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  • 1.
    Alfredsson, Ylfi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Åhlund, John
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Nilson, Katharina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Kjeldgaard, Lisbeth
    O´Shea, J. N.
    Theobald, J.
    Bao, Zhuo
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Phase and molecular orientation in H2Pc on conducting glass: characterization of two deposition methods2005In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 493, no 1-2, p. 13-19Article in journal (Refereed)
    Abstract [en]

    In this study, metal-free phthalocyanine has been deposited on a conducting glass surface by two methods: by spreading the molecular powder directly on the substrate in air and by vapor sublimation under ultra-high vacuum conditions (evaporation). The films have been characterized by means of core level X-ray Photoemission Spectroscopy, X-ray Absorption Spectroscopy (XAS) and Ultra Violet and Visible absorption spectroscopy (UV-Vis). Our results show that the two deposition methods produce molecular overlayers in different polymorphic phases; the UV-Vis measurements indicate that the film obtained by powder deposition is of x-phase type whereas sublimation leads to an α-polymorph structure. The XAS results show that in the powder deposited film the molecules are mainly oriented parallel to the surface. This is opposite to the case of the vapor deposited film, where the molecules mainly are oriented orthogonal to the surface.

  • 2.
    Alfredsson, Ylvi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Brena, Barbara
    Nilson, Katharina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Åhlund, John
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Kjeldgaard, Lisbeth
    Nyberg, Mats
    Luo, Yi
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Electronic structure of a vapor-deposited metal-free phthalocyanine thin film2005In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 122, no 21, p. 214723-Article in journal (Refereed)
    Abstract [en]

    The electronic structure of a vapor-sublimated thin film of metal-free phthalocyanine(H2Pc) is studied experimentally and theoretically. An atom-specific picture of the occupied and unoccupied electronic states is obtained using x-ray-absorption spectroscopy (XAS), core- and valence-level x-ray photoelectron spectroscopy (XPS), and density-functional theory (DFT) calculations. The DFT calculations allow for an identification of the contributions from individual nitrogen atoms to the experimental N1sXAS and valence XPS spectra. This comprehensive study of metal-free phthalocyanine is relevant for the application of such molecules in molecular electronics and provides a solid foundation for identifying modifications in the electronic structure induced by various substituent groups.

  • 3.
    Alfredsson, Ylvi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Åhlund, John
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Nilson, Katharina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Kjeldgaard, Lisbeth
    O'Shea, James
    Theobald, J
    Bao, Zhuo
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Phase and molecular orientation in metal-free phthalocyanine films on conducting glass: Characterization of two deposition methods2005In: Thin Solid Films, Vol. 493, no 1-2, p. 13-19Article in journal (Refereed)
  • 4. Amft, M.
    et al.
    Walle, L. E.
    Ragazzon, Davide
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Borg, A.
    Uvdal, P.
    Skorodumova, Natalia V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    A Molecular Mechanism for the Water-Hydroxyl Balance during Wetting of TiO22013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 33, p. 17078-17083Article in journal (Refereed)
    Abstract [en]

    We show that the formation of the wetting layer and the experimentally observed continuous shift of the H2O-OH balance toward molecular water at increasing coverage on a TiO2(110) surface can be rationalized on a molecular level. The mechanism is based on the initial formation of stable hydroxyl pairs, a repulsive interaction between these pairs, and an attractive interaction with respect to water molecules. The experimental data are obtained by synchrotron radiation photoelectron spectroscopy and interpreted with the aid of density functional theory calculations and Monte Carlo simulations.

  • 5. Blomquist, J.
    et al.
    Walle, L. E.
    Uvdal, P.
    Borg, A.
    Sandell, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Water Dissociation on Single Crystalline Anatase TiO2(001) Studied by Photoelectron Spectroscopy2008In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 42, p. 16616-16621Article in journal (Refereed)
    Abstract [en]

    The adsorption of water on the anatase TiO2(001)-(4 x 1) surface is studied using synchrotron radiation-excited core level photoelectron spectroscopy. The coverage-dependent adsorption of water at low temperature is monitored and compared to the sequence obtained after heating of a water multilayer. Two adsorption phases of submonolayer coverage can be defined: Phase 1 consists only of dissociated water, observed as OH-groups. This phase is found at low coverage at low temperature (190 K) and is the only state of adsorbed water above similar to 230 K. The saturation coverage of phase 1 is consistent with dissociation on the 4-fold-coordinated Ti ridge atoms of the (4 x 1) surface reconstruction. Phase 2 is found at higher coverage, reached at lower temperature. It consists of a mixture of dissociated and molecular water with a ratio of 1:1 at 170 K. The molecular water is found to bond to the hydroxyl groups. The hydroxyl coverage of phase 2 is approximately 2 times that of phase 1. The results suggest that the OH and H2O species of phase 2 are confined to the ridges of the surface.

  • 6. Dorkhan, Marjan
    et al.
    Hall, Jan
    Uvdal, Per
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Svensater, Gunnel
    Davies, Julia R.
    Crystalline anatase-rich titanium can reduce adherence of oral streptococci2014In: Biofouling (Print), ISSN 0892-7014, E-ISSN 1029-2454, Vol. 30, no 6, p. 751-759Article in journal (Refereed)
    Abstract [en]

    Dental implant abutments that emerge through the mucosa are rapidly covered with a salivary protein pellicle to which bacteria bind, initiating biofilm formation. In this study, adherence of early colonizing streptococci, Streptococcus gordonii, Streptococcus oralis, Streptococcus mitis and Streptococcus sanguinis to two saliva-coated anodically oxidized surfaces was compared with that on commercially pure titanium (CpTi). Near edge X-ray absorption (NEXAFS) showed crystalline anatase was more pronounced on the anodically oxidized surfaces than on the CpTi. As revealed by fluorescence microscopy, a four-species mixture, as well as individual bacterial species, exhibited lower adherence after 2 h to the saliva-coated, anatase-rich surfaces than to CpTi. Since wettability did not differ between the saliva-coated surfaces, differences in the concentration and/or configuration of salivary proteins on the anatase-rich surfaces may explain the reduced bacterial binding effect. Anatase-rich surfaces could thus contribute to reduced overall biofilm formation on dental implant abutments through diminished adherence of early colonizers.

  • 7.
    Farstad, M. H.
    et al.
    Norwegian Univ Sci & Technol, Dept Phys, NO-7491 Trondheim, Norway..
    Ragazzon, Davide
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Groenbeck, H.
    Chalmers, Competence Ctr Catalysis, SE-41296 Gothenburg, Sweden.;Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden..
    Strömsheim, M. D.
    Norwegian Univ Sci & Technol, Dept Chem Engn, NO-7491 Trondheim, Norway..
    Stavrakas, Camille
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Gustafson, J.
    Lund Univ, Div Synchrotron Radiat Res, Box 118, SE-22100 Lund, Sweden..
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Borg, A.
    Norwegian Univ Sci & Technol, Dept Phys, NO-7491 Trondheim, Norway..
    TiOx thin films grown on Pd(100) and Pd(111) by chemical vapor deposition2016In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 649, p. 80-89Article in journal (Refereed)
    Abstract [en]

    The growth of ultrathin TiOx (0 <= x <= 2) films on Pd(100) and Pd(111) surfaces by chemical vapor deposition (CVD), using Titanium(IV)isopropoxide (TTIP) as precursor, has been investigated by high resolution photoelectron spectroscopy, low energy electron diffraction and scanning tunneling microscopy. Three different TiOx phases and one Pd-Ti alloy phase have been identified for both surfaces. The Pd-Ti alloy phase is observed at the initial stages of film growth. Density functional theory (DFT) calculations for Pd(100) and Pd(111) suggest that Ti is alloyed into the second layer of the substrate. Increasing the TTIP dose yields a wetting layer comprising Ti2+ species (TiOx, x similar to 0.75). On Pd(100), this phase exhibits a mixture of structures with (3 x 5) and (4 x 5) periodicity with respect to the Pd(100) substrate, while an incommensurate structure is formed on Pd(111). Most importantly, on both surfaces this phase consists of a zigzag pattern similar to observations on other reactive metal surfaces. Further increase in coverage results in growth of a fully oxidized (TiO2) phase on top of the partially oxidized layer. Preliminary investigations indicate that the fully oxidized phase on both Pd(100) and Pd(111) may be the TiO2(B) phase.

  • 8.
    Farstad, M. H.
    et al.
    Norwegian Univ Sci & Technol, Dept Chem Engn, Trondheim.
    Ragazzon, Davide
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Strømsheim, M. D.
    Norwegian Univ Sci & Technol, Dept Chem Engn, Trondheim.
    Gustafson, J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Borg, A.
    Norwegian Univ Sci & Technol, Dept Phys, Trondheim.
    Oxidation and Reduction of TiOx Thin Films on Pd(111) and Pd(100)2018In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 122, no 2, p. 688-694Article in journal (Refereed)
    Abstract [en]

    Thin films of TiOx on Pd(100) and Pd(111) have been investigated with respect to their properties after oxidation and reduction cycles. High-resolution photoemission spectroscopy (HRPES) and low energy electron diffraction (LEED) have been applied to characterize the thin film oxidation states and structure before and after oxidation and reduction under ultrahigh vacuum conditions. Fully oxidized TiO2 films were formed on both surfaces. These structures display Moiré patterns in LEED, in one dimension for Pd(100) and in two dimensions for Pd(111), and they have previously not been reported for TiO2/Pd. The oxidation process causes strong reduction in the interaction between the oxide thin film and the Pd substrate, most significantly for Pd(111). Reversible oxidation/reduction cycling of TiOx thin films on Pd(111) and Pd(100) was possible.

  • 9. Farstad, M. H.
    et al.
    Ragazzon, Davide
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Walle, L. E.
    Schaefer, A.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Borg, A.
    Water Adsorption on TiOx Thin Films Grown on Au(111)2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 12, p. 6660-6669Article in journal (Refereed)
    Abstract [en]

    High resolution photoelectron spectroscopy has been used to investigate water adsorption on four different TiOx ultrathin film structures, grown on Au(111) by chemical vapor deposition. Two of the structures are reduced TiOx single layer phases, forming a honeycomb (HC) and a pinwheel (PW) structure, respectively. The other two phases have TiO2 stoichiometry, one in the form of islands and one in the form of a TiO2(B)(001) extended layer. Partial water dissociation is observed for all phases but the HC phase, and the dissociation propensity and adsorbate thermal stability structure result from interplay between the atomic structure of the particular TiOx phase and defects formed in the preparation. The dissociation on the TiO2(B) film is mainly related to different types of defect sites. The TiO2 islands, interpreted as surface reconstructed rutile TiO2(100), generate the highest amount of hydroxyls with a behavior consistent with reconstruction into a mixed (100) and (110) termination. Water dissociation on the PW layer can be assigned to particular sites of the structure and it stands out by leading to oxidation of Ti species.

  • 10.
    Henningsson, A
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Physics, Department of Physics and Materials Science, Physics I. Department of Physical and Analytical Chemistry, Physical Chemistry.
    Rensmo, H
    Department of Physics. Physics, Department of Physics and Materials Science, Physics I. Department of Physical and Analytical Chemistry, Physical Chemistry.
    Sandell, A
    Department of Physics. Physics, Department of Physics and Materials Science, Physics I. Department of Physical and Analytical Chemistry, Physical Chemistry.
    Siegbahn, H
    Department of Physics. Physics, Department of Physics and Materials Science, Physics I. Department of Physical and Analytical Chemistry, Physical Chemistry.
    Södergren, S
    Lindström, H
    Hagfeld, A
    Physics, Department of Physics and Materials Science, Physics I. Department of Physical and Analytical Chemistry, Physical Chemistry.
    Electronic structure of electrochemically Li-inserted TiO2 studied with synchrotron radiation electron spectroscopies2003In: Journal of Chemical Physics, Vol. 118, no 12, p. 5607-5612Article in journal (Refereed)
  • 11.
    Henningsson, Anders
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I.
    Rensmo, Håkan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I.
    Sandell, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I.
    Södergren, Sven
    Siegbahn, Hans
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I.
    Insertion of H+, Li+, Na+ and K+ into thin films prepared from silicotungstic acid - a photoelectron spectroscopy study2004In: Thin Solid Films, Vol. 461, no 2, p. 237-242Article in journal (Refereed)
  • 12.
    Henningsson, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Stashans, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Södergren, Sven
    Lindström, H.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Vayssieres, L.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Lunell, Sten
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry. Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics I.
    Proton insertion in polycrystalline WO3 studied with electron spectroscopy and semi-empirical calculations2004In: Advances in Quantum Chemistry, ISSN 0065-3276, E-ISSN 2162-8815, Vol. 47, p. 23-36Article in journal (Refereed)
  • 13. Jaworowski, A J
    et al.
    Asmundson, R
    Uvdal, P
    Sandell, A
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Fysik I.
    Determination of NO adsorption sites on Pd(100) using core level photoemission and low energy electron diffraction2002In: Surface Science, Vol. 501, no 1-2, p. 74-82Article in journal (Refereed)
  • 14. Jaworowski, A J
    et al.
    Uvdal, P
    Gray, S M
    Sandell, A
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Fysik I.
    Mn-induced NO dissociation on Pd(100)2002In: Surface Science, Vol. 501, no 1-2, p. 83-92Article in journal (Refereed)
  • 15.
    Johansson, E
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Platzer-Björkman, C
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Rensmo, H
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Sandell, A
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Stolt, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Gorgoi, M
    Svensson, S
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Schäfers, F
    Braun, W
    Eberhardt, W
    HIKE experiments at KMC-1: Studies of Solar Cell Materials2007In: Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung m.b.H. (BESSY) Annual Report (2006), no 508-509Article in journal (Refereed)
  • 16.
    Johanssson, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Mahrov, Boriss
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Figgemeier, E
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Jönsson, Stina
    Fahlman, Mats
    Interfacial properties of photovoltaic TiO2/dye/PEDOT–PSS heterojunctions2005In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 149, no 2-3, p. 157-167Article in journal (Refereed)
    Abstract [en]

    Systems comprising a dense TiO2 film electrode, a ruthenium polypyridine dye and a PEDOT-PSS (poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulphonate)) film were prepared. The heterojunctions were shown to have photovoltaic properties, with the dye absorbing the light, the TiO2 acting as an electron conducting material and PEDOT-PSS acting as a hole transport material. A series of dyes was used to investigate their influence on the photocurrent and the photovoltage characteristics of the heterojunction. These results were compared to a photoelectrochemical system in which the PEDOT-PSS was replaced by a liquid electrolyte containing triiodide/iodide redox-couple.Photoelectron spectroscopy (PES) was used to monitor the interfacial properties of the heterojunction and the investigation points out effects of importance when assembling the materials together to a functional unit. Specifically, it was concluded that the interaction with the dye clearly affects the structure of PEDOT-PSS, both with respect to the surface composition of PSS relative to PEDOT and with respect to the chemical state of the sulphur in the polymers. Moreover, a comparison of the Ru3d and the valence band spectra of the two different interfaces (dye/TiO2 and dye/PEDOT-PSS) indicates that the energy level structure of the dyes compared to the substrate is different for the two surfaces. Thus, in the combined energy level picture under dark conditions, the energy levels in TiO2 relative to the energy levels in PEDOT-PSS depend on the dye.

  • 17.
    Karis, Olof
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Experimental Physics. Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Department of Materials Chemistry, Inorganic Chemistry.
    Valizadeh, Sima
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Experimental Physics. Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Department of Materials Chemistry, Inorganic Chemistry. Elektronmikroskopi.
    Surpi, Alessandro
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Experimental Physics. Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Department of Materials Chemistry, Inorganic Chemistry. Istituto di Fotonica e Nanotecnologie (C.N.R.).
    HUNTER DUNN, J
    MAX-lab, Lund, Sweden..
    SVEDLINDH, PETER
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Experimental Physics. Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Department of Materials Chemistry, Inorganic Chemistry.
    Stanciu, V
    Warnicke, P
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Experimental Physics. Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Department of Materials Chemistry, Inorganic Chemistry.
    Sandell, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Experimental Physics. Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Department of Materials Chemistry, Inorganic Chemistry.
    Nyholm, Leif
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Experimental Physics. Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Sanyal, Biplab
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Experimental Physics. Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Department of Materials Chemistry, Inorganic Chemistry.
    Eriksson, Olle
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Experimental Physics. Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Department of Materials Chemistry, Inorganic Chemistry.
    Electronic and geometric structure of (Zn,Co)O room temperature Ferromagnets2005In: 50th MMM Meeting Program, 2005Conference paper (Refereed)
  • 18. Karlsson, P. G.
    et al.
    Richter, J. H.
    Andersson, M. P.
    Johansson, M. K-J
    Blomquist, J.
    Uvdal, P.
    Sandell, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    TiO2 chemical vapor deposition on Si(111) in ultrahigh vacuum: Transition from interfacial phase to crystalline phase in the reaction limited regime2011In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 605, no 13-14, p. 1147-1156Article in journal (Refereed)
    Abstract [en]

    The interaction between the metal organic precursor molecule titanium(IV) isopropoxide (TTIP) and three different surfaces has been studied: Si(111)-(7 x 7), SiOx/Si(111) and TiO2. These surfaces represent the different surface compositions encountered during TTIP mediated TiO2 chemical vapor deposition on Si(111). The surface chemistry of the titanium(IV) isopropoxide precursor and the film growth have been explored by core level photoelectron spectroscopy and x-ray absorption spectroscopy using synchrotron radiation. The resulting film morphology has been imaged with scanning tunneling microscopy. The growth rate depends on both surface temperature and surface composition. The behavior can be rationalized in terms of the surface stability of isopropoxy and isopropyl groups, confirming that growth at 573 K is a reaction limited process.

  • 19.
    Karlsson, Patrik
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Bolik, Sara
    Richter, Jan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Mahrov, Boriss
    Department of Physical Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Johansson, E M J
    Blomquist, J
    Uvdal, P
    Rensmo, Håkan
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Siegbahn, Hans
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Sandell, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Interfacial properties of the nanostructured dye-sensitized solid heterojunction TiO2/RuL2(NCS)(2)/CuI2004In: Journal of Chemical Physics, Vol. 120, no 23, p. 11224-11232Article in journal (Refereed)
  • 20.
    Karlsson, Patrik
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Fysik 1.
    Richter, Jan Hinnerk
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I.
    Andersson, M P
    Blomquist, J
    Siegbahn, Hans
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I.
    Uvdal, P
    Sandell, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I.
    UHV-MOCVD growth of TiO2 on SiOx/Si(111): Interfacial properties reflected in the Si 2p photoemission spectra2005In: Surface Science, Vol. 580, no 1-3, p. 207-217Article in journal (Refereed)
  • 21.
    Lewin, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Johansson, E
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Sandell, A
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Gorgoi, M
    Schäfers, F
    Braun, W
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Stüber, M
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Svensson, S
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Eberhardt, W
    HIKE experiments at KMC-1: Recent Analysis of Thin Film Nanocomposites2007In: Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung m.b.H. (BESSY) Annual Report (2006), p. 503-504Article in journal (Other academic)
  • 22.
    Lewin, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Persson, P.O.Å
    Lattermann, M
    Stüber, M
    Gorgoi, M
    Sandell, A
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Ziebert, C
    Schäfers, F
    Braun, W
    Halbritter, J
    Ulrich, S
    Eberhard, W
    Hultman, L
    Siegbahn, H
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Svensson, S
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    On the origin of a third spectral component of C1s XPS-spectra for nc-TiC/a-C nanocomposite thin films2008In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 202, no 15, p. 3563-3570Article in journal (Refereed)
    Abstract [en]

    X-ray photoelectron spectroscopy (XPS) spectra of sputter-etched nc-TiC/a-C nanocomposite thin films published in literature show an extra feature of unknown origin in the C1s region. This feature is situated between the contributions of carbide and the carbon matrix. We have used high kinetic energy XPS (HIKE-XPS) on magnetron-sputtered nc-TiC/a-C thin films to show that this feature represents a third chemical environment in the nanocomposites, besides the carbide and the amorphous carbon. Our results show that component is present in as-deposited samples, and that the intensity is strongly enhanced by Ar+-ion etching. This third chemical environment may be due to interface or disorder effects. The implications of these observations on the XPS analysis of nanocomposites are discussed in the light of overlap problems for ternary carbon based systems.

  • 23. Nilsson, B
    et al.
    Adler, J O
    Andersson, B E
    Annand, J R M
    Akkurt, I
    Boland, M J
    Crawford, G I
    Fissum, K G
    Hansen, K
    Harty, P D
    Ireland, D G
    Isaksson, L
    Karlsson, M
    Lundin, M
    McGeorge, J C
    Miller, G J
    Ruijter, H
    Sandell, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I.
    Schroder, B
    Sims, D A
    Watts, D
    Near-threshold measurement of the He-4(gamma,n) reaction2005In: Physics Letters B, Vol. 626, p. 65-71Article in journal (Refereed)
  • 24.
    Nilsson, Johan O.
    et al.
    KTH Royal Inst Technol, Dept Mat Sci & Engn, Brinellvagen 23, S-10044 Stockholm, Sweden..
    Leetmaa, Mikael
    KTH Royal Inst Technol, Dept Mat Sci & Engn, Brinellvagen 23, S-10044 Stockholm, Sweden..
    Wang, Baochang
    Chalmers Univ Technol, Dept Phys, S-41296 Gothenburg, Sweden.;Chalmers Univ Technol, Competence Ctr Catalysis, S-41296 Gothenburg, Sweden..
    Zguns, Pjotrs A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. KTH Royal Inst Technol, Dept Mat Sci & Engn, Brinellvagen 23, S-10044 Stockholm, Sweden.
    Pasti, Igor
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia..
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Skorodumova, Natalia V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. KTH Royal Inst Technol, Dept Mat Sci & Engn, Brinellvagen 23, S-10044 Stockholm, Sweden.
    Modeling Kinetics of Water Adsorption on the Rutile TiO2 (110) Surface: Influence of Exchange-Correlation Functional2018In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 255, no 3, article id 1700344Article in journal (Refereed)
    Abstract [en]

    The accuracy of the theoretical description of materials properties in the framework of density functional theory (DFT) inherently depends on the exchange-correlation (XC) functional used in the calculations. Here we investigate the influence of the choice of a XC functional (PBE, RPBE, PW91, and PBE0) on the kinetics of the adsorption, diffusion and dissociation of water on the rutile TiO2(110) surface using a combined Kinetic Monte Carlo (KMC) - DFT approach, where the KMC simulations are based on the barriers for the aforementioned processes calculated with DFT. We also test how the adsorption energy of intact and dissociated water molecules changes when dispersion interactions are included into the calculations. We consider the beginning of the water layer formation varying coverage up to 0.2 monolayer (ML) at temperatures up to 180K. We demonstrate that the dynamics of the simulated water-titania system is extremely sensitive to the choice of the XC functional.

  • 25.
    Olovsson, W
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV. Physics I.
    Holmström, E
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV. Physics I.
    Sandell, A
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV. Physics I.
    Abrikosov, I A
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV. Physics I.
    Core-level shifts for surface bimetallic systems from first-principles theory: Pd-Mn structures on Pd(100)2003In: Physical Review B, Vol. 68, no 4, p. 045411-Article in journal (Refereed)
  • 26.
    Ragazzon, Davide
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Farstad, Mari Helene
    Norwegian University of Science and Technology (NTNU).
    Schaefer, Andreas
    University of Bremen.
    Walle, Lare Erik
    Norwegian University of Science and Technology (NTNU).
    Uvdal, Per
    Lund University.
    Borg, Anne
    Norwegian University of Science and Technology (NTNU).
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Growth of TiO2(B)(001) on Au(111) by Chemical Vapor Deposition2015In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 633, p. 102-108Article in journal (Refereed)
    Abstract [en]

    This study presents how a TiO2(B) film exposing the (001) face can be grown on Au(111) by chemical vapor deposition. Identification and characterization of the TiO2(B)(001) layer are carried out with low-energy electron diffraction (LEED), synchrotron radiation photoelectron spectroscopy (PES), scanning tunneling microscopy (STM) and X-ray absorption spectroscopy (XAS). Formation of the TiO2(B) film requires a two-step preparation procedure: deposition at 280 °C followed by annealing to 500 °C. This suggests that the interaction between a substrate and an overlayer stabilizes the TiO2(B) film, preventing the formation of thermodynamically more stable rutile islands. The study thus gives insight into how the morphology and the atomic structure of the titania overlayer can be controlled.

  • 27.
    Ragazzon, Davide
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Schaefer, A.
    Farstad, M. H.
    Walle, L. E.
    Palmgren, P.
    Borg, A.
    Uvdal, P.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Chemical vapor deposition of ordered TiOx nanostructures on Au(111)2013In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 617, p. 211-217Article in journal (Refereed)
    Abstract [en]

    The deposition of TiOx (x <= 2) structures on Au(111) by chemical vapor deposition (CVD) in ultrahigh vacuum (UHV) has been investigated with high-resolution core level photoelectron spectroscopy (PES), low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Using titanium tetra-isopropoxide as single source precursor it is possible to form different TiOx phases on the surface after deposition: at low coverages, we observe large two-dimensional (2D) honeycomb-lattice Ti2O3 islands with a (2 x 2) registry with the substrate. Higher coverages are dominated by the formation of three-dimensional (3D) TiO2 structures. The TiO2 structures are atomically well ordered provided that the deposition temperature is high enough (500 degrees C). The ordered structure exhibits a LEED pattern characteristic for a rectangular surface unit cell. By performing the deposition at different temperatures it is possible to tune the balance between the 2D and 3D phases: Growth at 500 degrees C significantly favors the formation of 3D TiO2 islands as compared to growth at 200 degrees C and 300 degrees C.

  • 28.
    Richter, Jan Hinnerk
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I.
    Henningsson, Anders
    Karlsson, Patrik
    Department of Physics and Materials Science, Physics I.
    Andersson, M P
    Uvdal, P
    Siegbahn, Hans
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I.
    Sandell, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I.
    Electronic structure of lithium-doped anatase TiO2 prepared in ultrahigh vacuum2005In: Physical Review B, Vol. 71, no 23Article in journal (Refereed)
  • 29.
    Richter, Jan Hinnerk
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Theoretical Magnetism. Fysik 1.
    Henningsson, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Theoretical Magnetism.
    Sanyal, Biplab
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Theoretical Magnetism. Theoretical Magnetism.
    Karlsson, Patrik
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Theoretical Magnetism. Fysik 1.
    Andersson, M. P.
    Uvdal, P
    Siegbahn, Hans
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Theoretical Magnetism. Fysik 1.
    Eriksson, Olle
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Theoretical Magnetism. Theoretical Magnetism.
    Sandell, Anders
    Department of Physics and Materials Science, Physics I. Theoretical Magnetism. Fysik 1.
    Phase separation and charge localization in UHV-lithiated anatase TiO2 nanoparticles2005In: Physical Review B, ISSN 1098-0121, Vol. 71, no 23, p. 235419-Article in journal (Refereed)
    Abstract [en]

    The insertion of lithium in anatase TiO2 nanoparticles under ultrahigh vacuum (UHV) conditions is studied using x-ray absorption spectroscopy (XAS) and resonant photoelectron spectroscopy (RPES) at the Ti L2,3 edge. It is demonstrated that XAS can be used to monitor the separation into an anatase phase and a lithium titanate phase of formal stoichiometry Li0.5TiO2. The initial state properties of the Ti 3d states of the lithium titanate phase are investigated using ab initio electronic structure calculations. The calculations show a correlation driven separation of Ti 3d states from the conduction band in agreement with previous studies. It is shown that Ti in different oxidation states (Ti3+ and Ti4+) is formed as a direct consequence of the electron-electron interaction. RPES and XAS spectra confirm the presence of electronically inequivalent Ti sites. The site-sensitivity of the RPES spectra at selected electron binding energies is found to be consistent with the calculations.

  • 30.
    Sandell, A
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V. Fysik 1.
    Andersson, M P
    Alfredsson, Y
    Department of Physics and Materials Science, Physics I. Physics V.
    Johansson, M K-J
    Schnadt, J
    Rensmo, H
    Department of Physics and Materials Science, Physics I. Physics V.
    Siegbahn, H
    Department of Physics and Materials Science, Physics I. Physics V.
    Uvdal, P
    Titanium dioxide thin film growth on silicon (111) by chemical vapor deposition of titanium(IV) isopropoxide2002In: Journal of Applied Physics, Vol. 92, p. 3381-Article in journal (Refereed)
  • 31.
    Sandell, A
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Fysik 1.
    Andersson, M P
    Jaworowski, A J
    Roberts, J T
    Uvdal, P
    Surface chemistry of TiCl4 on W(110): Identification of surface intermediates2002In: Surface Science, Vol. 521, p. 129-Article in journal (Refereed)
  • 32.
    Sandell, A
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V.
    Andersson, M P
    Johansson, M K J
    Karlsson, P
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V.
    Alfredsson, Y
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V.
    Schnadt, J
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V.
    Siegbahn, H
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V.
    Uvdal, P
    Metalorganic chemical vapor deposition of anatase titanium dioxide on Si: Modifying the interface by pre-oxidation2003In: Surface science, Vol. 530, no 1-2, p. 63-70Article in journal (Other scientific)
  • 33.
    Sandell, A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Theory.
    Walle, L. E.
    Richter, J. H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Plogmaker, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Karlsson, P. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Surface and Interface Science.
    Borg, A.
    Uvdal, P.
    Probing and modifying the empty-state threshold of anatase TiO2: Experiments and ab initio theory2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 7, p. 075113-Article in journal (Refereed)
    Abstract [en]

    O 1s x-ray absorption spectroscopy (XAS) in conjunction with photoelectron spectroscopy has been used to explore the conduction-band edge of single crystalline and nanostructured anatase TiO2. The experiments are supported by ab initio density-functional calculations in which both the initial and core hole final states are considered. The calculations show that the states at the conduction-band edge of anatase are of pure d(xy) character. This is also the case in the presence of an O 1s core hole. In the O 1s XAS process pure Ti d states cannot be probed and, by appropriate energy referencing, the separation between the Ti d derived conduction-band edge and the threshold of the unoccupied Ti d-O p states can therefore be revealed. The electronic charge needed per Ti to eliminate this offset is discussed in quantitative terms. The theoretical and experimental values are in good agreement, showing that 4 +/- 2% of an electronic charge per Ti ion is sufficient to change the character of the empty states at threshold from pure Ti d to Ti d-O p.

  • 34.
    Sandell, Anders
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I.
    Jaworowski, A J
    The Mn 2p core-level photoelectron spectrum of Pd-Mn bimetallic systems on Pd(100)2004In: Journal of Electron Spectroscopy and Related Phenomena, Vol. 135, no 1, p. 7-14Article in journal (Refereed)
  • 35.
    Sandell, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Karlsson, Patrik G.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Richter, J. H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Blomquist, J.
    Uvdal, P.
    Surface chemistry of HfI4 on Si(100)-(2x1) studied by core level photoelectron spectroscopy2007In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 601, no 4, p. 917-923Article in journal (Refereed)
    Abstract [en]

    The chemistry of HfI4 adsorbed on the Si(100)-(2 x 1) surface has been studied by core level photoelectron spectroscopy in ultra-high vacuum. Two stable surface intermediates are identified: HfI3 and HfI2, both of which remain upon heating to 690 K. The dissociation of HfI4 is accompanied by the formation of SiI. In addition, HfI4 is observed up to 300 K. Complete desorption of iodine occurs in the temperature regime 690-780 K. Deposition of HfI4 at 870 K results in a layer consisting of metallic Hf, whereas deposition at 1120 K results in the formation of Hf silicide. The results indicate that the metallic Hf formed at 870 K is in the form of particles. Oxidation of this film by O2 at low pressure does not result in complete Hf oxidation. This suggests that complete oxidation of Hf is a critical step when using HfI4 as precursor in atomic layer deposition.

  • 36.
    Sandell, Anders
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Fysik 1.
    Karlsson, Patrik
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I.
    Richter, Jan Hinnerk
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I.
    Blomquist, J
    Uvdal, P
    Grehk, T M
    Growth of ultrathin ZrO2 films on Si(100): Film thickness dependent band alignment2006In: Applied Physics Letters, Vol. 88, no 13, p. 132905-Article in journal (Refereed)
  • 37.
    Sandell, Anders
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V. Fysik 1.
    Karlsson, Patrik
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V.
    Richter, Jan Hinnerk
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V.
    Göthelid, Emmanuelle
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V.
    Uvdal, P
    Blomquist, J
    Grehk, T M
    Zirconium Dioxide Formation on Silicon Surfaces by Metal-Organic Chemical Vapor Deposition in UHV2006In: AVS 53, 2006Conference paper (Other (popular scientific, debate etc.))
  • 38.
    Sandell, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Ragazzon, Davide
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Schaefer, A.
    Lund Univ, Div Synchrotron Radiat Res, Box 118, SE-22100 Lund, Sweden..
    Farstad, M. H.
    Norwegian Univ Sci & Technol NTNU, Dept Phys, NO-7491 Trondheim, Norway..
    Borg, A.
    Norwegian Univ Sci & Technol NTNU, Dept Phys, NO-7491 Trondheim, Norway..
    Photochemistry of Carboxylate on TiO2(110) Studied with Synchrotron Radiation Photoelectron Spectroscopy2016In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, no 44, p. 11456-11464Article in journal (Refereed)
    Abstract [en]

    We present a dedicated synchrotron radiation photoelectron spectroscopy (SR-PES) study of a photochemical reaction on the surface of rutile TiO2(110). The photoreaction kinetics of carboxylate species (trimethyl acetate, TMA) upon irradiation by UV and soft X-rays were monitored, and we show that it is possible to control the reaction rates from UV light and soft X-rays independently. We directly observe Ti4+ -> Ti3+ conversion upon irradiation, attributed to electron trapping at Ti sites close to surface OH groups formed by deprotonation of the parent molecule, trimethylacetic acid (TMAA). TMA photolysis on two surface preparations with different oxygen vacancy densities shows that the vacancy-related charge quenches the amount of charge that can be trapped at hydroxyls upon irradiation. During the initial stages of reaction the correlation between the amount of photodepleted TMA and the amount of charge trapped in the Ti 3d band gap state is nearly 1:1. A first-order kinetics analysis reveals that the reaction rate decreases with decreasing TMA coverage. There is also a coverage-dependent difference in the electronic structure of TMA moieties, primarily involving the carboxyl anchor group. These changes are consistent with a decreased hole affinity of the adsorbed TMA and hence a decreased reaction rate. This discovery adds to the previously presented picture of a reactivity that is inversely proportional to the number of surface hydroxyls, suggesting that the balance between the amounts of TMA, OH, and trapped charge needs to be considered.

  • 39.
    Sandell, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Walle, L. E.
    Uvdal, P.
    Borg, A.
    Probing the conduction band edge of transition metal oxides by X-ray absorption spectroscopy2011In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 183, no 1-3, p. 107-113Article in journal (Refereed)
    Abstract [en]

    We present a comprehensive picture of how X-ray absorption spectroscopy (XAS) at the O 1s edge, supported by ob initio calculations, can be used to address the electronic properties of the conduction band edges of transition metal oxides. The compounds studied in order to illustrate the method are two of the most versatile transition metal oxides, ZrO2 and TiO2. Special attention is paid to the subtler aspects of the approach, discussing in more detail the kind of information provided and also possible shortcomings and complications. It is shown that the interpretation of the relationship between the Fermi level-referenced O 1s PES peak and the O 1s is XAS spectrum can change depending on the electronic properties of the material under study. In order to fully understand the PES-XAS relationship, supporting information from calculations is essential.

  • 40.
    Sandell, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Schaefer, A.
    Lund Univ, Dept Synchrotron Radiat Res, POB 118, SE-22100 Lund, Sweden..
    Ragazzon, Davide
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Farstad, M. H.
    NTNU Norwegian Univ Sci & Technol, Dept Phys, NO-7491 Trondheim, Norway..
    Borg, A.
    NTNU Norwegian Univ Sci & Technol, Dept Phys, NO-7491 Trondheim, Norway..
    Adsorption and photolysis of trimethyl acetate on TiO2(B)(001) studied with synchrotron radiation core level photoelectron spectroscopy2017In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 666, p. 104-112Article in journal (Refereed)
    Abstract [en]

    We present a synchrotron radiation photoelectron spectroscopy study of the adsorption and photooxidation of trimethyl acetate (TMA) on TiO2(B)(001). The TiO2(B)(001) substrate was realized in the form of 2nm thick film on Au(111). The TMA species adopt the bidentate bonding configuration, as expected for carboxylic acids on TiO2, but cannot coordinate to all surface Ti ions due to steric hindrance. The proposed arrangement of the TMA species thus allows for the formation of an overlayer with a (2 x 1) periodicity. The thermal stability is found to be comparable to that on rutile (110) although the results indicate differences in the threshold for the TMA+H -> TMAA reaction. Photolysis using both ultraviolet (UV) light and soft x-ray synchrotron radiation (SR) was studied and compared to the reaction on the reduced ruffle (110) surface. A kinetic analysis suggests that the photoreaction rate for TMA on the TiO2(B) thin film is initially two times faster than that on the reduced rutile TiO2(110) surface. The higher activity of the TiO2(B) film is assigned to a reduced influence from surplus electrons associated with reduced Ti species, thereby decreasing the probability for hole-annihilation at high TMA coverage.

  • 41.
    Sandell, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Walle, L. E.
    Blomquist, J.
    Uvdal, P.
    Borg, A.
    Heterogeneous reaction between Li and anatase TiO2 nanoparticles under ultra-high vacuum2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 29, p. 12283-12290Article in journal (Refereed)
    Abstract [en]

    We demonstrate heterogeneous chemistry between Li and anatase TiO2 nanoparticles under UHV. The reduction of TiO2 upon formation of lithium oxide proceeds via two different schemes: one that reduces Ti4+ to Ti3+ and one that reduces Ti4+ directly to Ti2+. The second scheme sets in only after a critical degree of reduction (i.e. Li amount) has been reached (Li/Ti = 0.28) and is associated with restructuring of the film. Two films with different morphologies were compared and the results demonstrate that the reaction between Li and larger TiO2 structures (30-50 nm) is kinetically restricted while such effects were significantly less prominent for small particles (10 nm).

  • 42.
    Schaefer, A.
    et al.
    Chalmers Univ Technol, Competence Ctr Catalysis, S-41296 Gothenburg, Sweden;Chalmers Univ Technol, Dept Chem & Chem Engn, S-41296 Gothenburg, Sweden.
    Lanzilotto, Valeria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Cappel, Ute B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, Stockholm, Sweden.
    Uvdal, P.
    Lund Univ, Dept Chem, Chem Phys, POB 124, SE-22100 Lund, Sweden.
    Borg, A.
    NTNU Norwegian Univ Sci & Technol, Dept Phys, NO-7491 Trondheim, Norway.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Defect-Induced Water Bilayer Growth on Anatase TiO2(101)2018In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 37, p. 10856-10864Article in journal (Refereed)
    Abstract [en]

    Preparing an anatase TiO2(101) surface with a high density of oxygen vacancies and associated reduced Ti species in the near-surface region results in drastic changes in the water adsorption chemistry compared to adsorption on a highly stoichiometric surface. Using synchrotron radiation excited photoelectron spectroscopy, we observe a change in the water growth mode, from layer-by-layer growth on the highly stoichiometric surface to bilayer growth on the reduced surface. Furthermore, we have been able to observe enrichment at the surface upon water adsorption. The Ti3+ enrichment occurs concomitant with effective water dissociation into hydroxyls with a very high thermal stability. The water bilayer on the reduced surface is thermally more stable than that on the stoichiometric surface, and it is more efficient in promoting further water dissociation upon heating. The results thus show how the presence of subsurface defects can alter the wetting mechanism of an oxide surface.

  • 43.
    Schaefer, A.
    et al.
    Lund Univ, Dept Synchrotron Radiat Res, POB 118, SE-22100 Lund, Sweden;Chalmers Univ Technol, Competence Ctr Catalysis, S-41296 Gothenburg, Sweden.
    Lanzilotto, Valeria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Cappel, Ute B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, Stockholm, Sweden.
    Uvdal, P.
    Lund Univ, Dept Chem, Chem Phys, POB 124, SE-22100 Lund, Sweden.
    Borg, A.
    NTNU Norwegian Univ Sci & Technol, Dept Phys, NO-07491 Trondheim, Norway.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    First layer water phases on anatase TiO2(101)2018In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 674, p. 25-31Article in journal (Refereed)
    Abstract [en]

    The anatase TiO2(101) surface and its interaction with water is an important topic in oxide surface chemistry. Firstly, it benchmarks the properties of the majority facet of TiO2 nanoparticles and, secondly, there is a controversy as to whether the water molecule adsorbs intact or deprotonates. We have addressed the adsorption of water on anatase TiO2(101) by synchrotron radiation photoelectron spectroscopy. Three two-dimensional water structures are found during growth at different temperatures: at 100 K, a metastable structure forms with no hydrogen bonding between the water molecules. In accord with prior literature, we assign this phase to chains of disordered molecules. Growth 160 K results in a metastable structure with expressed hydrogen bonding between the water molecules. At 190 K, the water molecules become disordered as the thermal energy is too high and hence the hydrogen bonds break. The result is a structure with isolated monomers. Partial dissociation is observed for all three growths, with the molecular state only slightly favored in energy (20-40 meV) over the dissociated state. Heating of a thick film leads to more dissociation compared to a bilayer, when formed at 100 K. Thus, extending the water network facilitates proton transport and hence dissociation. The results reconcile apparent conflicting experimental results previously obtained by scanning tunneling microscopy (STM) and core level photoelectron spectroscopy.

  • 44. Schaefer, A.
    et al.
    Ragazzon, Davide
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Walle, L. E.
    Farstad, M. H.
    Wichmann, A.
    Baeumer, M.
    Borg, A.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Controlled modification of nanoporous gold: Chemical vapor deposition of TiO2 in ultrahigh vacuum2013In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 282, p. 439-443Article in journal (Refereed)
    Abstract [en]

    TiO2 has been deposited in the first 400 nm of a nanoporous gold (NPG) structure using metal organic chemical vapor deposition with titanium-tetraisopropoxide as single source precursor in ultra high vacuum. The NPG has been pretreated by ozone to clean and stabilize the structure for deposition. The deposited oxide stabilizes the porous structure, otherwise prone to coarsening at elevated temperatures, up to 300 degrees C. The study combines the controlled sample preparation with a functional test of the prepared catalyst under real conditions in a continuous gas flow reactor. The catalytic activity of the loaded NPG at 60 degrees C for CO oxidation is found to be superior to unloaded as-prepared NPG.

  • 45. Schaefer, A.
    et al.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Walle, L. E.
    Zielasek, V.
    Schowalter, M.
    Rosenauer, A.
    Baeumer, M.
    Chemistry of thin film formation and stability during praseodymium oxide deposition on Si(111) under oxygen-deficient conditions2010In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 604, no 15-16, p. 1287-1293Article in journal (Refereed)
    Abstract [en]

    The growth of thin praseodymium oxide films on silicon (111) using small deposition rates under oxygen-deficient conditions was investigated in the range from submonolayer up to six monolayers coverage by transmission electron microscopy (TEM) and photoemission spectroscopy (PES). A detailed analysis of the silicon 2p and oxygen 1 s core level and valence band spectra reveals chemical reactions between deposited species, substrate, and the growing film. Silicate, silicide and oxide species are coexisting over the entire range of coverages investigated. Cross sectional TEM shows silicide inclusions extending from the surface several nanometers into the substrate and affecting the substrate band bending at the interface. The reactivity of the praseodymia overlayer leads to reactions in the as-deposited film even at room temperature and render it unstable. The article aims at providing a coherent picture of the chemistry proceeding during interface formation and film growth at low rates of deposition (0.06 nm/min). The results will be discussed in comparison to studies using higher rates, emphasizing the possibility of growth rate dependent reactions between substrate and deposited material and, consequently, distinctly different film compositions and structures for different rates of deposition. (C) 2010 Elsevier B.V. All rights reserved.

  • 46. Schaefer, A
    et al.
    Zielasek, V
    Schmidt, Th
    Sandell, A
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Schowalter, M
    Seifarth, O
    Walle, E
    Schulz, Ch
    Wollschlaeger, J
    Schroeder, T
    Rosenauer, A
    Falta, J
    Baeumer, M
    Growth of praseodymium oxide on Si(111) under oxygen-deficient conditions2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, no 4, p. 045414-Article in journal (Refereed)
    Abstract [en]

    Surface science studies of thin praseodymium oxide films grown on silicon substrates are of high interest in view of applications in such different fields as microelectronics and heterogeneous catalysis. In particular, a detailed characterization of the growth and the final structure of the films are mandatory to achieve a fundamental understanding of such topics as oxygen mobility and defect structure, and their role for the electronic and chemical properties. In this paper, the MBE growth of praseodymium oxide films on Si(111) substrates was investigated at low-deposition rates (0.06 nm/min) and low-oxygen partial pressures (p(O-2)<1 x 10(-10) mbar). To obtain insight into the structure and chemical composition of the growing film, spot profile analyzing low-energy electron diffraction (SPA-LEED), transmission electron microscopy, and synchrotron radiation-based x-ray photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy (XAS) were applied. SPA-LEED reveals the formation of an initial closed layer followed by continuous roughening and formation of ordered three-dimensional structures. This result is in contrast to observations at higher-deposition rates, were a layer-by-layer growth was reported. XAS and XPS provide evidence that a continuous reaction takes place in the growing Pr2O3 film leading to the formation of silicate and silicide structures within the film. Combining all data, a consistent picture of the deposition of praseodymium oxide on Si(111) emerges which clearly shows that in contrast to higher-throughput molecular beam epitaxy conditions the reactivity of the growing film strongly influences the growth behavior at low-deposition rates and low pressures.

  • 47.
    Schaefer, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Ragazzon, Davide
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Wittstock, A.
    Walle, L. E.
    Borg, A.
    Baeumer, M.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Toward Controlled Modification of Nanoporous Gold: A Detailed Surface Science Study on Cleaning and Oxidation2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 7, p. 4564-4571Article in journal (Refereed)
    Abstract [en]

    Nanostructured metals and especially unsupported nanoporous gold (np-Au) have attracted considerable attention in a variety of fields because of their special surface chemical properties. For applications in catalysis and sensorics, the oxidation, of the metal and the availability of oxygen at the very surface are crucial and also are capable of altering structural properties. In this article, we will discuss the state of the np-Au surface after annealing in vacuum. We shed light on the nature of Au-oxide obtained after cleaning the surface from carbon impurities with atomic oxygen provided by ozone decomposition, and we consider the effect of this procedure on silver residues. The results provide new insight into possible oxide species at the np-Au surface and represent a vital step toward controlled modification of the np-Au surface in the future.

  • 48.
    Schnadt, Joachim
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V.
    Henningsson, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V.
    Andersson, M.P
    Karlsson, Patrik
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V.
    Uvdal, P
    Siegbahn, Hans
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V.
    Bruhwiler, Paul
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V.
    Sandell, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics I. Physics V.
    Adsorption and charge transfer study of bi-isonicotinic acid on in situ grown anatase TiO2 nanoparticles2004In: Journal of Physical Chemistry B, Vol. 108, no 10, p. 3114-3122Article in journal (Other scientific)
  • 49.
    Stefanuik, Robert
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Knut, Ronny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Jana, Somnath
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Terschlüsen, Joachim A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Developments and enhancements to the HELIOS pump probe system2018In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 224, p. 33-37Article in journal (Refereed)
    Abstract [en]

    In this progress report we describe several design improvements that have been implemented at the HELIOS laboratory, as well as presenting the output characteristics that have been measured as a result. The main focus will be on the redesign of the gas cell, which has enhanced the photon flux of the XUV probe beam. Also, a frequency trippler utilizing sum frequency generation has been installed at the end of the pump line, which increases the photon flux available for both 3.1 eV (400 nm) and 4.66 eV (266 nm) applications without significant increment in the pulse width of the pump.

  • 50. Walle, L. E.
    et al.
    Agnoli, S.
    Svenum, I. -H
    Borg, A.
    Artiglia, L.
    Krueger, P.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Granozzi, G.
    High resolution photoemission and x-ray absorption spectroscopy of a lepidocrocite-like TiO(2) nanosheet on Pt(110) (1 x 2)2011In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 135, no 5, p. 054706-Article in journal (Refereed)
    Abstract [en]

    The electronic structure of TiO(2) nanosheets on the Pt(110)-(1 x 2) surface has been investigated by using high resolution photoemission spectroscopy and x-ray absorption spectroscopy (XAS). The Ti 2p XAS spectra of the deposited TiO(2) films have been theoretically evaluated and, from the comparison with the experimental data, the assignment to a lepidocrocite-like structure is confirmed. Coexistence of TiO(2) islands with PtO(2) stripes for incomplete nanosheets is confirmed by high resolution photoemission data. The location of the valence and conduction band edges of the nanosheet has been experimentally determined allowing us to describe in details subtle electronic effects due to the interface with the substrate. The locations of the valence band maximum and the leading peak in the O 1s XAS spectrum indicate a band gap similar to anatase but with the Fermi level closer to mid-gap than found for bulk, n-type TiO(2).

12 1 - 50 of 54
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