Ozone gas sensors with high sensitivity using Zn 2In 2O 5–MgIn 2O 4 multicomponent oxide thin films

Abstract

High-sensitivity ozone (O 3) gas sensors have been newly developed using a multicomponent oxide thin film such as Zn 2In 2O 5–MgIn 2O 4. The Zn 2In 2O 5–MgIn 2O 4 multicomponent oxide thin-film gas sensors used in this work exhibited an increase in resistance with exposure to O 3 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 O 3 gas was obtained in sensors using a Zn 2In 2O 5–MgIn 2O 4 thin film prepared with a Zn 2In 2O 5 content of 20 mol%. When operated at 275°C in air, they were able to detect O 3 gas at a minimum concentration of 0.4 ppm. The sensitivity of the (Zn 2In 2O 5) 0.2–(MgIn 2O 4) 0.8 thin-film gas sensor was increased by a factor of approximately 10 when exposed to 5 ppm O 3 gas with a concentration. An increase of resistivity in Zn 2In 2O 5–MgIn 2O 4 thin-film sensors with exposure to O 3 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 O 3 being adsorbed on grain boundaries and/or the film surface.