Hindawi Publishing Corporation Journal of Nanomaterials Volume 2013, Article ID 146382, 8 pages http://dx.doi.org/10.1155/2013/146382 Research Article Influence of Annealing on Properties of Spray Deposited ZnO Thin Films Kalyani Nadarajah, Ching Yern Chee, and Chou Yong Tan Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur, Malaysia Correspondence should be addressed to Ching Yern Chee; chingyc@um.edu.my Received 8 August 2013; Revised 18 October 2013; Accepted 21 October 2013 Academic Editor: Mengnan Qu Copyright © 2013 Kalyani Nadarajah et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Zinc Oxide (ZnO) thin ilms were deposited on glass substrates via the spray pyrolysis technique. he ilms were subsequently annealed in ambient air from 300 ∘ C to 500 ∘ C. he morphology and structural properties of the thin ilms were studied by ield emission scanning electron microscope (FESEM), atomic force microscopy (AFM), and X-ray difractometry (XRD) techniques. Electrical resistivity of the thin ilms was measured using a data acquisition unit. he optical properties of the ilms were characterized by UV-vis spectroscopy and photoluminescence (PL) technique. X-ray difraction data showed that the ilms were grown in the (002) direction with a hexagonal wurtzite structure. he average grain size ranged from 15 to 27 nm. Increasing annealing temperatures resulted in larger grain sizes and higher crystallinity, with the surface roughness of annealed ilms being more than twice if compared to unannealed ilm. he electrical resistivity of the ilms decreased with the increasing annealing temperature. he UV and visible band emissions were observed in the photoluminescence spectra, due to exciton and defect-related emissions, respectively. he transmission values of the ilms were as high as 90% within the visible range (400–700 nm). 1. Introduction Currently, ZnO nanomaterials are being applied in electron- ics, photonics, catalysis, lighting, and chemical sensing. It is well known that ZnO exhibits many favorable properties, such as high chemical stability, wide bandgap of 3.37eV, high exciton binding energy of 60meV, and abundance in nature, and is also regarded as nontoxic [1, 2]. High- quality ZnO ilms are mainly fabricated by using physical and chemical methods. he physical methods include sputtering [3], molecular beam epitaxy [4], and laser ablation [5], while the chemical method includes spray pyrolysis [6], chemical vapor deposition (CVD) [7], sol-gel [8], spin coating [9], dip coating [10], and electrodeposition [11]. Most of the methods mentioned in the literature are not ideally suited for large area coatings. However, the spray pyrolysis method is one of the best methods to produce large area coatings based on the previous studies [3–11]. Additionally, it is simple, has low temperature deposition, is cost-efective, has good adhesion between ilms and substrate, and demonstrates uniform particle distribution, high purity, and excellent optical properties [12]. Some of the main factors afecting the properties of the ilm that uses spray pyrolysis technique are chemical solution (chemical composition, concentration), the distance between the substrate and atomizer interac- tion during ilm deposition, spray temperatures, substrate homogeneity, annealing conditions, and spray rates [13]. he spray pyrolysis method is eicient in producing thin ilm, multilayer ilm, thick ilm, and porous ilm on an inexpensive substrate [12]. Several oxides, such as ZnO [14], CdO [15], TiO 2 [16], SnO 2 [17], NiO [18], and Bi 2 O 3 [19], have been deposited using a spray pyrolysis method. his technique involves a water/alcohol solution of metal salts sprayed onto a heated substrate, followed by allowing it to decompose into an oxide ilm. he formation of oxide due to the decomposition reaction is thermodynamically feasible and leaves no residue on other reactants. he substrate temperature strongly afects ilm morphology. By increasing the temperature, the ilm’s morphology can be changed from a cracked to a porous structure [20]. he types and