| 摘要 |
PROBLEM TO BE SOLVED: To bring the resistance of a metal oxide semiconductor closer when CO and an inflammable gas are detected and to reduce temperature dependency when the CO is detected by composing an inner layer where Sb is added to SnO2 with the metal oxide semiconductor that is covered with an outer layer where no Sb is added to SnO2. SOLUTION: In a gas sensor 2, an inner layer 6 where Sb is added to SnO2 is provided on an insulation substrate 4 such as alumina, covering is made by an outer layer 8 using SnO2 where Sb is not added, thus composing a metal oxide semiconductor. By adding Sb to the inner layer 6, temperature dependency when detecting CO can be reduced. Also, by adding Sb only to the inner layer 6, sensitivity to an in-flammable gas (methane) cannot be reduced. More specifically, a pair of electrodes 10 and 12 is connected to the inner layer 6, the temperature of the metal oxide semiconductor is periodically changed between high- temperature and low-temperature regions by a heater 14 that is provided on the reverse side of the insulation substrate 4, thus detecting methane and CO from resistance values at the high-temperature and low-temperature regions, respectively, and hence bringing the resistance values in both the detection closer.
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