現今社會對公共安全和環保之重視日益漸增，對於各種污染性氣體之排放和濃度規範皆有立法規定，因此對各種污染性氣體偵測的需求也日益漸增。乙醇為易揮發性液體且易燃，過量的乙醇蒸氣，對人體健康有害，因此在交通安全防護、實驗室、工業環境都需要偵測其含量。金屬氧化物半導體為現今應用最普遍、最廣泛使用之氣體感測材料，其中包括二氧化錫（SnO2），利用二氧化錫在不同氣氛中電阻變化之特性，可偵測氧化性氣氛及還原性氣氛。二氧化錫可還藉由添加其他物質以增進對特定氣體的感測能力。
本研究嘗試使用反應性射頻磁控濺鍍法製備SnO2：Mo薄膜，研究Mo的添加對乙醇蒸氣感測性能的影響。在固定工作壓力7 mtorr下，利用尋找SnO2薄膜最佳氣體感測性質之O2流量分率，再以此O2流量分率製備SnO2：Mo薄膜，Mo之含量為利用Mo靶濺鍍槍之功率大小加以控制，並研究退火製程溫度對薄膜氣體感測性質之影響。薄膜結構以低掠角X-ray繞射儀（GIAXRD）分析，薄膜表面型態及表面粗糙度（Rrms）以場發射型掃描式電子顯微鏡（FE-SEM）、原子力顯微鏡（AFM）觀察，薄膜成分及化學鍵結以X-ray光電子能譜儀（XPS）分析，並以本實驗室組裝之氣體感測儀器量測電性及氣體感測性質。
研究結果顯示，SnO2薄膜氣體對100 ppm乙醇氣氛感測性質最佳之O2流量分率為35%，最佳操作溫度為450℃，而最佳之退火製程為溫度500℃，持溫時間四小時。
以O2流量分率35%，製備不同Mo含量之SnO2：Mo薄膜之研究結果顯示：Mo之添加，在SnO2晶格中產生固溶，使結構產生變化，晶粒、表面叢集成長受到抑制，使薄膜結晶性、表面粗糙度隨Mo添加量上升而下降。SnO2：Mo薄膜氣體對100 ppm乙醇氣氛感測性質最佳之條件為：Mo靶濺鍍槍功率為60W，靈敏度最大值出現在操作溫度400℃時，而最佳之退火製程為溫度500℃，持溫時間四小時。
SnO2薄膜氣體感測器對其他還原性氣氛之氣體感測性質相似，選擇性不佳，而SnO2：Mo氣體感測薄膜存在對乙醇氣氛之選擇性。

There is an increasing importance about public safety and environmental protection nowadays. Air pollutions are prohibited and demands for detecting pollution gases are increased. Ethanol is evaporable and flammable at room temperature. Excessive ethanol vapor are harmful to human. Determination of the content of ethanol vapor in atomosphere is necessary in experimental and factory area and for traffic safety protection.
Metal oxide semiconductors（MOS） are the most widespread gas sensing materials, tin oxides（SnO2） are included. One of the characters of SnO2 is its resistivity changes when exposuring in reducing and oxidizing gases. By measuring the changes of resistivity, we can determine the existence and concentration of reducing and oxidizing gases. Adding other materials into SnO2 matrix can improve the sensing ability and selectivity to specific gases.
We tried to prepare SnO2：Mo thin films by reactive RF sputtering, investigating the influence of molybdenum addition to gas sensing properties. When working pressure fixed at 7 mtorr, by changing the O2 flow percentage, we tried to find out the SnO2 film which has the best gas sensing ability, thus fix the O2 flow percentage to prepare SnO2：Mo thin films. Changing amount of Mo content by adjusting the Mo sputtering gun power from 0W to 100W. We also investigated the influence of annealing temperature to gas sensing properties.
Films structure are analysed by GIAXRD, morphology and roughness are analysed by FE-SEM and AFM, chemical composition and bonding states are analysed by XPS, gas sensing properties and electrical properties are measured by gas sensing instrument which assembled by our laboratory.
The results indicated that the SnO2 film has the best sensing ability which its O2 flow percentage is 35%, the optimum operation temperature is 450℃ and the optimum annealing temperature is 500℃
The results indicated that addition of molybdenum formed solid solutions, changing the structure of SnO2 matrix. The growth of grains and aggregations was be inhibited. Crystallization and surface roughness（Rrms） decreased when the amount of molybdenum increased.
The results indicated that the SnO2：Mo thin film had the best sensing ability which its Mo sputtering gun power is 60W and the optimum operation temperature is 400℃ and the optimum annealing temperature is 500℃.
The results indicated that instead of SnO2 thin films have the same ability to reducing gases, SnO2：Mo thin films have the selectivity to ethanol vapor.

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