Ga2O3-based gas sensors show very poor performance at room temperature despite being able to detect a range of gases efficiently at high temperatures of 600-1,000 oC, which limits their practical use. Ga2O3-core/ZnO-shell nanowires were synthesized by the thermal evaporation of GaN powders followed by the atomic layer deposition of ZnO and then multiple networked Ga2O3-core/ZnO-shell nanowire gas sensors were fabricated. The morphology, crystal structure, and sensing properties of pristine Ga2O3 nanowires and Ga2O3-core/ZnO-shell nanowires to NO2 gas at room temperature under ultraviolet (UV) illumination were examined. Pristine Ga2O3 nanowires and Ga2O3-core/ZnO-shell nanowires showed responses ranging from ~ 249 to ~ 703% and from ~ 557 to ~ 2,110%, respectively, to 1-5 ppm NO2 under UV (365 nm, 1.2 mW/cm2) illumination, corresponding to 2.2-3.0 fold increases, by encapsulation of ZnO nanowires with ZnO. On the other hand, the responses of both types of nanowires were almost 0 at room temperature in the NO2 concentration range of 1-5 ppm. The underlying mechanism for the enhanced gas sensing properties of Ga2O3-core/ZnO-shell nanowires toward NO2 gas under UV illumination is discussed in detail.

Keywords: Ga2O3, Core-shell nanowire, Gas sensor, NO2, UV.