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Atomic structure of Cu2O(111)
KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.ORCID iD: 0000-0001-7409-575X
2009 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 603, no 2, 257-264 p.Article in journal (Refereed) Published
Abstract [en]

Low-energy electron diffraction and scanning tunneling microscopy have been used to probe the surface atomic structure Of Cu2O(111) after various sample preparations. Annealing in oxygen gives a stoichiometric (1 x 1) oxygen terminated surface and further annealing in ultra-high vacuum results in a clear (root 3 x root 3)R30 degrees reconstruction and surface faceting. Tunneling from filled states in the reconstructed surface reveals a hexagonal pattern of large protrusions, which show an internal structure. The reconstruction is believed to be due to one-third of a monolayer of ordered oxygen vacancies. At areas on the surface where the large features are missing, another smaller type of protrusions is visible, which is associated with the ideal (1 x 1) surface. The relative position of the two types of features gives two possible models of the (111) surface. In the first model, the (1 x 1) surface is the ideal bulk terminated surface and coordinatively unsaturated oxygen ions are missing in the reconstructed surface. The second model agrees with the first model with the exception that coordinatively unsaturated copper ions in the outmost copper layer are missing in both the (1 x 1) and the reconstructed surface. The latter model is supported by previous surface free energy calculations. Since the undercoordinated copper ions have been suggested to be the catalytic active sites Of Cu2O(111), the presence or absence of these cations could be of great importance for the fundamental understanding of the surface reactivity Of Cu2O and of copper-based catalysts.

Place, publisher, year, edition, pages
2009. Vol. 603, no 2, 257-264 p.
Keyword [en]
Catalysis, Copper oxides, Low-energy electron diffraction (LEED), Scanning tunneling microscopy, Scanning tunneling spectroscopies, Single crystal surfaces, Surface defects, Surface structure, scanning-tunneling-microscopy, energy synchrotron-radiation, temperature steam conversion, plasma-chemical preparation, density-functional theory, closed-shell interactions, electronic-structure, nanostructured catalysts, polar covalences, carbon-monoxide
URN: urn:nbn:se:kth:diva-18173DOI: 10.1016/j.susc.2008.10.048ISI: 000263384500003ScopusID: 2-s2.0-58249115242OAI: diva2:336219
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-05-16Bibliographically approved
In thesis
1. Surface Reactivity and Electronic Structure of Metal Oxides
Open this publication in new window or tab >>Surface Reactivity and Electronic Structure of Metal Oxides
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The foci of this thesis are the metal oxides Cu2O, ZnO and Fe3O4 and their interaction with water and sulfur dioxide (SO2). The intention is to study SO2-induced atmospheric corrosion on a molecular level. All studies are based on photoelectron spectroscopy (PES) and scanning tunneling microscopy (STM) measurements. The band structure of Cu2O in the Γ-M direction has been probed by angle-resolved PES (ARPES). It reveals a more detailed picture of the bulk band structure than earlier data and gives the first experimental evidence of a dispersive hybridized Cu 3d-Cu 4s state. The experimental data is compared to band structure calculations. The structure of clean metal oxide surfaces and impact of sample preparation have been studied. Oxygen vacancies can form a (√3x√3)R30° reconstruction on Cu2O(111). Oxygen atoms adjacent to copper vacancies, steps or kinks are shown to be adsorption sites for both water and SO2. Annealing temperature influences the defect density and hydrogen content in ZnO, which can have large impact on the surface properties of ZnO(0001). Water is shown to adsorb dissociatively on ZnO(0001) and partly dissociatively on Cu2O(111). The dissociation occurs at undercoordinated oxygen sites on both surfaces. Water stays adsorbed on ZnO(0001) at room temperature but on Cu2O(111), all water has desorbed at 210 K. SO2 interacts with one or two undercoordinated O-sites on all studied oxide surfaces forming SO3 or SO4 species respectively. SO4 on Fe3O4(100) follows the (√2x√2)R45° reconstruction. On Cu2O(111) and ZnO(0001), SO2 adsorbs on defect sites. An SO3 to SO4 transition is observed on Cu2O(111) when heating an SO3 adsorbate layer from 150 K to 280K. Coadsorption of water and SO2 on ZnO(0001) and Fe3O4(100) has been studied briefly. Water blocks SO2 adsorption sites on ZnO(0001). On Fe3O4(100) and on one type of reduced ZnO(0001) sample, SO2 dissociation to atomic sulfur or sulfide occurs to a higher extent on water exposed surfaces than on clean surfaces. Water thus appears to increase the charge density on some surfaces. Further studies are needed to reveal the cause of this unexpected effect.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. xiv, 58 p.
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2011:07
oxides, surfaces, defects, cuprous oxide, zinc oxide, magnetite, water, OH, sulfur dioxide, photoelectron spectroscopy, scanning tunneling microscopy
National Category
Other Engineering and Technologies not elsewhere specified
urn:nbn:se:kth:diva-33667 (URN)978-91-7415-995-0 (ISBN)
Public defence
2011-05-30, Electrum, C2, Isafjordsgatan 26, Kista, 10:00 (English)

QC 20110516

Available from: 2011-05-16 Created: 2011-05-13 Last updated: 2012-10-30Bibliographically approved

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Önsten, AnneliGöthelid, MatsKarlsson, Ulf O.
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