Synthesis, Characterization and Water Vapor Sensitivities of Nanocrystalline SnO 2 Thin Films
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Synthesis, Characterization and Water Vapor Sensitivities of Nanocrystalline SnO2 Thin Films M. Chacón, A. Watson, I. Abrego, E. Ching-Prado* Natural Science Department, Faculty of Science and Technology Technological University of Panama, Panama J. Ardinsson Development Center of Nuclear Technology (CDTN), Federal University of Minas Gerais, Bello Horizonte, Brasil
C. A. Samudio Pérez University of Passo Fundo, Porto Alegre, Brasil Abstract Thin films of SnO2 were prepared via wet chemical method and deposited by dip-coating on glass substrate. The annealing temperatures of the samples were 300, 400, 500 and 600o C, respectively. Water vapor sensor responses were measured and the experimental results are tested using the Freundlich model. The better water vapor sensitivities were obtained for annealing temperatures of 500 and 600oC, respectively. The samples were characterized morphological and structurally by SEM, XRD, Mössbauer spectroscopy and Raman spectroscopy. The fringes features in the ultraviolet-visible region indicate films thickness around 370 nm. The results are discussed in terms of the fine grain size of the samples. Introduction Research in semiconductor metal oxide nanocrystalline thin films is of great importance due to its wide range in technological applications, such as optoelectronic devices, fabricating solar cells, electrode materials for Li-batteries, and solid state gas sensor, among many others. Tin oxide (SnO2) is one of these materials that have been utilized as gas sensing due to a combination of its physical and chemical properties [1]. A disadvantage of currently conventional SnO2 gas sensors is that they typically operate at temperatures higher than 300ºC, which may cause structural changes and sensor instability. So that, fabricating sensing materials with low operating temperatures is desirable, because it permit the sensor work properly and reduce the energy consumption [1]. Furthermore, since the sensing mechanism of gas sensors is based on the chemisorption reactions that take place at the surface of SnO2, so increasing specific surface area of the sensitive materials leads to more sites for adsorption of surrounding gases. Some recent studies have been concentrated on improving gas sensitivity as well as reducing operating temperature by decreasing SnO2 size to nanoscale [1,2]. On the other hand, some important advantages of SnO2 are its stability in air, relative cheapness, and simplicity of preparation. Thus, tin oxide thin films have been grown for many relative no expensive preparation techniques, such as: sol gel, evaporation, hydrothermal, spray pyrolysis, etc [3]. Several behaviors of these tin oxide thin films have been observed to change by modifying the preparation method and environment condition. Actually, the use of polycrystalline SnO2 as solid state gas sensor is of great interest with regard to the relationship between electrical properties and crystalline size. In this paper
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nanocrystalline SnO2 thin films grown by liquid chemistry with samples anneale
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