Design of anodically oxidized metal oxide films as a gas sensor material

H-2 sensing properties of an anodically oxidized Nb2O5 film coupled with a noble metal electrode (M/Nb2O5, M: Au, Pt and Pd) have been investigated under various operating conditions. Among the sensors tested, the Nb2O5 film with a Pd electrode, which was prepared by anodic oxidation in an aqueous solution of 0.5 M H2SO4, showed the highest H-2 response, and the logarithmic sensor current under a forward bias was proportional to the logarithmic H2 concentration. The current- voltage characteristics of the Pd/Nb2O5 sensor at 100 degrees C apparently showed a typical rectifying function of a metal-semiconductor junction, which was formed between the Pd electrode and the Nb2O5 thin film, especially in H-2 balanced with dry air. The H-2 response property was improved when it was operated under a forward bias above 150 degrees c. Furthermore, it was confirmed that even at 28 degrees C the Pd/Nb2O5 could respond to H-2 in dry air.