本實驗以銀粒子修飾之氧化銦奈米材料，做為化學電阻式氣體感測器之感測材料，用於臭氧及二氧化氮氣體感測。比較銀修飾前後之感測效果，銀粒子於不同製程參數下之形貌及對感測的影響，也透過各項材料檢測，分析銀/氧化銦之物理、化學性質。於應用方面，本實驗針對六種氣體進行選擇性測試，並探討溼度對奈米複合材料之影響，並進一步進行一個月之穩定性測試。
首先以黃光顯影及電子束蒸鍍等製程，於矽基板上製作鈦金電極圖案，然後使用水熱法並經過鍛燒，合成得到磚形氧化銦粉末，並用噴塗方式將氧化銦粉末均勻分布於含有電極之矽基板上，形成約3 μm之薄膜。接著將此氧化銦薄膜浸入兩種不同濃度之硝酸銀還原溶液中，再利用254 nm之UV光源於氧化銦薄膜上沉積不同還原時間之銀粒子，並使用掃描式電子顯微鏡觀察各種參數下的材料表面形貌，銀粒子多呈現顆粒狀，尺寸落在200-500 nm之間。
藉由感測晶片對臭氧響應結果，篩選出以0.05 M之還原濃度還原1分鐘為最佳製程參數(以下以Ag (0.05 M-1 min)/In2O3表示)，並使用此樣品進行進一步之材料分析及進行其他氣體測試。以X光粉末繞射儀得到氧化銦為體心立方晶系之方鐵錳礦結構，並以化學分析電子能譜確認銀原子之存在及氧化銦之鍵結狀態，以及透過紫外光/可見光分光光度計及紫外光電子能譜瞭解氧化銦之能帶結構。
純氧化銦感測晶片於250 ppb臭氧下得到的響應約為415%，而Ag (0.05 M-1 min)/In2O3於相同濃度之臭氧下得到1136%之響應，證實銀的修飾確實提升感測的效果；Ag (0.05 M-1 min)/In2O3不僅於相同濃度之二氧化氮下得到1163%之響應，也進行甲醇、乙醇、甲醛、氨氣等氣體之選擇性測試，發現其對臭氧及二氧化氮之響應最好，選擇性比例約為1:1。此外也對Ag (0.05 M-1 min)/In2O3於不同溼度環境下進行測試，發現溼度越高，感測晶片的響應越低，但Ag (0.05 M-1 min)/In2O3即使於90%相對溼度下對250 ppb臭氧，仍有1057%響應，為正常溼度下響應的90%，顯示了Ag (0.05 M-1 min)/In2O3可於高濕度環境下工作的優勢。在進一步之Ag (0.05 M-1 min)/In2O3的一個月穩定性測試中，結果顯示其於第二週後的電流及響應皆能穩定維持，證明此感測晶片的高穩定性。

In this research, metal-oxide semiconductor gas sensors based on indium oxide nanobricks modified with silver nanoparticles, are reported for ozone and nitrogen dioxide gas sensing. Sensing performance of indium oxide with and without silver modification are compared, and effects of silver modification on gas sensing and morphology under various process parameters are also discussed. Physical and chemical properties of silver/indium oxide are further analyzed. In addition, gas selectivity comparison tests are investigated for six different gases, and the influence of humidity on nanocomposite materials and one-month duration stability test are employed for further investigation.
Firstly, gas sensor electrodes are made and defined on the silicon substrates by e-beam evaporation and then through photolithography processes. Indium oxide powders are obtained by a hydrothermal method and calcination, and then spray coated uniformly on prepared silicon substrate with sensor electrode, forming a thin indium oxide film around 3 um thickness. Silicon substrates with indium oxide film are then soaked in silver nitrate photoreduction solutions with two different concentrations, followed by illumination under a 254 nm UV light source for various photoreduction durations. Morphology of resulted thin film surfaces is further examined by scanning electron microscope. The silver particles are usually granular between 200 to 500 nm.
It is noted that silver deposition by photoreduction with 0.05 M solution for 1 min (denoted by Ag (0.05 M-1 min)/In2O3 in the following paragraph) produces best results by judging the response resulted toward ozone. Ag (0.05 M-1 min)/In2O3 sensor materials are further investigated by more material analysis and gas sensing tests. Utilizing X-ray diffraction, a body-centered cubic bixbyite-type crystalline structure is noted for indium oxide, and existence of silver atoms as well as bonding conditions of indium oxide are examined by X-ray photoelectron spectrometer. Moreover, ultraviolet-visible spectroscopy and ultraviolet photoelectron spectrometer are used to study the band structure of indium oxide.
Gas sensing test results show the response is 415% for pure indium oxide sensing chip under an environment with 250 ppb ozone, while the response is 1136% for Ag (0.05 M-1 min)/In2O3 under same experimental condition. This result illustrates improvement of sensing chip’s sensitivity by silver modification. Besides, the response is 1163% for Ag (0.05 M-1 min)/In2O3 under an environment with 250 ppb nitrogen dioxide, and it is further tested for methanol, ethanol, formaldehyde and ammonia, respectively. The final results indicate that Ag (0.05 M-1 min)/In2O3 has good sensitivity for both ozone and nitrogen dioxide, with the ratio about 1 to 1.
In case of humidity test, Ag (0.05 M-1 min)/In2O3 is tested under four different humidity conditions. It is found that gas sensing response decreases with increasing humidity. Although the sensing response is affected by increasing humidity, it is noted that Ag (0.05 M-1 min)/In2O3 gas sensor still keeps 1057% response value under 90% relative humidity with 250 ppb ozone environment. This result shows Ag (0.05 M-1 min)/In2O3 can function well under very high humidity environment as the resulted 1057% response value is as high as 90% of the response value under normal humidity. Moreover, after one-month duration stability test both gas sensing current change and response can still maintain at rather stable values after the second week, thus demonstrating high functionality and stability of Ag/In2O3 sensor materials.

摘要 i
Abstract iii
致謝 v
目錄 vi
圖目錄 ix
表目錄 xiii
第一章 緒論 1
1.1 前言 1
1.2 研究動機 2
第二章 文獻回顧 4
2.1 氣體感測原理 4
2.1.1氣體感測器概論 4
2.1.2金屬氧化物氣體吸附機制 7
2.1.3金屬氧化物與氣體化學吸附反應式 10
2.1.4金屬氧化物氣體脫附機制 12
2.2 氧化銦 15
2.2.1晶體結構 15
2.2.2合成方法與機制 17
2.2.3氧化鋅n型半導體特性 19
2.3 複合材料應用於氣體感測 22
2.3.1金屬奈米粒子 22
2.3.2氧化物 24
2.4 光還原法 26
2.4.1銀奈米粒子 26
第三章 儀器與研究方法 28
3.1 實驗架構 28
3.2 元件製作與材料合成 29
3.2.1基板電極製作 29
3.2.2磚型氧化銦合成 30
3.2.3感測元件製作 32
3.2.4奈米銀粒子製備 33
3.2.5元件組裝 34
3.3 感測材料分析 35
3.3.1掃描式電子顯微鏡 35
3.3.2熱重熱差同步分析儀 35
3.3.3 X光粉末繞射儀 37
3.3.4 紫外/可見光分光光度計 37
3.3.5化學分析電子能譜儀 38
3.4 氣體感測實驗架構 39
3.4.1臭氧感測系統 39
3.4.2二氧化氮感測系統 43
3.4.3臭氧溫溼度感測系統 47
3.4.4甲醇/乙醇感測系統 49
3.4.5甲醛/氨氣感測系統 50
第四章 結果與討論 52
4.1 材料分析 52
4.1.1熱重/差熱分析 52
4.1.2表面形貌 53
4.1.3元素分析 56
4.1.4晶體結構 59
4.1.5半導體性質 60
4.2 臭氧及二氧化氮感測結果 63
4.2.1磚型氧化銦與銀修飾 63
4.2.2不同濃度臭氧測試 66
4.2.3不同濃度二氧化氮測試 67
4.3 選擇性測試 69
4.3.1甲醇/乙醇感測 69
4.3.2甲醛/氨氣感測 70
4.3.3選擇性結果整理 71
4.4 環境因子對感測晶片之影響 73
4.4.1溼度效應 73
4.4.2穩定性測試 74
第五章 結論 76
參考文獻 78

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