Morphological engineering for constructing GaN-decorated SnO2 nanopolygons with enhanced sensitivity and selectivity towards NO2 gas

Abstract

In this study, we synthesized SnO₂ nanowires (NWs) using a vapor–liquid–solid growth mechanism. Prior to the GaN-deposition on SnO₂ NWs, high-temperature etching using a strong HCl acid changed the SnO₂ morphology to nanopolygons (NPGs). GaN nanoparticles (NPs) were then decorated onto the SnO₂ NPGs using a self-designed vertical hydride vapor-phase epitaxy technique for 0–30 s. The characterization studies revealed the formation of GaN-decorated SnO₂ NPGs. Subsequently, gas sensors were fabricated. At 300 °C, pristine SnO₂ NW sensor revealed a response of 56.1–10 ppm NO₂ gas, whereas all GaN-decorated SnO₂ NPG gas sensors achieved higher detection response. Moreover, the sensor with the GaN deposition time of 20 s exhibited the highest response of 111.1–10 ppm NO₂ gas. The optimized sensor exhibited high selectivity, good repeatability, and long-term stability. Enhanced NO₂ sensing performance of optimized sensor was related to the high specific surface area (29.7 m²/g), formation of n–n GaN/SnO₂ heterojunctions and sufficient GaN decoration time, where sufficient amounts of GaN NPs were deposited on SnO₂ NPGs. Therefore, this study demonstrated the promising sensing capability of GaN-decorated SnO₂ NPGs, which can be regarded as a novel sensing system to realize highly sensitive and selective NO₂ gas sensors.