Enhanced CO gas sensing properties of multiple networked Ga2O3-core/TiO2-shell nanorod gas sensors

초록

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 600–1000 oC, which limits their practical use. This study examined the effect of the encapsulation of Ga2O3 nanorods with TiO2 on the CO gas sensing properties. Ga2O3-core/TiO2-shell nanorods were fabricated by a two step process comprising the thermal evaporation of TiO2 powders and metal organic chemical deposition of TiO2. Multiple networked Ga2O3-core/TiO2-shell nanorod sensors showed the sensitivities of 748, 1677, 3277 and 2734% at CO concentrations of 10, 50, 100 and 200 ppm, respectively, at 300 oC. These sensitivity values are 18, 37, 69, and 35 times larger than those of bare-Ga2O3 nanorod sensors at CO concentrations of 10, 50, 100 and 200 ppm, respectively. The sensitivity of the core-shell nanorods to CO gas were superior to those of other material nanosensors reported previously. The substantial improvement in the sensitivity of Ga2O3 nanorods to CO gas by the encapsulation by TiO2 can be accounted for based on the space-charge model. The Ga2O3-TiO2 heterojunction acts as a lever in electron transfer from which the electron transfer is facilitated or restrained, resulting in an enhanced sensing property of the core-shell nanorod sensor.