Nano-grained thin-film indium tin oxide gas sensors for H2 detection

Nano-grained indium tin oxide (ITO) thin films catalyzed 0.5 wt.% Pd were deposited on the alumina substrate at ambient temperature or 300 °C by using an rf magnetron sputtering system and then annealed at 650 °C for 1 or 4 h in air. The crystallinity and microstructure of the annealed films were analyzed. The effects of their microstructure (nano-grain) and ITO composition on H2 gas-sensing properties were systematically investigated. As the results of XRD and Field Emission Scanning Electron Microscope (FESEM) analysis, polycrystalline thin films with 10-35 nm in grain size were obtained. The ITO (In2O3:SnO2 = 20:80) sensors showed high H2 sensitivity, Rgas/Rair = 0.008 at 1000 ppm.