CO(2) Sensing Characteristics of a La(2)O(3)/SnO(2) Stacked Structure with Micromachined Hotplates

Demand for the detection of carbon dioxide (CO [Formula: see text]) is increasing in various fields, including air-quality monitoring, healthcare, and agriculture. On the other hand, smart gas sensors, in which micromachined gas sensors are integrated with driving circuits, are desirable toward the development of the society of the internet of things. In this study, micromachined hotplate-based CO [Formula: see text] sensors were fabricated and their characteristics were investigated. The sensors have La [Formula: see text] O [Formula: see text] /SnO [Formula: see text] stacked layers as a sensing material and Pt interdigitated electrodes. A CO [Formula: see text] response of 2.9 for a CO [Formula: see text] concentration of 1000 ppm was obtained at 350 °C with low power consumption (approximately 17 mW). A relatively large response was obtained compared with previous studies even though a compact sputtered-SnO [Formula: see text] film was used. This high response was speculated to be due to a significant contribution of the resistance component near the electrode. Furthermore, CO [Formula: see text] sensing was successfully performed in the CO [Formula: see text] range of 200–4000 ppm with at least 200-ppm resolution.