Characterization of Amorphous Anodic Nb{sub}2O{sub}5 Nanofilm for Gas Sensing

摘要

Amorphous Nb{sub}2O{sub}5 film of 167nm thickness was fabricated by anodic oxidation of sputter deposited niobium and characterized by TEM, GD-OES and AFM. The electric properties of the anodic films with sputter-deposited circular gold electrodes were studied by AC impedance spectroscopy in ambient gas atmospheres of air, argon, oxygen or hydrogen in the temperature range of 25 - 200°C. The amorphous Nb{sub}2O{sub}5 showed the character of n-type semiconductor. The conductivity of the film, following the Arrhenius behaviour, was independent of the oxygen partial pressure, but was largely dependent on hydrogen partial pressure. The conductivity of the Nb{sub}2O{sub}5 film at room temperature in dry hydrogen was 2.2 orders of magnitude as high as that in air. The enhanced conductivity could be associated with partial reduction of Nb{sup}(5+) in dry hydrogen atmosphere. The addition of water vapor to hydrogen atmosphere reduced conductivity probably due to suppressing the reduction of Nb{sub}2O{sub}5.