本論文主要利用化學氣相沉積方式，在鍍於石英晶片上之金電極表面沉積二氧化銥，以此製作QCM質量式感測器，針對有機揮發性(VOC)氣體進行感測。我們發現，在IrO2上濺鍍金(Au)薄層，可以提高IrO2氣體感測器之靈敏度及應答速度。
二氧化銥成長部份，我們探討不同前驅物濃度與基板溫度對於二氧化銥成長的影響。發現沈積所得之IrO2有奈米管(nanotube)、奈米葉(nanoblade)、未完成之奈米管(incomplete-nanotube)、葉片多層柱(layered-column)等多種型態，在高前驅物濃度與高基板溫度下則形成薄膜(Film)。適合氣體感測的IrO2之沉積條件是：基板溫度約在350~ 400 ℃；前驅物溫度在80~95℃之間。
QCM感測部分，IrO2對酸類氣體的靈敏度最高，以丙酸而言，可偵測至20ppm以下。在可逆性方面，對胺類、醇類、芳香族類等之感測，都有部分不可逆現象，酸類氣體感測之則可逆性高達90%以上，尤以丙酸幾近完全可逆最高；在應答速度方面，以烷類之感測最快，t80在134-173 sec之間，丙酸感測之t80則為124sec。IrO2對酸類氣體，尤其是丙酸之感測，為靈敏度高、應答速度快之可逆吸附，具實用性。
金屬金對氣體感測之影響方面，濺鍍Au在IrO2上，感測辛烷及間二甲苯之靈敏度明顯提高，應答時間縮短。以感測1000ppm辛烷為例，訊號由35Hz增加至108Hz；t80由144sec縮短為90sec。研究顯示溅鍍金屬可增加IrO2感測靈敏度，加快應答速度，提高IrO2感測能力。
我們也以雙重吸附模式，分析IrO2對各種VOC氣體之恆溫吸附曲線，並計算Langmuir model中之特異性吸附位置Am與吸附常數KLangmuir，以及Henry model中之非特異吸附常數KHenry。
濺鍍金屬白金(Pt)在IrO2上，也跟金一樣，可以提高氣體感測靈敏度及應答速度。

In this thesis we investigated the metal organic chemical vapor deposition (MOCVD) deposition of iridium oxide onto the gold electrode on the piezoelectric quartz crystal for gas sensor. The gas sensing of volatile organic compound (VOC) was carried out with the quartz crystal microbalance (QCM) technique, and the effect of sputtered metal on the sensing property of IrO2 was also studied.

For the deposition, the effects of precursor concentration and substrate temperature (Ts) on the iridium oxide growth were investigated. We found that IrO2 exhibit several morphologies, such as nanotube, nanoblade, incomplete-nanotube, and layered-column, while the film structure was found at high precursor concentration and high substrate temperature. The deposition condition for IrO2, which was suitable for gas sensing, where found to be Ts=350-400℃, and the precursor reservoir temperature in the range of 80-90℃.

For QCM gas sensing, we found that IrO2 shows the high sensitivities for organic acid vapors. The sensing of the organic acid vapor s also shows fast response and high reversibility(>90%), while the amines irreversible. The sensing of the propionic acid vapor by IrO2 was found to be completely reversible, with the response time t80=124 seconds, and the detectable limit below 20 ppm.

When gold was sputtered on IrO2, we found that its VOC sensitivity and response speed were both improved, particularly for octane and m-xylene vapors. For example, in the sensing of the octane vapor, Δf of Au/IrO2 is 108 Hz vs. 35 Hz of IrO2, and t80 of Au/IrO2 is 90 sec vs. 144 sec of IrO2. Similar effect were also found for sputtered Pt.

We also use the two-step sorption model to analyze adsorption isotherm curves of various VOCs on IrO2. The number of specific adsorption site Am and the specific adsorption constant KLangmuir of the Langmuir model, as well as the non-specific sorption constant KHenry of the Henry model are calculated.

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