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Interaction of indium oxide nanoparticle film surfaces with ozone, oxygen and water

: Himmerlich, M.; Eisenhardt, A.; Berthold, T.; Wang, C.Y.; Cimalla, V.; Ambacher, O.; Krischok, S.


Physica status solidi. A 213 (2016), Nr.3, S.831-838
ISSN: 0031-8965
ISSN: 1862-6300
ISSN: 1521-396X
ISSN: 1862-6319
Deutsche Forschungsgemeinschaft DFG
SPP 1386; KR 2228/6
Fraunhofer IAF ()
indium oxide; photoelectron spectroscopy; adsorption; electronic property; gas sensor

The interaction of defect-rich nanocrystalline indium oxide films, which have previously shown to exhibit excellent ozone sensing properties, with O-3, O-2, and H2O molecules is investigated using ultra-violet and X-ray photoelectron spectroscopy. The investigated samples are grown by metalorganic chemical vapor deposition at low temperatures resulting in high oxygen deficiency and high defect density. The ozone-induced surface oxidation and UV-induced photoreduction mechanisms of the ozone sensor active material are evaluated with respect to surface stoichiometry and electronic properties including adsorbate features, band bending and surface dipole formation. A strong interaction with ozone and water is found, whereas the interaction with O-2 is relatively weak. In all cases the interaction results in the same negatively charged oxygen adsorbate species. which can either be removed by UV light or by annealing resulting in the capability of these films to be used in reversible adsorption induced oxidation and UV/thermal reduction cycles.