Low-Voltage-Driven SnO 2 -Based H 2 S Microsensor with Optimized Micro-Heater for Portable Gas Sensor Applications.

To realize portable gas sensor applications, it is necessary to develop hydrogen sulfide (H 2 S) microsensors capable of operating at lower voltages with high response, good selectivity and stability, and fast response and recovery times. A gas sensor with a high operating voltage (>5 V) is not suitable for portable applications because it demands additional circuitry, such as a charge pump circuit (supply voltage of common circuits is approximately 1.8-5 V). Among H 2 S microsensor components, that is, the substrate, sensing area, electrode, and micro-heater, the proper design of the micro-heater is particularly important, owing to the role of thermal energy in ensuring the efficient detection of H 2 S. This study proposes and develops tin (IV)-oxide (SnO 2 )-based H 2 S microsensors with different geometrically designed embedded micro-heaters. The proposed micro-heaters affect the operating temperature of the H 2 S sensors, and the micro-heater with a rectangular mesh pattern exhibits superior heating performance at a relatively low operating voltage (3-4 V) compared to those with line (5-7 V) and rectangular patterns (3-5 V). Moreover, utilizing a micro-heater with a rectangular mesh pattern, the fabricated SnO 2 -based H 2 S microsensor was driven at a low operating voltage and offered good detection capability at a low H 2 S concentration (0-10 ppm), with a quick response (<51 s) and recovery time (<101 s).