TiN in work function type sensors: a stable ammonia sensitive material for room temperature operation with low humidity cross sensitivity

In this work, it was found that exposure of TIN to ammonia (400 ppb-100 ppm) in wet synthetic air at room temperature leads to a reversible decrease of Delta Phi. Then is a change of the work function of -30 meV/decade of increasing ammonia concentration at room temperature. The response time (t(90)) to 1 ppm is less than or equal to 1 min. The sensitivity is a typical room temperature effect as it decreases at higher temperatures up to 100 degrees C. The reaction has a low cross sensitivity to humidity, as - first - the sensitivity to ammonia does not depend on the relative humidity and - second - the work function change due to humidity changes is as low as -2 meV for an increase of 10% in relative humidity. The Diffuse Reflectance Infrared Fourier Transform Spectra (DRIFT-spectra) indicate that the adsorption of ammonia is correlated with a decrease of OH species on the surface. All data are compared to the gas reactions of TiO2. (C) 2000 Elsevier Science S.A. All rights reserved.