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.