Ozone gas sensors with high sensitivity using Zn2In2O5–MgIn2O4 multicomponent oxide thin films

High-sensitivity ozone (O3) gas sensors have been newly developed using a multicomponent oxide thin film such as Zn2In2O5–MgIn2O4. The Zn2In2O5–MgIn2O4 multicomponent oxide thin-film gas sensors used in this work exhibited an increase in resistance with exposure to O3 gas; the sensing properties were strongly dependent on the chemical composition of the multicomponent oxide films used as well as the operating temperature. The highest sensitivity for O3 gas was obtained in sensors using a Zn2In2O5–MgIn2O4 thin film prepared with a Zn2In2O5 content of 20 mol%. When operated at 275°C in air, they were able to detect O3 gas at a minimum concentration of 0.4 ppm. The sensitivity of the (Zn2In2O5)0.2–(MgIn2O4)0.8 thin-film gas sensor was increased by a factor of approximately 10 when exposed to 5 ppm O3 gas with a concentration. An increase of resistivity in Zn2In2O5–MgIn2O4 thin-film sensors with exposure to O3 gas resulted from a simultaneous decrease of both carrier concentration and Hall mobility. The increase in resistivity is attributed to the trapping of free electrons resulting from O3 being adsorbed on grain boundaries and/or the film surface.