H2 sensing properties and mechanism of anodically oxidized TiO2 film contacted with Pd electrode

TiO2 thin films have been prepared by anodic oxidation of Ti plates at different temperatures, and H-2 sensing properties of the obtained TiO2 thin film sensors equipped with a Pt and Ti electrode have been investigated both in air and N-2 under forward and reverse bias conditions. The TiO2 thin film prepared by the anodic oxidation at 20 degreesC had a large number of sub-micron pores, and exhibited the highest sensitivity and reversible response to H-2 both in air and N-2 under forward and reverse bias conditions. The current-voltage (I-V) characteristic of the sensor was roughly Ohmic in 0.8% H-2 balanced with N-2, while it was non-Ohmic in other environments studied. In addition, the change in the Schottky barrier height at the interface between Pd and TiO2 induced by H-2 was larger in N-2 than in air, and also under reverse bias than forward bias conditions. The reversible and concentration-dependent H-2 sensitivity of the sensor in N-2 was suggested to arise mainly from the change in the Schottky barrier height induced by dissolution of H atoms in the Pd bulk. (C) 2003 Elsevier Science B.V. All rights reserved.