Abstract In this study, a two-layered thin-film structure consisting of a dispersed nanoscaled Ag2O phase and SnO2 layer (SA) and a mono-composite film layer (CSA) consisting of a nanoscale Ag2O phase in the SnO2 matrix are designed and fabricated for NO2 gas sensor applications. Two-layered and mono-layered SnO2–Ag2O composite thin films were synthesized using two-step SnO2 and Ag2O sputtering processes and Ag2O/SnO2 co-sputtering approach, respectively. In NO2 gas-sensing measurement results, both SA and CSA thin films that functionalized with an appropriate Ag2O content exhibit enhanced gas-sensing responses toward low-concentration NO2 gas in comparison with that of pristine SnO2 thin film. In particular, a gas sensor made from the mono-composite SnO2–Ag2O layer demonstrates apparently higher NO2 gas-sensing performance than that of double-layered SnO2–Ag2O thin-film sensor. This is attributed to substantially numerous p–n junctions of Ag2O/SnO2 formed in the top region of the SnO2 matrix. The gas-sensing response of the optimal sample (CSA270) toward 10 ppm NO2 gas is 5.91, and the response/recovery speeds in a single cycle dynamic response plot are 28 s/168 s toward 10 ppm NO2, respectively. Such a p–n thin-film configuration is beneficial to induce large electric resistance variation before and after the introduction of NO2 target gas during gas-sensing tests. The experimental results herein demonstrate that the gas-sensing performance of p–n oxide composite thin films can be tuned via the appropriate design of composite thin-film configuration.

中文翻译：

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用于 NO2 气体传感应用的 SnO2-Ag2O 复合材料的薄膜结构设计

摘要 在这项研究中，设计和制造了由分散的纳米级 Ag2O 相和 SnO2 层 (SA) 组成的两层薄膜结构和由 SnO2 基体中的纳米级 Ag2O 相组成的单复合薄膜层 (CSA)。用于 NO2 气体传感器应用。分别使用两步 SnO2 和 Ag2O 溅射工艺和 Ag2O/SnO2 共溅射方法合成了两层和单层 SnO2-Ag2O 复合薄膜。在 NO2 气敏测量结果中，与原始 SnO2 薄膜相比，用适当的 Ag2O 含量功能化的 SA 和 CSA 薄膜对低浓度 NO2 气体表现出增强的气敏响应。尤其是，由单复合 SnO2-Ag2O 层制成的气体传感器表现出明显高于双层 SnO2-Ag2O 薄膜传感器的 NO2 气体传感性能。这归因于在 SnO2 基体的顶部区域中形成了大量的 Ag2O/SnO2 p-n 结。最佳样品 (CSA270) 对 10 ppm NO2 气体的气敏响应为 5.91，单循环动态响应图中的响应/恢复速度分别为 28 s/168 s 对 10 ppm NO2。这种 ap-n 薄膜配置有利于在气敏测试期间在引入 NO2 目标气体之前和之后引起较大的电阻变化。本文的实验结果表明，可以通过适当设计复合薄膜结构来调整 p-n 氧化物复合薄膜的气敏性能。