Abstract Poor selectivity has always been the most severe challenge in the practical applications of gas sensors based on metal-oxide semiconductors (MOSs). It is difficult to distinguish CO and H2 because of the cross-sensitivity phenomenon. Herein, a series of n-ZnO/p-xCo3O4 NPs (1:x represents the molar ratio of Zn:Co) was prepared through a simple sol-gel method. Structural and material characterization were performed via X-ray diffraction (XRD) and transmission electron microscopy (TEM), while other techniques were used to assess the gas-sensing properties. The characterization results indicated that the oxides in the n-ZnO/p-0.61Co3O4 NPs formed p-n heterojunction instead of being dissolved together. The gas sensing results confirmed that the Zn:Co molar ratio influenced the gas-sensing selectivity of the n-ZnO/p-xCo3O4 NPs. Interestingly, regarding the gas-sensing behavior of n-ZnO/p-0.61Co3O4 NPs, the overall conductance of the film decreased in the presence of CO and increased in the presence of H2 at the testing temperature of 350 °C. This paper provides an approach to address the problem of poor selectivity of MOS-based gas sensors.

中文翻译：

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n-ZnO/p-Co3O4 传感器对均质还原气体的气敏选择性

摘要 选择性差一直是基于金属氧化物半导体（MOS）的气体传感器实际应用中最严峻的挑战。由于交叉敏感现象，很难区分 CO 和 H2。在此，通过简单的溶胶-凝胶法制备了一系列 n-ZnO/p-xCo3O4 NPs（1:x 代表 Zn:Co 的摩尔比）。通过 X 射线衍射 (XRD) 和透射电子显微镜 (TEM) 进行结构和材料表征，而其他技术用于评估气敏特性。表征结果表明，n-ZnO/p-0.61Co3O4 NPs 中的氧化物形成了 pn 异质结，而不是溶解在一起。气敏结果证实 Zn:Co 摩尔比影响 n-ZnO/p-xCo3O4 NPs 的气敏选择性。有趣的是，关于 n-ZnO/p-0.61Co3O4 NPs 的气敏行为，在 350 °C 的测试温度下，薄膜的总电导在 CO 存在下降低，在 H2 存在下增加。本文提供了一种解决基于 MOS 的气体传感器选择性差的问题的方法。