H2 sensing perfortnance of anodically oxidized TiO2 thin films equipped with Pd electrode

Hydrogen sensing properties of TiO2 thin films prepared by different methods and equipped with different kinds of metal electrodes have been tested. The most developed submicron-sized pore structure was found in the TiO2 thin film prepared by anodic oxidation of a Ti metal plate in a H2SO4 solution at 20 degrees C. The sensor fabricated with this film and a Pd electrode showed the highest H-2 response among the sensors fabricated with different TiO2 films and electrode metals at elevated temperatures. This TiO2 thin film sensor equipped with a Pd electrode can be classified into a diode-type sensor from the change in I-V curve induced by H-2, and is characterized with reversible H, response even in N-2 atmosphere. The H-2 sensing mechanism is suggested to arise from dissolution of H atoms into the Pd electrode and a decrease in Schottky barrier height at the interface between the Pd electrode and the TiO2 thin film. Although the present sensor showed pretreatment-dependent H-2 response properties, modification of the Pd electrode was found to be effective for reducing or improving the pretreatment-dependent H-2 response properties. (c) 2006 Elsevier B.V. All rights reserved.