Polycrystalline Dy-doped SrTiO3 thin films deposited using pulsed laser deposition (PLD) on CeO2 buffered yttria-stabilized zirconia (YSZ) single crystal substrate showed oxygen sensing characteristics operated at room temperature. Oxygen gas sensing characteristics depends on the amount of Dy-doping, and 1.5 mol% Dy-doping was most effective. The oxygen gas sensing characteristics was closely related to the leakage current measured for polycrystalline PLD Dy-doped SrTiO3 thin film deposited on
ZnIn2O4/YSZ/Si(001) substrate. The suppression of leakage current by Dy-doping suggests that Dy3+ is substituted in to Ti4+ site and acted as an acceptor. Further doping of Dy3+ brought the increase of leakage current and lowered oxygen gas sensitivity.