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  • 1.
    Ahmadi, Sareh
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Yu, Shun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Sun, Chenghua
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Reduced Au-MPc hole injection barrier by an intermediate iodine layerManuscript (preprint) (Other academic)
  • 2.
    Ahmadi, Sareh
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Yu, Shun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Zuleta, Marcelo
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Palmgren, Pål
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Charge transfer and band bending on TiO2(110)-MgPcManuscript (preprint) (Other academic)
  • 3. An, Wei
    et al.
    Baber, Ashleigh E.
    Xu, Fang
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Stacchiola, Dario
    Liu, Ping
    Mechanistic Study of CO Titration on CuxO/Cu(111) (x <= 2) Surfaces2014In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 6, no 8, p. 2364-2372Article in journal (Refereed)
    Abstract [en]

    The reducibility of metal oxides is of great importance to their catalytic behavior. Herein, we combined ambient-pressure scanning tunneling microscopy (AP-STM), X-ray photoemission spectroscopy (AP-XPS), and DFT calculations to study the CO titration of CuxO thin films supported on Cu(111) (CuxO/Cu(111)) aiming to gain a better understanding of the roles that the Cu(111) support and surface defects play in tuning catalytic performances. Different conformations have been observed during the reduction, namely, the 44 structure and a recently identified (5-7-7-5) Stone-Wales defects (5-7 structure). The DFT calculations revealed that the Cu(111) support is important to the reducibility of supported CuxO thin films. Compared with the case for the Cu2O(111) bulk surface, at the initial stage CO titration is less favorable on both the 44 and 5-7 structures. The strong CuxO <-> Cu interaction accompanied with the charge transfer from Cu to CuxO is able to stabilize the oxide film and hinder the removal of O. However, with the formation of more oxygen vacancies, the binding between CuxO and Cu(111) is weakened and the oxide film is destabilized, and Cu2O(111) is likely to become the most stable system under the reaction conditions. In addition, the surface defects also play an essential role. With the proceeding of the CO titration reaction, the 5-7 structure displays the highest activity among all three systems. Stone-Wales defects on the surface of the 5-7 structure exhibit a large difference from the 44 structure and Cu2O(111) in CO binding energy, stability of lattice oxygen, and, therefore, the reduction activity. The DFT results agree well with the experimental measurements, demonstrating that by adopting the unique conformation, the 5-7 structure is the active phase of CuxO, which is able to facilitate the redox reaction and the Cu2O/Cu(111)<-> Cu transition.

  • 4. Baber, Ashleigh E.
    et al.
    Xu, Fang
    Dvorak, Filip
    Mudiyanselage, Kumudu
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Senanayake, Sanjaya D.
    Sadowski, Jerzy T.
    Rodriguez, José A.
    Matolín, Vladimír
    White, Michael G.
    Stacchiola, Darío J.
    In Situ Imaging of Cu2O under Reducing Conditions: Formation of Metallic Fronts by Mass Transfer2013In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 45, p. 16781-16784Article in journal (Refereed)
    Abstract [en]

    Active catalytic sites have traditionally been analyzed based on static representations of surface structures and characterization of materials before or after reactions. We show here by a combination of in situ microscopy and spectroscopy techniques that, in the presence of reactants, an oxide catalyst's chemical state and morphology are dynamically modified. The reduction of Cu2O films is studied under ambient pressures (AP) of CO. The use of complementary techniques allows us to identify intermediate surface oxide phases and determine how reaction fronts propagate across the surface by massive mass transfer of Cu atoms released during the reduction of the oxide phase in the presence of CO. High resolution in situ imaging by AP scanning tunneling microscopy (AP-STM) shows that the reduction of the oxide films is initiated at defects both on step edges and the center of oxide terraces.

  • 5. Baber, Ashleigh E.
    et al.
    Yang, Xiaofang
    Kim, Hyun You
    Mudiyanselage, Kumudu
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Senanayake, Sanjaya D.
    Al-Mahboob, Abdullah
    Sadowski, Jerzy T.
    Evans, Jaime
    Rodriguez, Jose A.
    Liu, Ping
    Hoffmann, Friedrich M.
    Chen, Jingguang G.
    Stacchiola, Dario J.
    Stabilization of Catalytically Active Cu plus Surface Sites on TitaniumCopper Mixed-Oxide Films**2014In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 53, no 21, p. 5336-5340Article in journal (Refereed)
    Abstract [en]

    The oxidation of CO is the archetypal heterogeneous catalytic reaction and plays a central role in the advancement of fundamental studies, the control of automobile emissions, and industrial oxidation reactions. Copper-based catalysts were the first catalysts that were reported to enable the oxidation of CO at room temperature, but a lack of stability at the elevated reaction temperatures that are used in automobile catalytic converters, in particular the loss of the most reactive Cu+ cations, leads to their deactivation. Using a combined experimental and theoretical approach, it is shown how the incorporation of titanium cations in a Cu2O film leads to the formation of a stable mixed-metal oxide with a Cu+ terminated surface that is highly active for CO oxidation.

  • 6.
    Besharat, Zahra
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Halldin Stenlid, Joakim
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Soldemo, Markus
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Marks, Kess
    Önsten, Anneli
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Johnson, Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Öström, Henrik
    Weissenrieder, Jonas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Göthelid, Mats
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Dehydrogenation of methanol on Cu2O(100) and (111)2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, no 24Article in journal (Refereed)
    Abstract [en]

    Adsorption and desorption of methanol on the (111) and (100) surfaces of  Cu2O have been studied using high-resolution photoelectron spectroscopy in the temperature range 120–620 K, in combination with density functional theorycalculations and sum frequency generation spectroscopy. The bare (100) surfaceexhibits a (3,0; 1,1) reconstruction but restructures during the adsorption process into a Cu-dimer geometry stabilized by methoxy and hydrogen binding in Cu-bridge sites. During the restructuring process, oxygen atoms from the bulk that can host hydrogen appear on the surface. Heating transforms methoxy to formaldehyde, but further dehydrogenation is limited by the stability of the surface and the limited access to surface oxygen. The (√3 × √3)R30°-reconstructed (111) surface is based on ordered surface oxygen and copper ions and vacancies, which offers a palette of adsorption and reaction sites. Already at 140 K, a mixed layer of methoxy, formaldehyde, and CHxOy is formed. Heating to room temperature leaves OCH and CHx. Thus both CH-bond breaking and CO-scission are active on this  surface at low temperature. The higher ability to dehydrogenate methanol on (111) compared to (100) is explained by the multitude of adsorption sites and, in particular, the availability of surfaceoxygen.

  • 7. Evertsson, J.
    et al.
    Bertram, F.
    Zhang, Fan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Rullik, L.
    Merte, L. R.
    Shipilin, M.
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Ahmadi, Sareh
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Vinogradov, N.
    Carla, F.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Götelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Mikkelsen, A.
    Nilsson, J. -O
    Lundgren, E.
    The thickness of native oxides on aluminum alloys and single crystals2015In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 349, p. 826-832Article in journal (Refereed)
    Abstract [en]

    We present results from measurements of the native oxide film thickness on four different industrial aluminum alloys and three different aluminum single crystals. The thicknesses were determined using X-ray reflectivity, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. In addition, atomic force microscopy was used for micro-structural studies of the oxide surfaces. The reflectivity measurements were performed in ultra-high vacuum, vacuum, ambient, nitrogen and liquid water conditions. The results obtained using X-ray reflectivity and X-ray photoelectron spectroscopy demonstrate good agreement. However, the oxide thicknesses determined from the electrochemical impedance spectroscopy show a larger discrepancy from the above two methods. In the present contribution the reasons for this discrepancy are discussed. We also address the effect of the substrate type and the presence of water on the resultant oxide thickness.

  • 8. Fashandi, Hossein
    et al.
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Weissenrieder, Jonas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Gothelid, Mats
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Eriksson, Jens
    Eklund, Per
    Spetz, Anita Lloyd
    Andersson, Mike
    Applicability of MOS structures in monitoring catalytic properties, as exemplified for monolayer-iron-oxide-coated porous platinum films2016In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 344, p. 583-590Article in journal (Refereed)
    Abstract [en]

    Metal Oxide Semiconductor (MOS) capacitor devices comprised of monolayer iron oxide-coated as well as non-coated polycrystalline Pt deposited on oxidized silicon carbide substrates have been fabricated and their usefulness as realistic model systems in catalyst studies development was evaluated. The CO oxidation characteristics of both iron oxide- and non-coated Pt catalysts were investigated using mass spectrometry, monitoring the carbon dioxide production rate for different combinations of carbon monoxide (CO) and oxygen concentrations at various temperatures. Additionally, the output capacitance of the MOS model catalysts was recorded for each individual CO oxidation activity. A low-temperature shift in CO oxidation characteristics for the monolayer-coated compared to the non-coated Pt catalysts was observed, similar to that previously reported for monolayer iron oxide grown on single-crystalline Pt substrates. A strong correlation between the output capacitance of the MOS structures and the CO oxidation characteristics was found for both monolayer- and non-coated model catalysts. Furthermore, the devices exhibit retained MOS electrical output and CO oxidation characteristics as well as an unaffected catalyst surface composition, as confirmed by photoelectron spectroscopy, even after 200 h of continuous model catalyst operation. In addition to the implications on practical applicability of monolayer iron oxide coating on widely used polycrystalline Pt films in real-world catalysts and sensors, the findings also point to new possibilities regarding the use of MOS model systems for in situ characterization, high throughput screening, and tailoring of e.g. catalyst- and fuel-cell-electrode materials for specific applications.

  • 9.
    Ghadami Yazdi, Milad
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Lousada, Claudio M.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Evertsson, J.
    Rullik, L.
    Soldemo, Markus
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Bertram, F.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Weissenrieder, J.
    Lundgren, E.
    Göthelid, Mats
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Structure dependent effect of silicon on the oxidation of Al(111) and Al(100)2019In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 684, p. 1-11Article in journal (Refereed)
    Abstract [en]

    The effect of sub-monolayer silicon on the oxidation of Al(111) and Al(100) surfaces was investigated using X-ray Photoelectron Spectroscopy (XPS) and density functional theory (DFT) calculations. On both surfaces the adatom site is preferred over substituting Si into the Al-lattice; on Al(100) the four fold hollow site is vastly favored whereas on Al(111) bridge and hollow sites are almost equal in energy. Upon O 2 exposure, Si is not oxidized but buried at the metal/oxide interface under the growing aluminum oxide. On Al(111), Si has a catalytic effect on both the initial oxidation by aiding in creating a higher local oxygen coverage in the early stages of oxidation and, in particular, at higher oxide coverages by facilitating lifting Al from the metal into the oxide. The final oxide, as measured from the Al2p intensity, is 25–30% thicker with Si than without. This observation is valid for both 0.1 monolayer (ML) and 0.3 ML Si coverage. On Al(100), on the other hand, at 0.16 ML Si coverage, the initial oxidation is faster than for the bare surface due to Si island edges being active in the oxide growth. At 0.5 ML Si coverage the oxidation is slower, as the islands coalesce and he amount of edges reduces. Upon oxide formation the effect of Si vanishes as it is overgrown by Al 2 O 3 , and the oxide thickness is only 6% higher than on bare Al(100), for both Si coverages studied. Our findings indicate that, in addition to a vanishing oxygen adsorption energy and Mott potential, a detailed picture of atom exchange and transport at the metal/oxide interface has to be taken into account to explain the limiting oxide thickness.

  • 10.
    Grinter, David
    et al.
    Brookhaven Natl Lab, Chem, Ridge, NY USA..
    Luo, Si
    Brookhaven Natl Lab, Chem, Ridge, NY USA.;SUNY Stony Brook, Chem, Stony Brook, NY 11794 USA..
    Soldemo, Markus
    KTH.
    Piazza, Luca
    KTH.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Senanayake, Sanjaya
    Brookhaven Natl Lab, Chem, Ridge, NY USA..
    Stacchiola, Dario
    Brookhaven Natl Lab, Chem, Ridge, NY USA..
    Rodriguez, Jose
    Brookhaven Natl Lab, Chem, Ridge, NY USA.;SUNY Stony Brook, Chem, Stony Brook, NY 11794 USA..
    Potassium promotion of a model Au/TiO2 catalyst2016In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 252Article in journal (Other academic)
  • 11.
    Gustafsson, Oscar
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Karim, Amir
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Wang, Qin
    Reuterskiöld-Hedlund, Carl
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Ernerheim-Jokumsen, Christopher
    KTH.
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Persson, Sirpa
    Almqvist, Susanne
    Ekenberg, Ulf
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Noharet, Bertrand
    Asplund, Carl
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Andersson, Jan Y.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Photoluminescence and photoresponse from InSb/InAs-based quantum dot structures2012In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 19, p. 21264-21271Article in journal (Refereed)
    Abstract [en]

    InSb-based quantum dots grown by metal-organic vapor-phase epitaxy (MOVPE) on InAs substrates are studied for use as the active material in interband photon detectors. Long-wavelength infrared (LWIR) photoluminescence is demonstrated with peak emission at 8.5 mu m and photoresponse, interpreted to originate from type-II interband transitions in a p-i-n photodiode, was measured up to 6 mu m, both at 80 K. The possibilities and benefits of operation in the LWIR range (8-12 mu m) are discussed and the results suggest that InSb-based quantum dot structures can be suitable candidates for photon detection in the LWIR regime.

  • 12.
    Halldin Stenlid, Joakim
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Johansson, A. J.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Götelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Reactivity at the Cu2O(100):Cu-H2O interface: a combined DFT and PES study2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 44, p. 30570-30584Article in journal (Refereed)
    Abstract [en]

    The water-cuprite interface plays an important role in dictating surface related properties. This not only applies to the oxide, but also to metallic copper, which is covered by an oxide film under typical operational conditions. In order to extend the currently scarce knowledge of the details of the water-oxide interplay, water interactions and reactions on a common Cu2O(100):Cu surface have been studied using high-resolution photoelectron spectroscopy (PES) as well as Hubbard U and dispersion corrected density functional theory (PBE-D3+U) calculations up to a bilayer water coverage. The PBE-D3+U results are compared with PBE, PBE-D3 and hybrid HSE06-D3 calculation results. Both computational and experimental results support a thermodynamically favored, and H2O coverage independent, surface OH coverage of 0.25-0.5 ML, which is larger than the previously reported value. The computations indicate that the results are consistent also for ambient temperatures under wet/humid and oxygen lean conditions. In addition, both DFT and PES results indicate that the initial (3,0; 1,1) surface reconstruction is lifted upon water adsorption to form an unreconstructed (1 x 1) Cu2O(100) structure.

  • 13. Martynova, Y.
    et al.
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Sachert, S.
    Polzin, S.
    Widdra, W.
    Shaikhutdinov, S.
    Freund, H. -J
    CO Oxidation Over Monolayer Manganese Oxide Films on Pt(111)2013In: Catalysis Letters, ISSN 1011-372X, E-ISSN 1572-879X, Vol. 143, no 11, p. 1108-1115Article in journal (Refereed)
    Abstract [en]

    Ultrathin manganese oxide films grown on Pt(111) were examined in the low temperature CO oxidation reaction at near atmospheric pressures. Structural characterization was performed by X-ray photoelectron spectroscopy, Auger electron spectroscopy, high-resolution electron energy loss spectroscopy, and temperature programmed desorption. The results show that the reactivity of MnOx ultrathin films is governed by a weakly bonded oxygen species, which may even be formed at low oxygen pressures (similar to 10(-6) mbar). For stable catalytic performance at realistic conditions the films required highly oxidizing conditions (CO:O-2 < 1:10), otherwise the films dewetted, ultimately resulting in the catalyst deactivation. Comparison with other thin films on Pt(111) shows, that the desorption temperature of weakly bonded oxygen species can be used as a benchmark for its activity in this reaction.

  • 14.
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Transition metal oxide surfaces: Surface structures and molecular interaction2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Metal oxides are both corrosion products and useful materials with a wide range of applications. Two of the most used metals today are iron and copper. In this thesis, surface structures and molecular interaction with surfaces of iron oxides and copper oxides are studied using spectroscopy and microscopy methods.

     

    The surface structures of iron oxides grown on the low-index iron (Fe) surfaces (100) and (110) have been studied during the initial oxidation phase. The oxidation condition for both iron surfaces was 400 °C and 1×10−6 mbar of oxygen gas. For the Fe(100)-surface, a Fe3O4(100)-film is formed beyond the oxygen adsorbate structures. For the Fe(110)-surface, a FeO(111)-film is first formed. When the FeO(111)-film grows thicker, it transforms into a Fe3O4(111)-film.

     

    The surface structures of Cu2O(100) was studied and the main finding is that the most common surface structure that previously in literature has been described to have a periodicity of (3√2×√2)R45° actually has a periodicity described by the matrix (3,0;1,1). Furthermore, the low-binding energy component in the photoelectron spectroscopy O 1s-spectrum is determined to origin from surface oxygen atoms.

     

    Sulfur dioxide, a corrosive molecule that in the environment to large share comes from human activities such as burning of fossil fuels, was studied using photoelectron spectroscopy when interacting with surfaces of iron oxide thin films and bulk Cu2O-surfaces. On the iron oxide thin film surfaces under ultra-high vacuum conditions, sulfur dioxide adsorbs partly as SO4-species and partly dissociates and forms FeS2. On the Cu2O-surfaces under ultra-high vacuum conditions, the adsorption of sulfur dioxide is non-dissociative and forms SO3-species. When interacting with near-ambient pressures of water, it is observed in the photoelectron spectroscopy S 2p-region that the sulfur from SO3-species shifts to Cu2S.

  • 15.
    Soldemo, Markus
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Halldin Stenlid, Joakim
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Besharat, Zahra
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Ghadami Yazdi, Milad
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Önsten, Anneli
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    The Surface Structure of Cu2O(100)2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 8, p. 4373-4381Article in journal (Refereed)
    Abstract [en]

    Despite the industrial importance of copper oxides, the nature of the (100) surface of Cu2O has remained poorly understood. The surface has previously been subject to several theoretical and experimental studies, but has until now not been investigated by atomically resolved microscopy or high-resolution photoelectron spectroscopy. Here we determine the atomic structure and electronic properties of Cu2O(100) by a combination of multiple experimental techniques and simulations within the framework of density functional theory (DFT). Low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) characterized the three ordered surface structures found. From DFT calculations, the structures are found to be energetically ordered as (3,0;1,1), c(2 x 2), and (1 x 1) under ultrahigh vacuum conditions. Increased oxygen pressures induce the formation of an oxygen terminated (1 x 1) surface structure. The most common termination of Cu2O(100) has previously been described by a (3 root 2 x root 2)R45 degrees unit cell exhibiting a LEED pattern with several missing spots. Through atomically resolved STM, we show that this structure instead is described by the matrix (3,0;1,1). Both simulated STM images and calculated photoemission core level shifts compare favorably with the experimental results.

  • 16.
    Soldemo, Markus
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Johansson, Niclas
    Besharat, Zahra
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Önsten, Anneli
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Knudsen, Jan
    Schnadt, Joachim
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Cuprous oxide surfaces exposed to sulfur dioxide and near-ambient pressures of waterManuscript (preprint) (Other academic)
    Abstract [en]

    The interaction of sulfur dioxide with Cu2O(100) and Cu2O(111) at ultra-high vac-uum is studied. It is found that on both surfaces, the sulfur dioxide moleculesbind as SO3-species. Dosing water in UHV does not impact the SO3-species at thedoses used. When dosing water at near-ambient pressure conditions, however, itis observed that the sulfur in the SO3-species shifts to Cu2S when monitoring thePES S 2p-region.

  • 17.
    Soldemo, Markus
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Jonas, Weissenrieder
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Oxidation of Fe(100) in oxygen gas at 400 °CManuscript (preprint) (Other academic)
    Abstract [en]

    The oxidation of Fe(100) was studied at an oxygen gas pressure of 1×10−6mbarand a temperature of 400°C. The main findings is that the oxide film, beyond oxy-gen adsorbate structure, is formed by layer-by-layer growth and has a Fe3O4(100)termination.

  • 18.
    Soldemo, Markus
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Lundgren, E.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Oxidation of Fe(110) in oxygen gas at 400 °c2016In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 644, p. 172-179Article in journal (Refereed)
    Abstract [en]

    The initial oxidation of Fe(110) in oxygen gas at 400 °C beyond initial adsorbate structures has been studied using X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, low-energy electron diffraction, and scanning tunneling microscopy (STM). Formation of several ordered phases of surface oxides is observed at oxygen coverages between approximately 2.3 and 3.5 oxygen atoms/Fe(110) surface atom. Initially, a FeO(111)-like film is formed with a parallelogram-shaped moiré pattern. It has two mirror domains that are formed symmetrically around the growth direction of a zigzag-shaped adsorbate structure. With increased local oxygen coverage, the moiré structure transforms into a ball-shaped form. Both these moiré structures have equal atomic stacking at the surface and equal apparent height in STM, suggesting oxygen ions diffusing into the film upon oxidation and that the oxide growth takes place at the iron-iron oxide interface. The FeO(111)-like film turns into a Fe3O4(111)-like film with a triangular bistable surface termination as the oxidation proceeds further. The FeO(111)-like film growth proceeds according to the Frank-van der Merwe mechanism while the Fe3O4(111)-like film grows according to the Stranski-Krastanov mechanism.

  • 19.
    Soldemo, Markus
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Niu, Yuran
    Zakharov, Alexei
    Lundgren, Edvin
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    A well-ordered surface oxide on Fe(110)2015In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 639, p. 13-19Article in journal (Refereed)
    Abstract [en]

    A well-ordered surface oxide grown on Fe(110) has been studied using scanning tunneling microscopy (STM), low energy electron diffraction, low energy electron microscopy, and core level photoelectron spectroscopy. The iron oxide film exhibits wide terraces and is formed after exposure to 100-1000 L at 1 x 10(-6) mbar O-2 and 400 degrees C. Two domains, mirror symmetric in the Fe(110)-lattice mirror symmetry planes but otherwise equal, are observed. The surface oxide forms a relatively large coincidence surface unit cell (16.1 angstrom x 26.5 angstrom). Imaging by STM reveals a strong bias dependence in the apparent height within the surface unit cell. The oxygen terminating atomic layer has a hexagonal atomic structure, FeO(111)-like, with the atomic sparing of 3.2 angstrom, that is expanded by similar to 63% relative to bulk FeO(111).

  • 20.
    Soldemo, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Vandichel, Matthias
    Chalmers Univ Technol, Dept Phys, SE-41296 Gothenburg, Sweden.;Chalmers Univ Technol, Competence Ctr Catalysis, SE-41296 Gothenburg, Sweden.;Aalto Univ, Dept Chem & Mat Sci, Sch Chem Engn, Sch Sci, Espoo 02150, Finland.;Aalto Univ, Dept Appl Phys, Sch Chem Engn, Sch Sci, Espoo 02150, Finland..
    Gronbeck, Henrik
    Chalmers Univ Technol, Dept Phys, SE-41296 Gothenburg, Sweden.;Chalmers Univ Technol, Competence Ctr Catalysis, SE-41296 Gothenburg, Sweden..
    Weissenrieder, Jonas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Initial Fe3O4(100) Formation on Fe(100)2019In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 26, p. 16317-16325Article in journal (Refereed)
    Abstract [en]

    The initial oxidation of Fe(100) at 400 degrees C has been studied by X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), and low-energy electron diffraction, in combination with density functional theory calculations. The first observed well-ordered surface oxide is formed at a coverage of similar to 3 oxygen atoms per unreconstructed surface Fe(100) atom. STM shows that this surface oxide is terminated by straight atomic rows exhibiting a p(2 X 1) periodicity. However, already for oxide films with a coverage of similar to 4 oxygen atoms (corresponding to one Fe3O4 unit cell thickness), wiggly atomic rows appear similar to the c(2 X 2) reconstructed Fe3O4 (100)-surface with the Fe3O4 unit vectors rotated 45 degrees to Fe(100). The wiggly rows are a consequence of subsurface cation iron vacancies, which previously have been observed for bulk surfaces. The formation of subsurface vacancies is supported by the XPS O is signature, which is modeled by considering the core-level shifts for all oxygen atoms in the film. Throughout the oxidation series, the microscopy results reveal a layer-by-layer (Frank-van der Merwe) growth.

  • 21.
    Soldemo, Markus
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Sulfur dioxide interaction with oxidized low-index iron surfacesManuscript (preprint) (Other academic)
    Abstract [en]

    Sulfur dioxide was dosed on thin iron oxides grown on Fe(100) and Fe(110) (fromPaper 1 and Paper 2). It is found that the sulfur dioxide molecules adsorb as SO4-species at room temperature and that some of the adsorbed molecules dissociateupon adsorption and forming FeS2. The oxides corresponding to the lowest dosesof oxygen gas in Paper 1 and Paper 2 were annealed after the sulfur dioxide dos-ing, resulting in increased amount of dissociated molecules. The thicker oxides, onboth surfaces were exposed to another dose of sulfur dioxide, the change of sulfurcoverages show that the surfaces are almost saturated.

  • 22. Xu, Fang
    et al.
    Mudiyanselage, Kumudu
    Baber, Ashleigh E.
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    White, Michael G.
    Stacchiola, Dario J.
    Redox-Mediated Reconstruction of Copper during Carbon Monoxide Oxidation2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 29, p. 15902-15909Article in journal (Refereed)
    Abstract [en]

    Copper has excellent initial activity for the oxidation of CO, yet it rapidly deactivates under reaction conditions. In an effort to obtain a full picture of the dynamic morphological and chemical changes occurring on the surface of catalysts under CO oxidation conditions, a complementary set of in situ ambient pressure (AP) techniques that include scanning tunneling microscopy, infrared reflection absorption spectroscopy (IRRAS), and X-ray photoelectron spectroscopy were conducted. Herein, we report in situ AP CO oxidation experiments over Cu(111) model catalysts at room temperature. Depending on the CO:O-2 ratio, Cu presents different oxidation states, leading to the coexistence of several phases. During CO oxidation, a redox cycle is observed on the substrate's surface, in which Cu atoms are oxidized and pulled from terraces and step edges and then are reduced and rejoin nearby step edges. IRRAS results confirm the presence of under-coordinated Cu atoms during the reaction. By using control experiments to isolate individual phases, it is shown that the rate for CO oxidation decreases systematically as metallic copper is fully oxidized.

  • 23.
    Zabel, Thomas
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Reuterskiöld Hedlund, Carl
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Gustafsson, O.
    Karim, A.
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Wang, Q.
    Ernerheim Jokumsen, Christopher
    KTH, School of Information and Communication Technology (ICT).
    Soldemo, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Gotelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Auger recombination in In(Ga)Sb/InAs quantum dots2015In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 106, no 1, p. 013103-Article in journal (Refereed)
    Abstract [en]

    We report on the epitaxial formation of type II In0.5Ga0.5Sb/InAs and InSb/InAs quantum dot ensembles using metal organic vapor phase epitaxy. Employing scanning tunneling spectroscopy, we determine spatial quantum dot dimensions smaller than the de Broglie wavelength of InGaSb, which strongly indicates a three dimensional hole confinement. Photoluminescence spectroscopy at low temperatures yields an enhanced radiative recombination in the mid-infrared regime at energies of 170-200 meV. This luminescence displays a strong excitation power dependence with a blueshift indicating a filling of excited quantum dot hole states. Furthermore, a rate equation model is used to extract the Auger recombination coefficient from the power dependent intensity at 77 K yielding values of 1.35 x 10(-28) cm(6)/s for In0.5Ga0.5Sb/InAs quantum dots and 1.47 x 10(-27) cm(6)/s for InSb/InAs quantum dots, which is about one order of magnitude lower as previously obtained values for InGaSb superlattices.

1 - 23 of 23
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