| Résumé | NO gas sensors, based on ZnO thin film (ZnO film), TiO 2 nanoparticulate film (TiO 2NP), and TiO 2NP/ZnO film double-layer film, were fabricated, and their sensing characteristics towards NO gas were investigated in this study. The maximal response of a ZnO film deposited onto a rougher Al 2O 3 substrate, towards NO gas, was higher than that of a ZnO film deposited on a smoother glass substrate. Although the sensing response of the TiO 2NPs itself towards NO gas was minute, the TiO 2NP/ZnO film double-layer film showed enhanced response as compared with TiO 2NP or ZnO film single-layer film. In addition, the sensor response of the TiO 2NP/ZnO film double-layer film was strongly influenced by the annealing time for the film preparation; the maximum response to NO was enhanced about 6.2 times as the annealing time was increased from 30 min to 2 h. Based on the XPS results, the increase in the transition zone between TiO 2NP and ZnO film along with the appearance of Ti 3+ state was noticed when the annealing time was increased. With the high sensitive TiO 2NP/ZnO film/Al 2O 3 electrode, the limit of detection (S/N = 3) can be achieved at 8.8 ppb. The double-layer TiO 2NP/ ZnO film also showed improved selectivities with respect to NO 2 and CO. © 2011 Elsevier B.V. |
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