Hydrogen gas sensing properties of nanoporous Al-doped titania

Abstract

Nanoporous aluminum doped titanium (TiAl) oxide thin film sensor materials with an Al concentration of 9-10 at.% were produced on alumina substrates and their hydrogen (H2) sensing behaviors were investigated. The well-adherent and dense metallic TiAl thin films with equiaxed structure were deposited on alumina substrates using cathodic arc physical vapor deposition (CAPVD) method and the nanopores were grown on the TiAl thin films by anodic oxidation in ammonium fluoride (NH4F) containing ethylene glycol (EG) electrolyte. With the deposition method utilized, it became possible to anodize the films without spalling and defects. The metallic film on alumina was totally anodized in order to eliminate short-circuit problems between the metallic layer below the oxide and Pt pads used for resistance measurements. The amorphous nanoporous structures were converted into anatase by heat treatment at 480 °C for 3 h and the fabrication of sensor was completed by depositing Pt contact pads on the surface of nanopores using magnetron sputtering technique. The hydrogen sensing performance of thin film nanoporous TiAl oxide sensor was studied in the range of 50-2500 ppm hydrogen at different temperatures (25-350 °C). The sensor characteristics in terms of sensitivity, response, recovery and stability were examined in detailed analysis and a possible hydrogen detection mechanism was proposed. The nanoporous TiAl oxide sensor exhibited promising sensing performance towards H2 gas concentrations and quick response and recovery behavior with high stability. © 2014 Elsevier B.V.