| Summary: | 碩士 === 崑山科技大學 === 電機工程研究所 === 106 === In this study, a tungsten film was coated on a silicon substrate plated with an electrode by direct current sputtering, and then the tungsten film was oxidized by a thermal oxidation method to prepare a WO3 hydrogen sensor. Different structures of tungsten oxide films are obtained by changing the growth temperature and pressure in the thermal oxidation process, it applied for hydrogen sensors to obtain at a different measuring temperature for investigated on better sensing characteristics. The X-ray diffraction (XRD) was used to analyze the structure of the film and the field emission scanning electron microscope (FE-SEM) was to observe the surface morphology. PL spectral analysis was used to measure the properties of light emission. The gas sensing system was used to detect hydrogen sensing properties.
According to the experimental results, the oxidation temperature has a great influence on the morphology of WO3 nano-rods. The tungsten oxide film was grown on different temperature. The film grown at 550 °C has no strong oxide peak are found in XRD diffraction pattern. The film shows only a small amount of tungsten oxide on the surface. When the growth temperature rises to 650-750 ° C, there are obvious diffraction peaks are found. A large number of nano-rods are also found in this growth condition. The structure of nano-rods is not obvious, when the temperature is up to 850°C.
The sensing ability can be observed at 250°C in 1% hydrogen concentration. The sensitivity reaches about 1.2 at oxidation temperature of 750 ° C. The sensitivity will increase with the growth temperature rises. When the temperature rises to 850 °C, the sensitivity will decrease, that indicate the nano-rods structure has a very significant influence for the sensing properties. The sensing signal can’t be obtained when the sensing is measured at room temperature and 150 °C. In our experiments, the best sensing result is at the temperature of 250 ° C. When the sensing temperature rises to 350 ° C, the sensitivity decreases was found.
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