Highly sensitive NO2 gas sensors based on heterostructured p-rGO/n-Ga2O3 nanorods

In this study, using a sensing membrane composed of p-type reduced graphene oxide (rGO)-decorated hydrothermally synthesized n-type gallium oxide (Ga₂O₃) nanorods, nitrogen dioxide (NO₂) gas sensors were successfully fabricated. The characteristics of the rGO-decorated Ga₂O₃ nanorods were analyzed by X-ray photoelectron spectroscopy (XPS). The experimental results indicated that the rGO decoration on the surface of the Ga₂O₃ nanorods increased the amount of gas adsorption sites and oxygen vacancies, thereby enhancing electrical conductivity. Consequently, compared to NO₂ gas sensors utilizing only Ga₂O₃ nanorods, the NO₂ gas sensors using rGO-decorated Ga₂O₃ nanorod sensing membrane exhibited lower resistance, reduced activation energy, and higher response. Optimal response, reaching 51.14, was achieved by decorating with 15 mg of rGO. Additionally, the response and recovery times of the NO₂ gas sensors were shortened with an increase in the amount of rGO decoration on the Ga₂O₃ nanorods. This improvement could be attributed to the trend of lower activation energy associated with an increased amount of rGO decoration. This study demonstrates the efficacy of rGO decoration in improving the performance of Ga₂O₃ nanorod-based NO₂ gas sensors.