| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 97 === 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.
|
|---|
