Molybdenum Oxide Nanorods Based Thin Films: Effect of Electrode Metallization on Hydrogen and Ethanol Sensing

Nanostructured molybdenum oxide (MoO3) gas sensitive layers were deposited on Au and Pt inter-digitated electrodes (IDE) integrated to alumina substrates by RF magnetron sputtering and controlled post deposition annealing. Sensitivity test measurements towards hydrogen and ethanol vapour under non-humid and humid ambience at isothermal (200°C a nd 300°C) operation are presented. Extremely different response behaviour to the analytes depending on operating temperature, background humidity and electrode material was observed. The humid ambience does not significantly change the sensitivity to H2 whereas it diminishes the sensitivity to ethanol. Non-dissociative and dissociative adsorption of analytes on the sensing layer and diffusion effects due to different layer morphologies were taken into account in order to interpret the diverse sensing behaviour. Influence of the electrode material on the sensor performance of the MoO3 layers towards H2 and ethanol is demonstrated. The catalytic effect of the Pt-IDE on the sensitivity is identified at higher temperature (300°C). Key words: MoO3 nanorods, hydrogen and ethanol sensing, humidity and electrode materia