. Key words: ZnO, Spray Pyrolysis, Annealing, Lattice Parameters, Substrate Temperature 1.0 INTRODUCTION ZnO is an important wide band-gap optoelectronic material because it has high chemical and thermal stability at room temperature (27°C) and a large exciton binding energy of 60 meV. These characteristics made ZnO thin film a good candidate for ultraviolet emission applications (Mandalapu et al., 2008; Zhu et al., 2009). ZnO thin films usually show high transmittance in the visible range and possess excellent n-type conductivity when doped with Al, Ga and In, thus they can be used as transparent electrodes (Oh et al., 2006) and window layers of solar cells (Hagiwara et al., 2001). ZnO-based homostructure and heterostructure are attractively increasing attention because of their promising optoelectronics applications, and it is important work for the realization of ZnO optoelectric devices that to investigate the properties of ZnO films deposited various semiconductor substrates. ZnO has good lattice matching with the indium Phosphide (InP) crystal substrates, which has high solar conversion efficiency and high radiation resistance. Many growth methods such as, thermal oxidation (Rakhesh et al., 2009), Spin coating (Godbole et al., 2011), vacuum evaporation (Eya et al., 2006), electron beam evaporation (Rusu et al., 2011), sputtering (Janotti and Vande, 2008; Suchea et al., 2009), have been used in the preparation of ZnO thin films. The physical deposition routes have the advantages of producing high- quality materials, but also the disadvantage of the need for high temperature. Spray pyrolysis technology is a convenient chemical deposition method for the deposition of semiconductor thin films and has the *Corresponding author Tel: +234-8036029358 Email: abumoreh@yahoo.co.uk several advantages in comparison with other deposition techniques such as low cost of the source materials, producing high- quality films using comparatively simple deposition equipment, moderate substrate temperatures, deposition scaled for large area and uniform deposition with very thin layers with specific composition, morphology, good adhesion between the deposited film and controlling the shape and sizes. The morphology of the material depends on the thermal treatment. Usually, as-deposited films require a thermal treatment to improve stability and reduce the possible undesirable influence of the substrate. It has been reported previously that high-purity crystalline ZnO thin films can be fabricated by spray pyrolysis. The key success of spray pyrolysis is using a single-solid organic zinc fountain as a precursor with the physical and chemical properties required depositing a pure film at the substrate. Thermal annealing is a widely used method to improve crystal quality and to study structural defects in materials. During an annealing process, dislocations and other structural defects will move in the material and adsorption/decomposition will occur on the surface, thus the structure and the stoichiometric ratio of the material will change. Such phenomena can have major effects on semiconductor device properties, light emitting devices being particularly affected. In this paper, the preliminary results on the growth of ZnO thin films on glass substrates using hydrated zinc acetate [Zn (CH 3 COO) 2 . 4H 2 O] as precursor in ethanol with tri-ethylene glycol (TEG) is reported. The aim of the present study is to investigate the general features of the annealing effect of the prepared ZnO thin films. 2.0 MATERIALS AND METHOD Graded chemicals (Aldrich) were used for the