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Structural and Chemical Properties of NiOx Thin Films: Oxygen Vacancy Formation in O2 Atmosphere |
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| Authors: | Dr. Raoul Blume Dr. Wolfram Calvet Dr. Aliakbar Ghafari Dr. Thomas Mayer Dr. Axel Knop-Gericke Prof. Dr. Robert Schlögl |
| Affiliation: | 1. Max-Planck-Institut für Chemische Energiekonversion, Postfach 101365, 45413 Mülheim an der Ruhr, Germany;2. Fachbereich 1, Umweltbundesamt, Wörlitzer Platz 1, 06844 Dessau-Roßlar, Germany;3. FG Oberflächenforschung, TU Darmstadt, Otto-Berndt-Str. 3, 64287 Darmstadt, Germany;4. Abt. Anorganische Chemie, Fritz-Haber-Institut der MPG, Faradayweg 4–6, 14195 Berlin, Germany |
| Abstract: | NiOx films on Si(111) were put in contact with oxygen at elevated temperatures. During heating and cooling in oxygen atmosphere Near Ambient Pressure (NAP)-XPS and -XAS and work function (WF) measurements reveal the creation and replenishing of oxygen vacancies in dependence of temperature. Oxygen vacancies manifest themselves as a distinct O1s feature at 528.9 eV on the low binding energy side of the main NiO peak as well as by a distinct deviation of the Ni2p3/2 spectral features from the typical NiO spectra. DFT calculations reveal that the presence of oxygen vacancies leads to a charge redistribution and altered bond lengths of the atoms surrounding the vacancies causing the observed spectral changes. Furthermore, we observed that a broadening of the lowest energy peak in the O K-edge spectra can be attributed to oxygen vacancies. In the presence of oxygen vacancies, the WF is lowered by 0.1 eV. |
| Keywords: | adsorption nickel oxide oxygen vacancy |