高CO選擇比之PdO奈米片薄膜低溫氣體感測技術應用研究

Abstract

本計劃擬製備p-type氧化物半導體奈米結構薄膜，探討奈米結構薄膜在低溫氣體感測器(gas sensor)的應用，p-type氧化物包含PdO，NiO與Co3O4等，其中PdO將為主要之研究重點材料，我們利用活性濺鍍沉積法(reactive sputter deposition)製作氧化鈀(PdO)奈米片(nanoflake)結構薄膜，應用於低濃度CO與H2之低溫氣體感測器開發。PdO奈米片薄膜具有開放的巨大表面積，可以快速大量地吸附氣體分子，有利氣體感測效能。PdO對於CO氣體有相當複雜的感測行為，而對氫氣則有極度靈敏的響應。在本申請案中，我們將深入探討常溫至300oC溫度範圍內，PdO對CO與H2氣體感測響應機制，改進PdO感測效能；研究內容包括：(A) PdO對CO/乾空氣的感測機制，(B) PdO對H2氣的感測機制，及H2氣對CO感測行為的影響，並且研究(C) 濕氣對PdO氣體感測行為的影響；期望藉由這些研究成果建立PdO最佳化的CO感測條件。此外，本計畫將利用PdO在150oC時，對CO感應所顯現電導率反轉的特性，開發具電子鼻概念，高CO/H2選擇比的低溫PdO氣體感測器，我們將整合多個獨立操作於150oC及其他溫度的PdO感測元件於一個氣體感測器系統上，利用PdO對CO與H2氣體感測響應行為的差異，提升PdO的氣體感測選擇比。除了PdO奈米片薄膜，我們亦利用化學浴沉積法(chemical bath deposition)合成NiO與Co3O4奈米片薄膜，由於這兩種薄膜亦為p-type氧化物半導體，並呈現與PdO奈米片薄膜類似的形貌結構，有利提升氣體感測靈敏性與響應速率。我們將研究這兩種p-type氧化物半導體對各種還原性氣體的感測特性。

In this research, we will prepare nanostructured p-type oxide semiconductor thin films, and study their gas sensing behavior at low temperatures. This proposal will stress on the CO gas sensing of PdO thin films deposited on the silicon oxide substrate by reactive sputter deposition. The thin film has a nanoflake-like morphology, which provides an open surface with a tremendous area allowing for quick responses to gas adsorption. The PdO thin film has a complex gas sensing behavior toward CO, and exhibits a very sensitive sensing response to hydrogen. We will investigate the gas sensing response of the PdO nanoflake thin film to CO and H2 at temperatures below 300oC. The objectives of the research include (a) the study on the sensing mechanism of PdO toward CO/dry-air, (B) the study on the sensing mechanism of PdO toward H2 and the effect of H2 on the PdO sensing behavior toward CO, and (C) the effect of moisture on the PdO sensing behavior. PdO has an inversed change in the electrical conductivity upon the CO exposure. Based on this behavior, which is not observed for the sensing of other reductive gases, we will develop a CO gas sensing system of high CO selectivity. Several PdO sensing devices individually operating at 150oC and other temperatures will be integrated into one sensor system. In addition to the PdO nanoflake thin films, we will also synthesize low cost NiO and Co3O4 nanoflake thin films by chemical bath deposition for the study of the gas sensing characteristics of various reductive gases. Because these two oxides are p-type semiconductors and with a large open surface area as well , we expect that they have a similar sensing behavior toward reductive gases as the PdO nanoflake thin film at low temperatures.