Surface properties of indium oxide and its interaction with ozone for the use as gas sensor

cost and low energy consumption environmental sensors, e.g. for the detection of ozone. We have examined the surface properties of indium oxide films prepared by metal organic chemical vapour deposition using X-ray and ultraviolet photoelectron spectroscopy (XPS,UPS). The influence of the growth temperature on stoichiometry as well as the surface electronic structure is presented. Especially for low temperature (200 C) grown samples strong emission from an up to date unidentified state below the valence band maximum is observed. In order to identify the photoreduction and oxidation mechanisms related to the ozone sensor principle, we have investigated the interaction of indium oxide with ozone and UV radiation. For the interaction with ozone, two adsorbate related states at 6.1 eV and 11.3 eV appear in the valence band together with an increase in the work function and a change in the surface band bending. A model will be proposed to explain the interaction of ozone with the indium oxide surface with respect to the observed drastic changes in resistivity of the samples