氧化鋅奈米片薄膜應用於一氧化碳氣體感測之特性研究

Abstract

氧化鋅奈米結構由於在化學環境中具有高的靈敏度，故被廣泛地運用於氣體感測上。在本研究中，我們利用簡單且易操作的化學浴沉積法，以醋酸鋅為前驅物，甲醇為溶劑，合成出獨特的氧化鋅奈米片狀結構。氧化鋅奈米片薄膜在真空環境與大氣環境下進行的一氧化碳感測，感測溫度相較一般的氣體感測器為低。我們利用X光分析儀(XRD)、掃描式電子顯微鏡(SEM)和穿透式電子顯微鏡(TEM)分析氧化鋅奈米片薄膜的微結構特性，並且利用化學分析電子儀(ESCA)研究試片的表面化學成分。在真空中進行一氧化碳感測之氧化鋅奈米片薄膜，其成長條件為沉積濃度0.15M的醋酸鋅溶液，沉積時間為32小時，經過350oC鍛燒之氧化鋅薄膜。當一氧化碳吸附在氧化鋅奈米片薄膜表面時，感測到的電流值增加。在真空中，感測溫度100oC對一氧化碳有最佳的感測反應。當感測溫度為200oC，一氧化碳將持續的與氧化鋅反應，並將氧化鋅還原成金屬鋅。在大氣下氧化鋅的一氧化碳感測響應值隨著一氧化碳的濃度提高而增加，且感測溫度200oC時有最佳的感測反應，可測得的最低濃度為2500 ppm。在進行一氧化碳感測後，經由XRD與ESCA的分析結果可得知，氧化鋅奈米片薄膜具有良好的再使用性。

Znic oxide nanostructures have attracted much attention in gas sensing technology because of their high sensitivity to the chemical environments. In this research, we synthesized flake-like ZnO nanocrystals by chemical bath deposition method using znic acetate as the precursor and methanol as the solvent. The study on CO sensing by the ZnO nanoflake thin film were conducted under vacuum and atmosphere conditions at relative low sensing temperatures. The microstructure of ZnO nanoflake thin films was examined by using X-ray diffraction (XRD), scanning electrion microscopy (SEM), transmission electron microscope (TEM), and the surface chemical composition was analyzed by electron spectroscopy for chemical analysis technique (ESCA). The CO sensing study under vacuum shows that the electrical current increases when ZnO nanoflake thin films which was deposited on the Si substrate in 0.15 M znic acetate solution and calcined 350oC. The ZnO thin film has the best CO sensing performance at 100oC with a good reproducibility. At 200oC, the surface of ZnO nanoflake is reduced to metallic Zn. Under the atmosphere condition, the sensing response increase with the CO gas concentration. The best CO sensing performance was found to be at 200oC with a detection limit of 2500 ppm. After the CO sensing test in atmosphere, microstructure and chemical properties of the ZnO nanoflake thin films are intact according to XRD and ESCA analyses after the CO sensing test, and thus the sensing performance is highly reproducible in atmosphere.