Hydrogen and ethanol sensing properties of molybdenum oxide nanorods based thin films: Effect of electrode metallization and humid ambience

Nanostructured molybdenum oxide (MoO3) gas sensitive layers were prepared via RF magnetron sputtering and controlled post deposition annealing on Au and Pt inter-digitated electrodes (IDE), which are integrated onto alumina substrates. Sensitivity test measurements towards hydrogen and ethanol vapour at different concentrations in synthetic air under non-humid and humid ambience at isothermal (200 °C and 300 °C) conditions are presented. Extremely different response behaviour to the analytes depending on morphology of the sensing layer, operating temperature, background humidity and electrode material was observed. The humid ambience does not significantly change the sensitivity to H2, however, it drastically diminishes the sensitivity to ethanol. At higher temperature (300 °C), influence of electrode material (catalytic effect of Pt from the Pt-IDE) on the gas sensing performance of MoO3 layer is identified. Non-dissociative and dissociative adsorption of analytes on the sensing layer, reaction of the adsorbed analyte species with lattice oxygen and diffusion effects due to different layer morphologies were taken into account in order to account the diverse sensing behaviour.