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 ΔΦ. There is a change of the work function of −30 meV/decade of increasing ammonia concentration at room temperature. The response time (t90) to 1 ppm is ≤1 min. The sensitivity is a typical room temperature effect as it decreases at higher temperatures up to 100°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.