thin films have been deposited on glass substrates at substrate temperature 400°C through nebulizer spray pyrolysis technique. X-ray diffraction (XRD) analysis shows that the films structure is changed from hexagonal to tetragonal. The high-resolution scanning electron microscopy (HRSEM) studies reveal that the substrate is well covered with a number of grains indicating compact morphology with an average grain size 50–79?nm. Energy dispersive X-ray analysis (EDAX) reveals the average ratio of the atomic percentage. Optical transmittance study shows the presence of direct transition. Band gap energy decreases from 3.33 to 2.87?eV with respect to the rise of Sn content. The electrical resistivity of the thin films was found to be 106?Ω-m. 1. Introduction Recently, the application range of semiconductor gas sensors prepared out of metal oxides such as ZnO, TiO2, CdO, SnO2, and In2O3 is spreading more to detect the pollutants, toxic gases, alcohol, and food freshness. It is known that the electrical conductivity of semiconductors like ZnO, SnO2 and CdO increases while they form compounds like Sn substituted CdO and Sn substituted ZnO. These materials find applications in sensing devices like gas sensors, moisture detectors, and electronic sensors [1–4]. At present, research interest has been shifted to thin film sensors [5]. Sn substituted ZnO is sensitive to many gases like hydrocarbons [6], H2 [7], oxygen [8], and so forth and also has satisfactory stability. Sn substituted ZnO thin films can be prepared by a variety of techniques, such as low-temperature ion exchange method [9], coprecipitation method [2], and thermal evaporation [10]. Nebulizer spray technique is widely used because it is simple and economically viable technique, which produces films of good quality for device applications. The preparation method for sensing material therefore plays an important role in the morphological characteristics and control over the particle size and surface area of the sensor. In the present work, preparation and characterization of ZnSnO3 thin films by simple and low cost nebulizer spray pyrolysis technique have been reported. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), CO gas sensitivity, electrical conductivity, and optical measurements. The results are discussed and reported. 2. Experimental Technique Chemicals used for the deposition of were analytical grade zinc chloride, tin (IV) chloride, sodium hydroxide pallet, ethylene diamine tetraacetic acid salt (EDTA), and
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