Gas sensing properties of nanostructured MoO₃ thin films prepared by spray pyrolysis

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• 作者：H.M. Martí ; nez^a ; J. Torres^a ; M.E. Rodrí ; guez-Garcí ; a^b ; L.D. L&oacute ; pez Carreñ ; o^a ; ^{ldlopezca@unal.edu.co}
• 关键词：MoO3 ; Spray pyrolysis ; Gas sensor ; H2O ; CO
• 刊名：Physica B
• 出版年：2012
• 期刊代码：53_09214526
• 类别：ph
• 出版时间：15 August, 2012
• 卷：407
• 期：16
• 页码：3199-3202
• 文件大小：600 K

摘要

Thin films of molybdenum trioxide (MoO₃) were deposited on common glass using the chemical spray pyrolysis technique. A (NH₄)₆Mo₇O₂₄4H₂0 solution 0.1 M was used as the precursor one. The influence of substrate temperature on the crystallographic structure, surface morphology and electrical behavior of MoO₃ thin films was studied. MoO₃ can exist in two crystalline forms, the thermodynamically stable orthorhombic 伪-MoO₃ and the metastable monoclinic 尾-MoO₃ phase. XRD-spectra showed a growth of 伪-MoO₃ phase percentage as substrate temperature increases from 420 K up to 670 K. Films deposited in the 500-600 K range have a clearly porous surface structure of nanometer order as can be seen in SEM images. Changes up to six magnitude orders were observed in MoO₃ thin films electrical resistance when films temperature varied from 100 K up to 500 K. The sensing property of these MoO₃ films was also studied. The sensitivity was investigated in the temperature range 160 and 360 K for H₂O and CO gases, respectively. Both of them are of reducing nature. In all studied cases sensitivity decreases slowly as film temperature is raised. At room temperature the sensitivity changes from 12 up to 75%depending on substrate temperature. The sensitivity for CO gas was found to be lower than that of H₂O.