A highly stable SiC based microhotplate NO2 gas-sensor

A new heated microgas-sensor with only 80 μm×80 μm active heater area and excellent long-term stability is presented. Using a previously presented SiC based microhotplate and depositing an In2O3 thin film layer on top of the interdigital electrode (IDE) structure an NO2 sensor for the MAK-range (German maximum workplace concentration limit: 5 ppm) was fabricated. The microhotplate allows a maximum operating temperature of up to 650°C, which is limited only by the IDE metallisation stability. When using In2O3 layers for NO2 detection, the hotplates’ low operating power of 20 mW allows the continuous operation at operating temperature with an AAA battery cell for 75 h. More than 20,000 work cycles of 1 min could be realised before device failure leading to a life time of over half a year when sampling the ambient gas every 10 min.