Synthesis and CO gas sensing properties of surface-nitridated Ga2O3 nanowires

Abstract

Ga₂O₃ based gas sensors have limited use at a temperature lower than 400 °C because of their poor performances at low temperatures. Efforts to further improve their performances at room temperature are necessary. This study examines the sensing properties of surface-nitridated Ga₂O₃ nanowires toward CO gas. Surface-nitridated Ga₂O₃ nanowires were fabricated by thermal evaporation of GaN powders followed by thermal nitridation in an NH₃ atmosphere. Scanning electron microscopy and transmission electron microscopy showed that the GaN shell layer in a typical surface-nitridated nanowire had a thickness of ∼21 nm and excellent shell layer thickness uniformity. Multiple networked surface-nitridated Ga₂O₃ nanowire sensors showed responses of 160–363% to CO concentrations of 10–200 ppm at 150 °C. These responses were 1.6–3.1 fold stronger than those of pristine Ga₂O₃ nanowire sensors at the same CO concentrations and stronger than those of many pristine metal oxide nanostructures and Ga₂O₃/metal oxide core–shell nanowires at similar temperatures. The results showed that the sensitivity of Ga₂O₃ nanowires could be enhanced by simple ammoniation treatment. The enhanced response of the surface-nitridated Ga₂O₃ nanowires to CO gas can be explained based on a potential barrier carrier transport mechanism combined with a surface depletion mechanism and excellent shell layer uniformity.