title: A multi-technique study of CO2adsorption on Fe3O4magnetite.
abstract: The adsorption of CO2on the Fe3O4(001)-(2 × 2)R45° surface was studied experimentally using temperature programmed desorption (TPD), photoelectron spectroscopies (UPS and XPS), and scanning tunneling microscopy. CO2binds most strongly at defects related to Fe2+, including antiphase domain boundaries in the surface reconstruction and above incorporated Fe interstitials. At higher coverages,CO2adsorbs at fivefold-coordinated Fe3+sites with a binding energy of 0.4 eV. Above a coverage of 4 molecules per (2 × 2)R45° unit cell, further adsorption results in a compression of the first monolayer up to a density approaching that of a CO2ice layer. Surprisingly, desorption of the second monolayer occurs at a lower temperature (≈84 K) than CO2multilayers (≈88 K), suggestive of a metastable phase or diffusion-limited island growth. The paper also discusses design considerations for a vacuum system optimized to study the surface chemistry of metal oxide single crystals, including the calibration and characterisation of a molecular beam source for quantitative TPD measurements.
authors.affiliation: Institute of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10, 1050 Wien, Austria.
authors.forename: Jiri
authors.initials: J
authors.lastname: Pavelec
authors.affiliation: Institute of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10, 1050 Wien, Austria.
authors.forename: Jan
authors.initials: J
authors.lastname: Hulva
authors.affiliation: Institute of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10, 1050 Wien, Austria.
authors.forename: Daniel
authors.initials: D
authors.lastname: Halwidl
authors.affiliation: Institute of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10, 1050 Wien, Austria.
authors.forename: Roland
authors.initials: R
authors.lastname: Bliem
authors.affiliation: Institute of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10, 1050 Wien, Austria.
authors.forename: Oscar
authors.initials: O
authors.lastname: Gamba
authors.affiliation: Institute of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10, 1050 Wien, Austria.
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Jakub
authors.affiliation: Institute of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10, 1050 Wien, Austria.
authors.forename: Florian
authors.initials: F
authors.lastname: Brunbauer
authors.affiliation: Institute of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10, 1050 Wien, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Schmid
authors.affiliation: Institute of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10, 1050 Wien, Austria.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Diebold
authors.affiliation: Institute of Applied Physics, TU Wien, Wiedner Hauptstrasse 8-10, 1050 Wien, Austria.
authors.forename: Gareth S
authors.initials: GS
authors.lastname: Parkinson