Oxidizing Gas Sensor With Low Concentration Using Complex Impedance

In recent years, because of increased carbon dioxide emissions problem, the air pollution has been attracting attention. For example, the exhaust fumes produce nitrogen oxide and sulfur oxide. Therefore, these gases should be detected and measured. In this paper, we propose a novel moisture-insensitive sensor consisting of a comb-shaped electrode on a Si substrate. We also suggest a new measurement method, using complex impedances, for distinguishing between NO2 and SO2 at low concentrations. It is shown that propose oxidizing-gas sensor, fabricated on a Si substrate, is moisture-insensitive for humidity of 40% to 80%. Furthermore, we determine that it is possible to measure mixed gases in the range of 0.1-0.9 ppm for nitrogen dioxide and 0.6-1.4 ppm for sulfur dioxide owing to the difference in the complex-impedance change pattern.