氧化鋅奈米柱因為表體效應已經被應用在氣體感測器上，而氧化鋅表面氧氣吸附和脫附會和奈米柱表面以及結構品質相關，為了區分氧化鋅內部還是表面的貢獻，此時需要利用一些工具來鑑定奈米柱表面的氧吸附。而二次諧波是對表面靈敏的一種量測方式，所以可以直接反映出奈米柱表面氧量的變化，在我們的研究中，二次諧波和其他量測工具如XPS、PL和XRD相結合，可以更了解氧化鋅氣體感測機制和奈米柱結構或表面品質的關係。
為了了解氧化鋅表面氧氣吸附的機制，我們選擇了三個不同的退火條件，藉由改退火溫度、退火系統中的氧壓力:(1) 改變退火溫度 (室內溫度, 200℃, 400℃ 和 600℃) 但維持相同的退火壓力 (2) 改變退火壓力 (25 mTorr, 55mTorr, 130mTorr and 180mTorr) 但維持退火溫度 (3) 改變退火環境 (真空或氧氣中) 且在 (600℃ 或 800℃)下，我們想要利用這些不同的退火條件，去改變氧化鋅奈米柱的表面狀態或是內部結構，當氧化鋅奈米柱的表面狀態或是內部結構改變時，氧化鋅表面吸附的氧離子數量將也會產生變化，而我們利用光激發發光光譜以及X射線繞射分析(002)峰的半高寬去分析氧化鋅奈米柱的表面狀態或內部結構，並且使用X射線光電子能譜和二次諧波的強度變化去量測氧化鋅的表面吸附氧離子照射紫外光脫附或在富含氧的環境下吸附的數量變化，藉由比較這些實驗數據，我們可以得到奈米柱內部結構和表面狀態以及奈米柱表面氧吸附量的關係，我們建立一個有效的方法去解釋奈米柱表面氧吸附量和其狀態的關係，而這個結果將會大大的影響氧化鋅氣體感測器的發展，因為氧化鋅奈米柱表面的氧離子是氣體感測器的反應中樞 (氣體感測器的機制是利用表面的氧離子去和感測氣體反應而改變氧化鋅的特性)。

ZnO nanorods have been applied to be a gas sensor as their high surface to volume ratio. Oxygen absorption and desorption on ZnO nanorods should depend on the quality of surface and bulk ZnO nanorods. In order to distinguish the contribution from the surface or bulk of ZnO nanorods, there should be available tools to inspect the change amount of oxygen absorption on ZnO nanords through post-treatment. Second harmonic generation (SHG) has high sensitivity on the surface variation and reflects to the actual amount of oxygen adsorption on ZnO nanorods. In this work, SHG is used to consist with the measurement of XPS, PL and XRD for realizing the mechanism of gas sensor made of ZnO nanorods and the correlation between the surface or bulk quality of nanorods.
In order to study the mechanism of oxygen absorbed on ZnO nanorods, we choose the three different annealing conditions by different annealing temperature and oxygen pressure in the annealing chabmer. (1) changing the annealing temperature (room temperature, 200℃, 400℃ and 600℃) in oxygen gas but fixing the annealing pressure (2) changing the annealing pressure (25 mTorr, 55mTorr, 130mTorr and 180mTorr) but fixing the annealing temperature (3) changing the annealing ambient (vacuum or oxygen) at (600℃ or 800℃) in which these annealing conditions were tuned to change the surface states or structure of zinc oxide nanorods. When the surface states or structure of ZnO nanorods is changing, the amounts of oxygen absorbed on the surface of ZnO nanorods will follow the change. We use the PL spectrum and FWHM of (002) peak in XRD to study ZnO nanorods surface states and structure and the XPS spectrum and the changing of SHG intensity to measure the changing of amounts of oxygen absorbed on the ZnO nanorod surface which caused by irradiating UV light irradiation or exposing rich oxygen. We compare these results of these measurements with each others and we obtain some relationships between the surface states or structure of ZnO nanorods and the amounts of ZnO nanorods surface oxygen. We built the effective method to explain the amounts of ZnO nanorods surface oxygen and its states. This result will be important influence to develop ZnO gas sensor because oxygen ions on the ZnO nanorods surface are the reaction center (the mechanism of gas sensor is that the surface oxygen ions react with the sensing gas and then change its characteristic).

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