| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 1998: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1997: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
ITO is used as transparent conductive film for liquid crystal display, and it is possible to use as gas sensor for NO_2, which causes environmental pollution. The sensing properties of ITO films prepared by sputtering and electron shower method were investigated in this study. When NO_2 gas was flown steadily in a measurement tube, the sensitivity behavior of the sensor film prepared by the electron shower was more excellent than that prepared by sputtering. This was due to the rough surface, which was obtained by the growth of VLS (vapor-liquid-solid) whiskers along the substrate. In general, whiskers grew perpendicularly to the substrate. The ITO whiskers, however, grew along the substrate. We found the factor to determine the growth direction of the whiskers.
It has been studied that the NO_x concentration in a tunnel was decreased by photocatalysis. In this study, NO_x was decomposed by ZnO photocatalyst prepared by electroplating. The low-priced and simple ITO-film gas sensor was used for the monitoring of the NO_2 gas decomposition. When the flow of the gas was stopped and NO_2 gas was sealed in the tube, many sensors showed the NO_2 concentration was decreased without leakage and they could not be used as a sensor. Especially, when the temperature of the sensor or the concentration of NO_2 was high, this phenomenon appeared remarkably. When the measurement was repeated, the leakage phenomenon did not occur, and it was used as sensor. This phenomenon was explained by the consideration of the existence of stable and unstable NO_2 adsorption sites. When the sensor area was too small, the leakage phenomenon appeared. When the area was too large, the response time became long. It was found that there was a proper sensor area to show a high response for a concentration of NO_2
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