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).