Fast response hydrogen microsensor based on semiconductor niobium-oxide nanostructures via smart anodizing of Al/Nb metal layers

Abstract

Nanostructured niobium oxide semiconductor is gaining increasing attention as electro-optic and gas sensing material. However, the preparation of stable niobium oxide nanofilm with reproducible morphology and behaviour remains a challenge. Here we describe a rapid and well-controlled approach to synthesize a niobium oxide film with the columnlike nanostructured morphology via anodic processing of Al/Nb metal layers sputtered onto an oxide-coated Si wafer. The film is developed due to the growth of a nanoporous anodic alumina layer followed by pore-directed oxidation of the Nb underlayer. The post-anodizing treatment results in the controlled formation of Nb2O5 crystal phase, which causes the transformation from dielectric to n-type semiconductor behavior of the film. A laboratory gas sensor fabricated by uniting the anodizing approach developed here with standard micromachining technologies shows superior characteristics for hydrogen gas detection, the response-recovery time being among best ever reportedNanostructured niobium oxide semiconductor is gaining increasing attention as electro-optic and gas sensing material. However, the preparation of stable niobium oxide nanofilm with reproducible morphology and behaviour remains a challenge. Here we describe a rapid and well-controlled approach to synthesize a niobium oxide film with the columnlike nanostructured morphology via anodic processing of Al/Nb metal layers sputtered onto an oxide-coated Si wafer. The film is developed due to the growth of a nanoporous anodic alumina layer followed by pore-directed oxidation of the Nb underlayer. The post-anodizing treatment results in the controlled formation of Nb2O5 crystal phase, which causes the transformation from dielectric to n-type semiconductor behavior of the film. A laboratory gas sensor fabricated by uniting the anodizing approach developed here with standard micromachining technologies shows superior characteristics for hydrogen gas detection, the response-recovery time being among best ever reported