Nanostructured SnO2 thin films were prepared by spraying tin chloride dihydrate onto the heated glass substrate at 250°C. The films were fired at 500°C. As-prepared thin films were studied using XRD and FESEM to know crystal structure and surface morphology. The average crystallite and grain size observed from XRD and FF-SEM was found to be less than 33 and 67？nm, respectively. The films sprayed for 30？min were observed to be most sensitive to H2S at 250°C. The results are discussed and interpreted. 1. Introduction The n-type semiconductor material has been widely used in the gas detecting field during the last decades. The sensing properties of various semiconductor oxides, especially the SnO2-based material, have been extensively studied [1]. Gas sensing applications demand materials that have a quick response-recovery time and high response for trace level detection of various gases. Semiconducting tin oxide is found useful for various gas sensing applications and improves its sensitivity and selectivity with appropriate catalysts [2]. Several potential applications have been reported previously, such as a transparent conductive electrode for solar cells [3], a gas sensing material for gas sensors devices [4], photochemical and photoconductive device, liquid crystal display [5], gas discharge display, and lithium-ion batteries. There has been intensive research on improving the gas response and selectivity by controlling the particle size [6], nanostructures [7], sensing temperature [8], surface structure [9], and catalysts [10]. A variety of techniques have been used to prepare tin oxide (SnO2) thin films. These include spray pyrolysis [11], ultrasonic spray pyrolysis [12], chemical vapour deposition [13], activated reactive evaporation [14], ion-beam-assisted deposition [15], sputtering [16], and sol-gel [17] methods. Among these techniques, spray pyrolysis has proved to be simple, reproducible, and inexpensive, as well as suitable for large area applications. Besides the simple experimental arrangement, high growth rate and mass production capability for large area coatings make it useful for industrial as well as solar cell applications. In addition, spray pyrolysis opens up the possibility to control the film morphology and particle size in the nanometer range. As demonstrated [18] spray pyrolysis is a versatile technique for deposition of metal oxides. Hydrogen sulfide is a toxic gas, often produced in coal, coal oil, or natural gas manufacturing. Even at low concentration it produces severe effects on the nervous system. Therefore, reliable
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