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  • 101.
    Roseborough, Diana
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    The surface behavior of mercury on iron systems2006In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 6, p. 1049-1056Article in journal (Refereed)
    Abstract [en]

    Thermal desorption Auger electron spectroscopy (TDAES) was used to investigate the circumstances under which mercury is adsorbed on the surface of iron in the temperature interval of 85 to 298 K. The effects of chlorine and oxygen modifications on the iron surface have also been investigated within the same temperature interval. It was seen that chlorine reduced the adsorption of mercury on polycrystalline iron at 85 K, as did oxygen. On the clean iron system at 298 K, only one monolayer (ML) of mercury adsorbed. The physisorption of mercury on chlorine and oxygen layers at low temperatures (LTs) is discussed in combination with the calculated activation energies of desorption, as well as the factors affecting the mechanism of adsorption at room temperature.

  • 102.
    Roseborough, Diana
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Palmgren, P.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Surface chemistry of mercury on zinc and copper2006In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 6, p. 1057-1066Article in journal (Refereed)
    Abstract [en]

    Thermal desorption Auger electron spectroscopy (TDAES) was used to investigate mercury adsorption on the surfaces of zinc (Zn) and copper (Cu) in the temperature interval of 85 to 298 K. The effects of chlorine and oxygen modifications on the surfaces have also been investigated within the same temperature interval. On single crystalline Zn(0001), no mercury was adsorbed under any temperature or deposition conditions. On polycrystalline Zn at 85 K, a monolayer (ML) of mercury adsorbed, whereas no measurable quantity was observed at room temperature (RT). Predeposited chlorine was removed by exposure to mercury, most probably through formation of volatile HgCl2. Chlorine enhanced the adsorption of mercury on polycrystalline Cu at 87 K, whereas preoxidation reduced the coverage. Low temperatures (LTs) were conducive to mercury adsorption as compared to 298 K for the Cu systems studied. The physisorption of mercury on chlorine and oxygen layers at LTs is discussed, as well as the factors affecting the mechanism of adsorption at RTs. The desorption energies and surface enthalpies have been calculated for each system with mercury adsorption.

  • 103. Rutishauser, Simon
    et al.
    Zanette, Irene
    Donath, Tilman
    Sahlholm, Anna
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    David, Christian
    Structured scintillator for hard x-ray grating interferometry2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 17, p. 171107-Article in journal (Refereed)
    Abstract [en]

    Grating interferometry at conventional x-ray tubes improves the quality of radiographies and tomograms by providing phase and scattering contrast data. The main challenge encountered when applying this technique at high photon energies, as required by many applications to obtain sufficient penetration depth, is to maintain a high fringe visibility. In this letter, we report on a substantial improvement in fringe visibility and according improvements in image quality achieved by replacing the absorbing analyzer grating of the interferometer with a structured scintillator grating. This development represents a significant step toward the implementation of this technique in industrial testing and medical applications.

  • 104.
    Sangghaleh, Fatemeh
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Bruhn, Benjamin
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Schmidt, Torsten
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Exciton lifetime measurementson single silicon quantum dots: explanation of stretched exponentialdecay2011Manuscript (preprint) (Other academic)
  • 105.
    Sani, Sohrab R
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Persson, J.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Mohseni, S. M.
    Fallahi, Vahid
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    Current induced vortices in multi-nanocontact spin-torque devices2011In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 109, no 7, p. 07C913-Article in journal (Refereed)
    Abstract [en]

    We demonstrate spin transfer torque (STT) switching in multi-nanocontact STT devices fabricated using hole mask colloidal lithography. We also study the STT device resistance and switching properties as a function of applied magnetic field and nanocontact current. At low nanocontact current, magnetoresistance measurements show sharp, single-step switching at low switching fields. When the current is increased, the switching becomes multistep, and the switching field increases dramatically. We explain these results as arising from a transition from a predominantly single domain like switching to switching involving a vortex state. Micromagnetic simulations corroborate this picture, indicating that a single magnetic vortex nucleates in between the nanocontacts through the influence from the total Oersted field generated by the nanocontact ensemble.

  • 106.
    Sani, Sohrab R.
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Persson, Johan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Dmitriev, Alexander
    Kall, Mikael
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Hole mask colloidal lithography on magnetic multilayers for spin torque applications2010In: INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009) / [ed] Goll, G; Lohneysen, HV; Loidl, A; Pruschke, T; Richter, M; Schultz, L; Surgers, C; Wosnitza, J, BRISTOL: IOP PUBLISHING LTD, DIRAC HOUSE , 2010, Vol. 200, p. UNSP 072078-Conference paper (Refereed)
    Abstract [en]

    We demonstrate the fabrication of metallic nano-contacts on magnetic multilayers using a Hole Mask Colloidal Lithography technique (HCL) based on Polystyrene spheres. The method applies PMMA as a sacrificial layer upon which a hole pattern is formed after liftoff of the spheres. An Au layer functions as a hard mask for the PMMA and the PMMA subsequently masks the SiO(2) during its etching. The resulting pattern is a dense collection of randomly located nano-holes through a SiO(2) film. Final devices are made using traditional photolithography to define a 600 nm circular mesa with about 3 to 4 nano-holes per device, and patterning of a metallic top contact.

  • 107.
    Schmidt, Torsten
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Chizhik, A. I.
    Chizhik, A. M.
    Potrick, K.
    Meixner, A. J.
    Huisken, F.
    Radiative exciton recombination and defect luminescence observed in single silicon nanocrystals2012In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, no 12, p. 125302-Article in journal (Refereed)
    Abstract [en]

    The role of quantum confinement (QC) and surface-related defect centers (DCs) on the photoluminescence (PL) of individual silicon nanocrystals (Si NCs) is investigated using confocal microscopy with radially and azimuthally polarized laser beams. It is shown that the multiple-peak PL spectra of single Si NCs revealing SiO 2 phonon side bands are associated with a linear transition dipole moment (TDM) and a short lifetime of 4 ns, indicating that the PL originates from defect centers. In a new study applied to free-standing single Si NCs obtained by Si cluster beam deposition, we could discriminate between PL centers with one- and more-dimensional TDM. Nanoparticles revealing a three-dimensional TDM are characterized by a significantly weaker and structureless Gaussian PL band at larger wavelengths and by ÎŒs lifetimes. These PL features are attributed to the radiative recombination of quantum-confined excitons generated in the Si cores. Within the same sample, we found coexistence of Si NCs exhibiting QC PL and others showing DC PL.

  • 108.
    Shamsa, Arya
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Computerized data analysis of numerous spectra fromindividual quantum dots: Identifying Quantum-dot signals by Image-processing2012Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    In this work an image processing software was developed to extract single nanocrystals luminescence spectra from spectral images containing various noises and parasitic signals. This software helps users to process and analyze experimental data in a simplified and intuitive way and allows quick analysis of large volumes of data. The output results are the distributions of peak emission energy and inter-peak spacing. The software also generates text-files containing the extracted information for further analysis. Also experimental photoluminescence measurements have been performed at liquid nitrogen temperature of 77K, on phosphorous doped silicon nanocrystals. The data were analyzed with the developed software and with other data confirm previous results indicating the accuracy of the methodology used in the code. The implementation of this software for data analysis can process information without human bias and hopefully find hidden patterns that previously been lost when analyzing data manually.

  • 109. Shariati, Masumeh-Nina
    et al.
    Luder, Johann
    Bidermane, Ieva
    Ahmadi, Sareh
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Göthelid, Emmanuelle
    Palmgren, Pål
    Sanyal, Biplab
    Eriksson, Olle
    Piancastelli, Maria Novella
    Brena, Barbara
    Puglia, Carla
    Photoelectron and Absorption Spectroscopy Studies of Metal-Free Phthalocyanine on Au(111): Experiment and Theory2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 14, p. 7018-7025Article in journal (Refereed)
    Abstract [en]

    The adsorption of monolayers and multilayers of metal-free phthalocyanine molecules on the Au(111) (root 3 x 22) reconstructed surface has been investigated by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). Our results for the monolayer show that the molecules are arranged tightly onto the surface with their molecular plane parallel to it. In addition, the X-ray absorption spectra of the monolayer have been modeled by density functional theory, which could enlighten new aspect of the interaction between molecules and substrate. The XAS results evidence that also in the multilayer the molecules keep the orientation with the molecular plane parallel to the surface. These results are discussed in the framework of moleculemolecule/moleculeadsorbate interactions.

  • 110. Shkar, V. F.
    et al.
    Nikolaev, E. I.
    Sayapin, V. N.
    Linnik, A. I.
    Denysenkov, V. P.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Khartsev, Sergiy
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Structure and properties of deposited yttrium iron garnet films2005In: Physics of the solid state, ISSN 1063-7834, E-ISSN 1090-6460, Vol. 47, no 6, p. 1107-1110Article in journal (Refereed)
    Abstract [en]

    Ferromagnetic resonance (FMR) and vibrating-sample magnetometer techniques were used to study the nature of the structural characteristics of yttrium iron garnet films deposited through either liquid phase epitaxy or laser evaporation on a (111)-oriented gallium gadolinium garnet substrate. It was proved that, based on the experimentally observed cubic magnetic anisotropy, deposited films should be considered to be single crystals. However, the absence of the FMR domain branch in a nonsaturated film and the shape of the magnetization curve indicate that a deposited film when demagnetized does not have a domain structure, as would be expected for a single-crystal film. According to the model proposed, a deposited film consists of close-packed single-crystal fragments with equal crystallographic orientation, the boundaries between which are in a partially atomically disordered state. As a result, such a film is both locally and macroscopically anisotropic, like a continuous single crystal. This film can split into domains only within a fragment (as is the case in a magnetic granular polycrystal); however, this does not happen, because the linear dimensions of a submicroscopic fragment are smaller than the equilibrium domain width.

  • 111. Stoltz, D.
    et al.
    Bielmann, M.
    Schlapbach, L.
    Bovet, M.
    Berger, H.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Stoltz, S. E.
    Starnberg, H. I.
    Atomic origin of the scanning tunneling microscopy images of charge-density-waves on 1T-TaSe22008In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 403, no 13-16, p. 2207-2210Article in journal (Refereed)
    Abstract [en]

    We show atomically resolved scanning tunneling microscopy (STM) images of charge density waves (CDWs) at room temperature together with angle-resolved photoelectron band-mapping of 1T-TaSe2. By comparing the results of these two techniques, we demonstrate the atomic structure of the CDW-features observed by the STM and atomic origin of the reconstructed band-structure in this material.

  • 112.
    Stoltz, Dunja
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Önsten, Anneli
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    High resolution spectroscopic and microscopic signatures of ordered growth of ferrous sulfate in SO2 assisted corrosion of Fe3O4(100)2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 9Article in journal (Refereed)
    Abstract [en]

    The authors present a high-resolution core-level photoemission study of a Fe3O4(100) surface exposed to 50 L (1 L=10(-6) mbar s) of H2O and 50 L of SO2. S 2p core-level spectra reveal the presence of SO3 and SO4 species. An additional peak in the Fe 3p core-level spectrum shows that they bond with iron from the substrate. Complementary scanning tunneling microscopy of the same surface demonstrates formation of a long-range ordered sulfate locked in the (root 2x root 2)R45 degrees-surface potential.

  • 113.
    Stoltz, Dunja
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Önsten, Anneli
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Scanning tunneling microscopy of Fe- and O-sublattices on Fe3O4(100)2008In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 108, no 6, p. 540-544Article in journal (Refereed)
    Abstract [en]

    We present scanning tunneling microscopy of an octahedral (B) plane terminated (root 2 x root 2)R45 degrees-reconstructed surface of a natural magnetite (10 0) crystal. Implementing a W-tip we achieve the same resolution on Fe rows as was reported in the past either with the use of antiferromagnetic tips or on magnetite (Fe3O4) films. We show images of Fe or O sublattices of Fe3O4 with atomic resolution.

  • 114. Suchodolskis, A.
    et al.
    Assmus, W.
    Babonas, G. J.
    Giovanelli, L.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Karpus, V.
    Le Lay, G.
    Reza, A.
    Uhrig, E.
    Photoemission and optical spectroscopy of i-ZnMgEr quasicrystal2005In: Acta Physica Polonica. A, ISSN 0587-4246, E-ISSN 1898-794X, Vol. 107, no 2, p. 412-419Article in journal (Refereed)
    Abstract [en]

    The results of photoemission and optical studies of icosahedral single-grain ZnMgEr quasicrystals are presented. Synchrotron radiation photoemission measurements were performed on in situ cleaved samples at 10(-10) mbar pressure and low, 140-150 K temperature. The valence band photoemission spectra measured reveal a simple metal-type valence band of icosahedral ZnMgEr with a distinct Fermi edge cut-off and with a sharp pseudogap feature. The photoemission spectra of shallow Mg 2p and Zn 3d core levels indicate a coordination shift of Mg 2p spin-orbit doublet and an oscillating dependence of Zn 3d photoemission line components on the photon energy within the hv = 20-160 eV range investigated. The optical response of icosahedral ZnMgEr, a dispersion of the dielectric function, was measured by the spectroscopic ellipsometry technique in the 0.5-5.0 eV spectral range. The optical spectra of the quasicrystal indicate the Drude-type optical response superimposed with a peak of interband optical transitions. The interband optical transitions can be modelled with the pseudogap parameters which agree with those deduced in an analysis of the photoemission valence band spectra.

  • 115.
    Sychugov, Ilya
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Optical Properties of a Silicon Nanocrystal2009In: Nanocrystals: Properties, Preparation and Applications / [ed] Hongquig Hu, New York: Nova Science , 2009, p. 197-216Chapter in book (Refereed)
    Abstract [en]

    Basic optical properties of a silicon nanocrystal are discussed based on results from single-dot spectroscopy experiments. Luminescence linewidth and its temperature behavior, time dependency of the intensity trace and strong variations from dot-to-dot are particularly addressed. It appears that the fundamental optical features of a silicon nanocrystal are similar to that of its direct bandgap semiconductor counterpart, while in general preserving the indirect bandgap structure of bulk silicon. One of possible ways to modify its characteristics is to alter the local density of optical modes (LDOS) around this nano-emitter. The influence of LDOS is discussed based on experimental observations of substrate proximity and photonic bandgap effects. It is shown how the silicon nanocrystal excitation lifetime, luminescence yield and quantum efficiency can be modified in this way. By proper ‘nano-engineering’ this may lead to enhanced radiative properties useful for future applications.

  • 116.
    Sychugov, Ilya
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Valenta, J.
    Mitsuishi, K.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Exciton localization in doped Si nanocrystals from single dot spectroscopy studies2012In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, no 7, p. 075311-Article in journal (Refereed)
    Abstract [en]

    The results of low-temperature photoluminescence characterization of single silicon nanocrystals prepared from highly doped silicon-on-insulatorwafers are presented. The effect of B, P, As, and Sb impurities on ensemble as well as individual emission spectra are determined by comparison with the line shapes of undoped nanocrystals. From the statistical analysis of the luminescence spectra, the donor ionization energies for nanocrystals emitting in the range of 1.5-2.0 eV are estimated to be 140-200 meV, while the exciton-impurity binding energy for As- and Sb-doped nanocrystals is found to be about 40-45 meV.

  • 117.
    Szamota-Leandersson, Karolina
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Electronic structure of clean and adsorbate-covered InAs surfaces2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is the result of investigations regarding the processes in InAs III-V semiconductor surfaces induced by additional charge incorporated by adsorbates. The aim of the project is to study the development of the accumulation layer on the metal/InAs(111)A/B surfaces and its electronic structure. InAs(111)A is indium-terminated and InAs(111)B is arsenic-terminated. In addition, InAs(100) is also studied. These three substrates are different; InAs(111)A has a (2x2)-termination, explained by an indium vacancy model, and the clean surface exhibits a two-dimensional electron gas (2DEG). InAs(111)B(1x1) is bulk-truncated and unreconstructed and does not host a 2DEG. InAs(100)(4x2)/c(8x2) exhibits a more covalent character of the surface bonds compared to InAs(111)A/B, and the surface is terminated by a complex reconstruction. Photoelectron spectroscopy and LEED (low energy electron diffraction) have been used as the main tools to study surfaces with sub-monolayer to monolayer amounts of adsorbates. A photoemission peak related to a two-dimensional electron gas appears close to the Fermi level. This 2DEG has in most cases InAs bulk properties, since it is located in the InAs conduction band. A systematic study of core levels and valence bands reveals that the appearance of the 2DEGs is a complex process connected to the surface order. Adsorption of lead, tin or bismuth on InAs(111)B(1x1) induces emission from a 2DEG, but only at monolayer coverage and when the surface is ordered. Cobalt reacts strongly with InAs forming InCo islands and no accumulation is observed.

    Examination of Cs/InAs(111)B does not reveal any 2DEG and the surface reaction is strongly related to the clean surface stabilization process. Examination of the In-terminated InAs(111)A(2x2) surface shows that In reacts strongly with cobalt and tin adatoms and with oxygen in cases of large exposure, which decreases the 2DEG intensity, while adatoms of cesium and small doses of oxygen enhance the emission from the 2DEG. InAs(100) is terminated with one kind of atom - the InAs(100)(4x2)/c(8x2) is indium terminated. Bismuth creates dimers on the surface and a 2DEG is observed.

    More generally, this thesis describes some of the general physical background applied to surface science and 2DEG. The first part is a general overview of the processes on the surface. The second part concentrates on the methods related to preparation of samples, and the third part on the measurement methods. The photoelectron spectroscopy part concerns the theory used in mapping electronic structure. The inserted figures are taken from different experiments, including results for InAs(111)A not previously published.

     

     

  • 118.
    Szamota-Leandersson, Karolina
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Bugoi, R.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Le Lay, G.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Pb induced charge accumulation on InAs(111)B2007In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 601, no 15, p. 3246-3252Article in journal (Refereed)
    Abstract [en]

    The Pb/InAs(111)B interface has been studied by synchrotron radiation photoelectron spectroscopy (SR-PES) of valence band and ln4d, As3d and Pb5d core levels. Room temperature deposition of similar to 1 ML of Pb on InAs(I I I)B leads to an ordered overlayer that induces a metallic channel at the surface, as seen through a weak emission in the vicinity of the Fermi level. Its narrow localization in reciprocal space supports the formation of a two-dimensional free electron gas (2DEG) in the surface region. It is proposed that the adsorbed metal layer swaps the initial polarisation of the surface and thus pulls electrons back to the surface. This charge re-arrangement increases the charge density in the accumulation layer and reduces the screening length and thus the depth of the potential well at the surface.

  • 119.
    Szamota-Leandersson, Karolina
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Kanski, J.
    Ilver, L.
    Le Lay, G.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Creation of a metallic channel at the Sn/InAs(111)B surface studied using synchrotron-radiation photoelectron spectroscopy2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 205406Article in journal (Refereed)
    Abstract [en]

    The properties of a Sn-induced two-dimensional electron gas at the As-terminated InAs(111)B(1x1) surface was studied by synchrotron radiation photoelectron spectroscopy. The two-dimensional electron gas reveals itself via a narrow structure at the Fermi level, visible close to normal emission for tin coverage in the range 0.5 to 2 monolayers. Although this electron gas exhibits properties that in several respects resemble those of intrinsic charge accumulation layers on free InAs surfaces, our observations suggest that the present electron gas is much more linked to the Sn adlayer.

  • 120.
    Szamota-Leandersson, Karolina
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Leandersson, M.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Adsorption of Cs on InAs(111) surfaces2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 15, p. 5267-5270Article in journal (Refereed)
    Abstract [en]

    Caesiated InAs(111)B (1 x 1) and InAs(111)A (2 x 2) surfaces have been studied by photoelectron spectroscopy. On the InAs(111)B a new (root 3 x root 3)R30 degrees reconstruction was observed. During Cs evaporation remarkably small changes are observed in the lone pair states, and no sign of an accumulation layer at the surface can be observed. Instead, the additional charge provided by Cs is rapidly transported towards the bulk. On the InAs(111)A cesium behaves as a typical electropositive alkali metal donator that enhances the already existing accumulation layer.

  • 121. Tacchi, S.
    et al.
    Nguyen Thi Ngooc, Anh
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Carlotti, G.
    Gubbiotti, G.
    Madami, M.
    Dumas, R. K.
    Lau, J. W.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Rettori, A.
    Pini, M. G.
    Spin wave excitations in exchange-coupled [Co/Pd]-NiFe films with tunable tilting of the magnetization2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 14, p. 144426-Article in journal (Refereed)
    Abstract [en]

    Brillouin light scattering was applied to measure the evolution of spin waves in exchange-coupled [Co/Pd]-NiFe films with out-of-plane/in-plane magnetic anisotropy. Tunable tilting of the magnetization has important effects on the spin wave frequency gap: a substantial increase is observed with decreasing the soft NiFe thickness, while seemingly insignificant tilting angles cause a strong reduction with respect to a film with only the hard [Co/Pd] component. The spin wave frequency is reproduced also in samples, with increased thickness of the upper Pd layer, where a sudden modification in the tilting at the hard/soft interface is caused by the weakening of interlayer exchange.

  • 122. Tenga, A.
    et al.
    Garcia-Garcia, F. J.
    Mikhaylushkin, A. S.
    Espinosa-Arronte, B.
    Andersson, Magnus
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Haussermann, U.
    Sphalerite-chalcopyrite polymorphism in semimetallic ZnSnSb22005In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 17, no 24, p. 6080-6085Article in journal (Refereed)
    Abstract [en]

    We have investigated the system ZnSnSb2 in the course of our attempts to modify thermoelectric Zn-Sb frameworks. ZnSnSb2 is only accessible when employing Sn as reactive flux in the synthesis. The material shows an order-disorder transition in the temperature interval between 225 and 240 degrees C and decomposes peritectically at about 360 degrees C. The high-temperature form of ZnSnSb2 adopts the Zn/Sn disordered cubic sphalerite-type structure. Electron microscopy investigations reveal that samples quenched from 350 degrees C already contain domains of the low-temperature form, which has the Zn/Sn ordered tetragonal chalcopyrite structure. The c/a ratio of the tetragonal structure is, within experimental errors, identical to the ideal value 2. This gives rise to intricate microtwinning in the low-temperature chalcopyrite form of ZnSnSb2 as obtained in samples quenched from 250 degrees C. First principles electronic structure calculations demonstrate that the tetragonal low-temperature form of ZnSnSb2 has a narrow band gap of about 0.2 eV. This is in agreement with the semimetallic behavior of the material found from resistivity measurement. The shape of the electronic density of states for ZnSnSb2 is similar to thermoelectric binary Zn-Sb frameworks. However, the thermopower of ZnSnSb2 is rather low with room-temperature values ranging from 10 to 30,mu V/K.

  • 123.
    Thormann, Esben
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Yun, Sang Ho
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Amontonian Friction Induced by Flexible Surface Features on Microstructured Silicon2011In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 3, no 9, p. 3432-3439Article in journal (Refereed)
    Abstract [en]

    Friction between nonadhering sliding surfaces are normally described by Amontons' law, which states that there exists a linear relationship between the friction force and the normal applied load and that the friction force is independent of the macroscopic contact area between the surfaces and the sliding velocity. In this study we have measured friction as a function of applied load between a spherical silica particle and a microstructured silicon surface consisting of arrays of vertical microneedles, and we have challenged Amontons' law by changing the size of the silica particle and the sliding velocity. First, when looking at the friction as a function of time for a given applied load, the friction force was observed to oscillate with a period related to the spacing between the microneedles when using a small silica particle, whereas the friction force exhibited a more random variation when a larger silica particle was used. The oscillation in the friction force is a direct evidence for bending and release of individual microneedles and the observation illustrates that the energy dissipating mechanism becomes hidden in the friction data when the dimensions of the sliding body becomes much larger than the length scale of the surface features causing the friction. Second, when looking at the average friction force as a function of applied load we find, in accordance with Amontons' law, a linear relationship between the friction force and the applied load and the friction force is independent of both the size of the sliding silica particle and of the sliding velocity. One exception from this, however, was observed when sliding a small silica particle at low velocity, where a deviation from Amontons' law was noticed. The deviation from Amontons' law is suggested to be attributed to a change in the energy dissipating mechanism giving rise to the friction force. In light of that it is suggested that Amontons' law only is valid as long as the main energy dissipating mechanism does not change with the applied load. To get a better understanding of the general validity of Amontons' law, our results were evaluated against different microscopic models.

  • 124.
    Tian, Jie
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Ma, Zhe
    Li, Qiang
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Song, Yi
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Quantum Electronics and Quantum Optics, QEO.
    Liu, Zhihong
    Yang, Qing
    Zha, Chaolin
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Tong, Limin
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Nanowaveguides and couplers based on hybrid plasmonic modes2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 97, no 23, p. 231121-Article in journal (Refereed)
    Abstract [en]

    Experimental demonstration of silicon nanowires based hybrid plasmonic waveguides and couplers with subwavelength mode confinement at the near infrared wavelength lambda = 980 nm are presented. By measuring the radiating light from the discontinuities in a nanowire, the estimated propagation length of the hybrid plasmonic waveguide is about 30 mu m (corresponding to a propagation loss of similar to 0.14 dB/mu m). For the coupler, the experimental results show that the hybrid plasmonic modes can be efficiently coupled between two overlapping nanowires only with a 1.9 mu m long coupling length.

  • 125. Timopheev, A. A.
    et al.
    Ryabchenko, S. M.
    Kalita, V. M.
    Lozenko, A. F.
    Trotsenko, P. A.
    Stephanovich, V. A.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Munakata, M.
    The influence of intergranular interaction on the magnetization of the ensemble of oriented Stoner-Wohlfarth nanoparticles2009In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 105, no 8Article in journal (Refereed)
    Abstract [en]

    The influence of interparticle interaction on the processes of magnetization reversal is considered for an ensemble of oriented Stoner-Wohlfarth nanoparticles. This is done through a solution of a kinetic equation describing the relaxation of the total magnetization to its equilibrium value in an effective mean field which includes a term proportional to the instantaneous value of the magnetization. It is shown that the interparticle interaction influences the temperature dependence of a coercive field. Under certain conditions, the presence of the interparticle interaction can lead to the formation of the so-called superferromagnetic state with the correlated directions of the magnetic moments of the particles. If the system is unable to come to the equilibrium during the time interval necessary to perform measurements, some measured quantities become dependent on the measurement time. It is shown that the blocking temperature T-b and the temperature dependence of coercive field at T < T-b are strongly dependent on a measurement time. At T>T-b, however, the coercivity, if exists, does not depend on the measurement time. The data of magnetostatic measurements, carried out on the (CoFeB)(x)-(SiO2)(1-x) nanogranular films with the concentration of ferromagnetic particles slightly lower than a percolation threshold, are in compliance with the results of the calculations.

  • 126.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    Apparat och metod för generering av kortvågig elektromagnetisk strålning2008Patent (Other (popular science, discussion, etc.))
  • 127. Valenta, Jan
    et al.
    Bruhn, Benjamin
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    Coexistence of 1D and Quasi-0D Photoluminescence from Single Silicon Nanowires2011In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 11, no 7, p. 3003-3009Article in journal (Refereed)
    Abstract [en]

    Single silicon nanowires (Si-NWs) prepared by electron-beam lithography and reactive-ion etching are investigated by imaging optical spectroscopy under variable temperatures and laser pumping intensities. Spectral images of individual Si-NWs reveal a large variability of photoluminescence (PL) along a single Si-NW. The weaker broad emission band asymmetrically extended to the high-energy side is interpreted to be due to recombination of quasi-free 1D excitons while the brighter localized emission features (with significantly variable peak position, width, and shape) are due to localization of electron hole pairs in surface protrusions acting like quasi-0D centers or quantum dots (QDs). Correlated PL and scanning electron microscopy images indicate that the efficiently emitting QDs are located at the Si-NW interface with completely oxidized neck of the initial Si wall. Theoretical fitting of the delocalized PL emission band explains its broad asymmetrical band to be due to the Gaussian size distribution of the Si-NW diameter and reveals also the presence of recombination from the Si-NW excited state which can facilitate a fast capture of excitons into QD centers.

  • 128. Valenta, Jan
    et al.
    Bruhn, Benjamin
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Polarization of photoluminescence excitation and emission spectra of silicon nanorods within single Si/SiO2 nanowires2011In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 8, no 3, p. 1017-1020Article in journal (Refereed)
    Abstract [en]

    Polarization properties of individual silicon nanowires are studied using an optical micro-spectroscopy setup equipped with a Fresnel rhomb to rotate the polarization of the exciting laser and the analyzer to characterize the polarization of emitted photoluminescence. The Si nanowire samples are prepared by electron-beam lithography, plasma etching and oxidation. The fabricated wires are embedded in SiO2 and oriented parallel to the Si substrate. Due to the fluctuating wire diameter (around 5 nm) the very long wires (several tens of μm) are effectively divided into an array of quantum rods (prolate ellipsoids). These structures have strong photoluminescence under UV-blue excitation at room temperature. The degree of photoluminescence linear polarization of both excitation and emission is very high, between 0.9-1, and reveals relatively low fluctuations at different spots of the wires. Experimental results are compared with available theoretical models leading to the conclusion that the high polarization degree is mostly due to surface charges (dielectric confinement) with smaller contribution of quantum confinement effects.

  • 129. Valldor, M.
    et al.
    Esmaeilzadeh, S.
    Andersson, Magnus
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Morawski, A.
    Preparation and characterisation of the double perovskite Sr2TaMnO62006In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 299, no 1, p. 161-169Article in journal (Refereed)
    Abstract [en]

    The presented compound, Sr2TaMnO6, has a weak, disordered magnetic structure. The metal oxide was prepared under high isostatic oxygen pressure. The doubling of the perovskite structure was proven with electron diffraction and powder neutron diffraction. Combining neutron- and X-ray diffraction data, the room-temperature structure was modelled with the Rietveld method. Both octahedral positions are partially occupied by Mn and Ta, but with different Mn/Ta ratios. AC- and DC-magnetic measurements indicate a magnetic transition at about 17 K and the AC-magnetic susceptibility, both real and imaginary part, is frequency dependent, suggesting that the material has a spin-glass feature. The magnetic spins freeze during a wide temperature range and a possible explanation is a competative situation between the double exchange (ferromagnetism) and the super-exchange (anti-ferromagnetism).

  • 130. Vanin, E. V.
    et al.
    Grishin, Alexander M.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Khartsev, Sergiy
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    Tarasenko, O.
    Johansson, Petter
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Broadband photoluminescence from pulsed laser deposited Er2O3 films2006In: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 121, no 2, p. 256-258Article in journal (Refereed)
    Abstract [en]

    Photoluminescence (PL) with the bandwidth of 45 nm (1523-1568 nm, at the level of 3 dB) was observed in amorphous Er2O3 films grown on to the quartz substrate by pulsed laser ablation of erbium oxide stoichiometric target. Optical transmission spectrum has been fitted to Swanepoel formula to determine the dispersion of refractive index and to extract resonance absorption peaks at 980 and 1535 nm. The maximum gain coefficient of 800 dB/cm at 1535 nm was estimated using McCumber theory and experimental spectrum of the resonance absorption. In 5.7mm-long waveguide amplifier a theory predicts the spectral gain of 20dB with 1.4dB peak-to-peak flatness in the bandwidth of 31 nm (1532-1563 nm) when 73% of Er3+ ions are excited from the ground state to the I-4(13/2) laser level. Strong broadband PL at room temperature and inherently flat spectral gain promise Er2O3 films for ultra-short high-gain optical waveguide amplifiers and integrated light circuits.

  • 131.
    Wang, Ke
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101), Optics (Closed 20120101). Beijing Institute of Technology, China .
    Li, J.
    Djupsjöbacka, A.
    Chaciński, Marek
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    Westergren, Urban
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101), Photonics (Closed 20120101).
    Popov, Sergei Yu
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101), Optics (Closed 20120101).
    Jacobsen, G.
    Hurm, V.
    Makon, R. E.
    Driad, R.
    Walcher, H.
    Rosenzweig, J.
    Steffan, A. G.
    Giorgis Mekonnen, G.
    Bach, H. -G
    Li, Z.
    Friberg, Ari
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101), Optics (Closed 20120101).
    100-112 Gbit/s complete ETDM systems based on monolithically integrated transmitter and receiver modules2011In: Journal of Beijing Institute of Technology (English Edition), ISSN 1004-0579, Vol. 20, no 3, p. 410-414Article in journal (Refereed)
    Abstract [en]

    Traditional intensity modulated two-level electrical time-division multiplexing (ETDM) transmission systems working at 100-112 Gbit/s were investigated. The complete ETDM systems based on monolithically integrated transmitter and receiver modules were demonstrated with bit-error-rate (BER) performance of 10-8 at 107 Gbit/s, and near error-free standard forward error correction (FEC) threshold (2×10-3) at 112 Gbit/s. The experiment results showed that directly modulated high-speed ETDM transmission systems with the symbol rates at 100 Gbaud and beyond were promising candidate for cost-effective 100 GbE applications and might be a preform of the next generation of Terabit/s Ethernet.

  • 132.
    Wojek, Bastian M.
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    Buczko, R.
    Safaei, S.
    Dziawa, P.
    Kowalski, B. J.
    Hårdensson Berntsen, Magnus
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    Balasubramanian, T.
    Leandersson, M.
    Szczerbakow, A.
    Kacman, P.
    Story, T.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    Spin-polarized (001) surface states of the topological crystalline insulator Pb0.73Sn0.27Se2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 11, p. 115106-Article in journal (Refereed)
    Abstract [en]

    We study the nature of (001) surface states in Pb0.73Sn0.27Se in the newly discovered topological-crystalline-insulator (TCI) phase as well as the corresponding topologically trivial state above the band-gap-inversion temperature. Our calculations predict not only metallic surface states with a nontrivial chiral spin structure for the TCI case, but also nonmetallic (gapped) surface states with nonzero spin polarization when the system is a normal insulator. For both phases, angle- and spin-resolved photoelectron spectroscopy measurements provide conclusive evidence for the formation of these (001) surface states in Pb0.73Sn0.27Se, as well as for their chiral spin structure.

  • 133.
    Wojek, Bastian M.
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    Hårdensson Berntsen, Magnus
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    Boseggia, S.
    Boothroyd, A. T.
    Prabhakaran, D.
    McMorrow, D. F.
    Ronnow, H. M.
    Chang, J.
    Tjernberg, Oscar
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    The J(eff)=1/2 insulator Sr3Ir2O7 studied by means of angle-resolved photoemission spectroscopy2012In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 24, no 41, p. 415602-Article in journal (Refereed)
    Abstract [en]

    The low-energy electronic structure of the J(eff) = 1/2 spin-orbit insulator Sr3Ir2O7 has been studied by means of angle-resolved photoemission spectroscopy. A comparison of the results for bilayer Sr3Ir2O7 with available literature data for the related single-layer compound Sr2IrO4 reveals qualitative similarities and similar J(eff) = 1/2 bandwidths for the two materials, but also pronounced differences in the distribution of the spectral weight. In particular, photoemission from the J(eff) = 1/2 states appears to be suppressed. Yet, it is found that the Sr3Ir2O7 data are in overall better agreement with band-structure calculations than the data for Sr2IrO4.

  • 134.
    Wosinski, Lech
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Zhu, Ning
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Jaskorzynska, Bozena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Silicon-Based Integrated Multiplexers for WDM Systems2009In: ICTON: 2009 11TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS, NEW YORK: IEEE , 2009, p. 1267-1270Conference paper (Refereed)
    Abstract [en]

    Wavelength Division Multiplexing systems use multiplexers and demultiplexers to increase network capacity by allowing several information channels to be placed into one fiber. Depending on the application multiplexers and demultiplexers can have wide, coarse or dense channel spacing as well as different number of channels that they process. There are many techniques available today for realization of these passive, wavelength selective components including: thin film filters, Bragg gratings, arrayed waveguide gratings and echelle gratings. The last two solutions appear to be most suitable for wafer scale mass production. Silicon-based technology additionally allows for a high level of integration and compatibility with CMOS processing. Here we discuss issues related to different solutions and fabrication technologies and compare two of them based on planar lightwave circuits. We will illustrate with designed and fabricated components for different applications.

  • 135. Xiao, Dun
    et al.
    Liu, Yaowen
    Zhou, Y.
    Mohseni, Seyed Majid
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101). University of Gothenburg, Sweden; Shahid Beheshti University, Tehran, Iran.
    Chung, Sunjae
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. University of Gothenburg, Sweden.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. University of Gothenburg, Sweden.
    Merging droplets in double nanocontact spin torque oscillators2016In: Physical Review B, ISSN 2469-9950, Vol. 93, no 9, article id 094431Article in journal (Refereed)
    Abstract [en]

    We demonstrate how magnetic droplet soliton pairs, nucleated by two separated nanocontact (NC) spin torque oscillators, can merge into a single droplet soliton. A detailed description of the magnetization dynamics of this merger process is obtained by micromagnetic simulations: A droplet pair with a steady-state in-phase spin precession is generated through the spin-transfer torque effect underneath two separate NCs, followed by a gradual expansion of the droplets' volume and the out-phase of magnetization on the inner side of the two droplets, resulting in the droplets merging into a larger droplet. This merger occurs only when the NC separation is smaller than a critical value. A transient breathing mode is observed before the merged droplet stabilizes into a steady precession state. The precession frequency of the merged droplet is lower than that of the droplet pair, consistent with its larger size. Merged droplets can again break up into droplet pairs at high enough magnetic field with a strong hysteretic response.

  • 136.
    Yu, Shun
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    Molecular Interaction of Thin Film Photosensitive Organic Dyes on TiO2 Surfaces2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The photosensitive molecule adsorption on titanium dioxide (TiO2) forms the so-called “dye sensitized TiO2” system, a typical organic/oxide heterojunction, which is of great interest in catalysis and energy applications, e.g. dye-sensitized solar cell (DSSC). Traditionally, the transition metal complex dyes are the focus of the study. However, as the fast development of the organic semiconductors and invention of new pure organic dyes, it is necessary to expand the research horizon to cover these molecules and concrete the fundamental understanding of their basic properties, especially during sensitization.In this work, we focus on two different photosensitive molecules: phthalocyanines and triphenylamine-based dyes. Phthalocyanines are organic semiconductors with symmetric macro aromatic molecular structures. They possess good photoelectrical properties and good thermal and chemical stability, which make them widely used in the organic electronic industries. Triphenylamine-based dyes are new types of pure organic dyes which deliver high efficiency and reduce the cost of DSSC. They can be nominated as one of the strong candidates to substitute the ruthenium complex dyes in DSSC. The researches were carried out using classic surface science techniques on single crystal substrates and under ultrahigh vacuum condition. The photosensitive molecules were deposited by organic molecular beam deposition. The substrate reconstruction and ordering were checked by low energy electron diffraction. The molecular electronic, geometric structures and charge transfer properties were characterized by photoelectron spectroscopy, near edge X-ray absorption fine structure spectroscopy and resonant photoelectron spectroscopy (RPES). Scanning tunneling microscopy is used to directly image the molecular adsorption.For phthalocyanines, we select MgPc, ZnPc, FePc and TiOPc, which showed a general charge transfer from molecule to the substrate when adsorbed on rutile TiO2(110) surface with 1×1 and 1×2 reconstructions. This charge transfer can be prevented by modifying the TiO2 surface with pyridine derivatives (4-tert-butyl pyridine (4TBP), 2,2’-bipyridine and 4,4’-bipyridine), and furthermore the energy level alignment at the interface is modified by the surface dipole established by the pyridine molecules. Annealing also plays an important role to control the molecular structure and change the electronic structure together with the charge transfer properties, shown by TiOPc film. Special discussions were done for 4TBP for its ability to shift the substrate band bending by healing the oxygen vacancies, which makes it an important additive in the DSSC electrolyte. For the triphenylamine-based dye (TPAC), the systematic deposition enables the characterization of the coverage dependent changes of molecular electronic and geometric structures. The light polarization dependent charge transfer was revealed by RPES. Furthermore, the iodine doped TPAC on TiO2 were investigated to mimic the electrolyte/dye/TiO2 interface in the real DSSC.The whole work of this thesis aims to provide fundamental understanding of the interaction between photosensitive molecules on TiO2 surfaces at molecular level in the monolayer region, e.g. the formation of interfacial states and the coverage dependent atomic and electronic structures, etc. We explored the potential of the application of new dyes and modified of the existing system by identifying their advantage and disadvantage. The results may benefit the fields of dye syntheses, catalysis researches and designs of organic photovoltaic devices.

  • 137.
    Yu, Shun
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Ahmadi, Sareh
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Palmgren, Pal
    Hennies, Franz
    Zuleta, Marcelo
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Modification of Charge Transfer and Energy Level Alignment at Organic/TiO2 Interfaces2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 31, p. 13765-13771Article in journal (Refereed)
    Abstract [en]

    Adsorption of titanyl phthalocyanine (TiOPc) on rutile TiO2(110) modified by a set of pyridine derivatives (2,2'-bipyridine, 4,4'-bipyridine, and 4-tert-butyl pyridine) has been investigated using synchrotron radiation based X-ray photoelectron spectroscopy (XPS). For the unmodified TiOPc/TiO2 system, a strong charge transfer is observed from the first layer TiOPc into the substrate, which leads to a molecular layer at the interface with a depleted highest occupied molecular orbital (HOMO). However, precovering the TiO2 surface with a saturated pyridine monolayer effectively reduce this process and leave the TiOPc in a less perturbed molecular state. Furthermore, the TiOPc HOMO and core levels are observed at different binding energies ranging by 0.3 eV on the three pyridine monolayers, which is ascribed to differences in surface potentials set up by the different pyridine/TiO2 systems.

  • 138.
    Yu, Shun
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Ahmadi, Sareh
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Palmgren, Pål
    Lund University.
    Hennies, Franz
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Zuleta, Marcelo
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Adsorption of TiOPc on 1×1 and 1×2 reconstructed Rutile TiO2(110) SurfacesManuscript (preprint) (Other academic)
    Abstract [en]

    Ultrathin titanyl phthalocyanine (TiOPc) layers have been studied on rutile TiO2 (110) 1×1 and 1×2 surfaces by synchrotron radiation based photoelectron spectroscopy (PES) and scanning tunneling microscopy (STM). The adsorption mode of TiOPc on the surface is of great interest in that it is strongly related to the efficiency of the charge transfer process between dye and surface. Core level spectra show that two different adsorption states coexist on both surfaces; an interfacial state that has strong interaction with the substrate while the other retains its molecular characteristics. The bonding for the interfacial state is suggested to be mainly in the 1×1 areas. Annealing significantly changes the distribution of molecules with a preferential adsorption along steps and (1x2) strands.

  • 139.
    Yu, Shun
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Ahmadi, Sareh
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Sun, Chenghua
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Palmgren, Pal
    Hennies, Franz
    Zuleta, Marcelo
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    4-tert-Butyl Pyridine Bond Site and Band Bending on TiO2(110)2010In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 5, p. 2315-2320Article in journal (Refereed)
    Abstract [en]

    In the present work, we study the bonding of 4-tert-butyl pyridine (4TBP) to the TiO2(110) surface using photoelectron spectroscopy (PES) and density functional theory (DFT) calculations. The results show that at low coverage, 4TBP adsorbs preferentially on oxygen vacancies. The calculated adsorption energy at the vacancies is 120 kJ/mol larger than that oil the five-fold-coordinated Ti4+ sites located in the rows on the TiO2 surface. The vacancy is "healed" by 4TBP, and the related gap state is strongly reduced through charge transfer into empty pi* orbitals on the pyridine ring. This leads to a change in surface band bending by 0.2 eV toward lower binding energies. The band bending does not change with further 4TBP deposition when saturating the surface to monolayer coverage, where the TiO2 surface is effectively protected against further adsorption by the dense 4TBP layer.

  • 140.
    Yu, Shun
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Ahmadi, Sareh
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Sun, Chenghua
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Schulte, Karina
    Pietzsch, Annette
    Hennies, Franz
    Zuleta, Marcelo
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Crystallization-Induced Charge-Transfer Change in TiOPc Thin Films Revealed by Resonant Photoemission Spectroscopy2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 30, p. 14969-14977Article in journal (Refereed)
    Abstract [en]

    Organic semiconductors usually demonstrate crystal structure dependent electronic properties, and through precise control of film structure, the performance of novel organic electronic devices can be greatly improved. Understanding the crystal structure dependent charge-transfer mechanism thus becomes critical. In this work, we have prepared amorphous titanyl phthalocyanine films by vacuum molecular beam evaporation and have further crystallized them through vacuum annealing. In the crystalline phase, an excited electron is rapidly transferred into neighboring molecules; while in the amorphous phase, it is mainly localized and recombines with the core hole as revealed by resonant photoemission spectroscopy (RPES). The fast electron transfer time is determined to be around 16 fs in the crystalline film, which is in good agreement with the charge-transfer hopping time estimated from the best device performance reported. The crystallized film shows more p-type characteristics than the amorphous with all the energy levels shifting toward the vacuum level. However, the greatly improved charge transfer is assigned to the molecular orbital coupling rather than this shift. From density functional theory and RPES, we specify the contribution of two differently coordinated nitrogen atoms (N2c and N3c) to the experimental results and illustrate that the N3c related orbital has experienced a dramatic change, which is keenly related to the improved charge transfer.

  • 141.
    Yu, Shun
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Ahmadi, Sareh
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Zuleta, Marcelo
    Tian, Haining
    Schulte, Karina
    Pietzsch, Annette
    Hennies, Franz
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Yang, Xichuan
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Adsorption geometry, molecular interaction, and charge transfer of triphenylamine-based dye on rutile TiO2(110)2010In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 133, no 22, p. 224704-Article in journal (Refereed)
    Abstract [en]

    The fast development of new organic sensitizers leads to the need for a better understanding of the complexity and significance of their adsorption processes on TiO2 surfaces. We have investigated a prototype of the triphenylamine-cyanoacrylic acid (donor-acceptor) on rutile TiO2 (110) surface with special attention on the monolayer region. This molecule belongs to the type of dye, some of which so far has delivered the record efficiency of 10%-10.3% for pure organic sensitizers [W. Zeng, Y. Cao, Y. Bai, Y. Wang, Y. Shi, M. Zhang, F. Wang, C. Pan, and P. Wang, Chem. Mater. 22, 1915 (2010)]. The molecular configuration of this dye on the TiO2 surface was found to vary with coverage and adopt gradually an upright geometry, as determined from near edge x-ray absorption fine structure spectroscopy. Due to the molecular interaction within the increasingly dense packed layer, the molecular electronic structure changes systematically: all energy levels shift to higher binding energies, as shown by photoelectron spectroscopy. Furthermore, the investigation of charge delocalization within the molecule was carried out by means of resonant photoelectron spectroscopy. A fast delocalization (similar to 1.8 fs) occurs at the donor part while a competing process between delocalization and localization takes place at the acceptor part. This depicts the "push-pull" concept in donor-acceptor molecular system in time scale. (C) 2010 American Institute of Physics. [doi:10.1063/1.3509389]

  • 142.
    Yun, Sang Ho
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Dibos, A.
    Lee, Hyung-Seok
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wu, J. Z.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Growth of boron nano-junctions2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 15, p. 5587-5589Article in journal (Refereed)
    Abstract [en]

    In this work, we demonstrate the synthesis of various types of boron nanowire junctions in a self-assembled manner by simple closed-tube thermal vapor transfer method. The Y-type boron nano-junctions and lateral boron-silicon alloy nano-junctions were grown on Si substrates, based on the oxide assisted VLS growth mode at a relatively low processing temperature regime and the VLS growth mode at the high processing temperature regime, respectively.

  • 143.
    Zha, Chaolin
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Bonetti, Stefano
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Persson, Johan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Zhou, Yan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Pseudo-spin-valve with L1(0) (111)-oriented FePt fixed layer2009In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 105, no 7, p. 07E910-Article in journal (Refereed)
    Abstract [en]

    Recently we proposed a spin torque oscillator where the fixed layer has its magnetization easy-axis tilted with respect to the film plane to simultaneously achieve zero-field operation and high output power [Y. Zhou, C. L. Zha, S. Bonetti, J. Persson, and J. angstrom kerman, Appl. Phys. Lett. 92, 262508 (2008)]. Here we take the first step toward the realization of this device and fabricate successfully a pseudo-spin-valve using an L1(0) (111)-oriented FePt fixed layer with tilted magnetocrystalline anisotropy. A total magnetoresistance (MR) of 0.86% is experimentally observed for the standard pseudo-spin-valve of the L1(0) FePt/Cu/NiFe structure in applied fields up to 1.5 T. While part of the MR may originate from the FePt film alone, the dominating part of MR correlates with switching of the NiFe free layer.

  • 144.
    Zha, Chaolin
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Dumas, R. K.
    Lau, J. W.
    Mohseni, Seyed Majid
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Redjai Sani, Sohrab
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Golosovsky, I. V.
    Monsen, Á. F.
    Nogués, Josep
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Nanostructured MnGa films on Si/SiO(2) with 20.5 kOe room temperature coercivity2011In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 110, no 9, p. 093902-Article in journal (Refereed)
    Abstract [en]

    Nanostructured Mn(67)Ga(33) films exhibiting high room temperature coercivity (H(C) = 20.5 kOe) have been prepared by sputtering onto thermally oxidized Si substrates. Both the morphology and the coercivity of the films can be tuned by varying the growth parameters. The low deposition rate film, sputtered at a reduced power and working pressure, demonstrates a discontinuous island-like growth and the highest H(C). The large H(C) is linked to the presence of the high anisotropy DO(22) Mn(3)Ga phase and the single domain character of the exchange isolated, dipolar interacting, single crystal islands.

  • 145.
    Zha, Chaolin
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Pseudo spin valves based on L1(0) (111)-oriented FePt and FePtCu fixed layer with tilted anisotropy2010In: INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009) / [ed] Goll, G; Lohneysen, HV; Loidl, A; Pruschke, T; Richter, M; Schultz, L; Surgers, C; Wosnitza, J, BRISTOL: IOP PUBLISHING LTD , 2010, Vol. 200, p. UNSP 052036-Conference paper (Refereed)
    Abstract [en]

    We demonstrate a series of pseudo-spin-valve structures based on L1(0) (111)-oriented FePt and FePtCu with titled magnetocrystalline anisotropy. Highly ordered (111)-oriented L1(0) FePtCu with large anisotropy is achieved by optimizing the Cu content. Magnetoresistance (MR) up to 5% has been obtained by i) optimizing the fixed-layer growth using different underlayers, ii) enhancing the interface spin polarization using thin CoFe at the Cu interfaces, and iii) adjusting the Cu spacer thickness. The substantial MR realized with tilted fixed layer magnetization is an important prerequisite for the realization of tilted polarizer Spin Torque Oscillators (STO) or Spin-Transfer Torque Magnetoresistive Random Access Memories (STT-MRAM).

  • 146.
    Zhou, Yan
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Shin, Franklin G.
    Guan, Bo
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Capacitance Effect on Microwave Power Spectra of Spin-Torque Oscillator With Thermal Noise2009In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 45, no 6, p. 2773-2776Article in journal (Refereed)
    Abstract [en]

    A macro-spin simulation has been carried out to study the thermal stability of a spin-torque oscillator (STO) connected in parallel with a capacitance. To study the impact of realistic thermal fluctuation on an STO, a stochastic magnetic field vector is added into the Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation. From the numerical solution, it is found that the addition of capacitance positively influences the thermal stability of the system, and can improve the quality factor of the microwave power spectrum even in the presence of thermal fluctuation. The results of I-V phase shift under different conditions suggest that there may exist an optimum capacitance for which the thermal stability of the system can be most enhanced.

  • 147.
    Zhou, Yan
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Zha, Chaolin
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Bonetti, Stefano
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Persson, Johan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Microwave generation of tilted-polarizer spin torque oscillator2009In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 105, no 7, p. 07D116-Article in journal (Refereed)
    Abstract [en]

    Microwave frequency generation in a spin torque oscillator (STO) with a tilted fixed layer magnetization is studied using numerical simulation of the Landau-Lifshitz-Gilbert-Slonczewski equation. The dependence of the STO free layer precession frequency on drive current is determined as a function of fixed layer tilt angle. We find that zero-field STO operation is possible for almost all tilt angles, which allow for great freedom in choosing the detailed layer structure of the STO.

  • 148. Zhou, Yan
    et al.
    Zhang, Hong
    Liu, Yaowen
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Macrospin and micromagnetic studies of tilted polarizer spin-torque nano-oscillators2012In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 112, no 6, p. 063903-Article in journal (Refereed)
    Abstract [en]

    Using nonlinear dynamical systems theory, we analytically studied a spin-torque device in which the magnetization of the polarizer (the fixed layer) is tilted at an arbitrary angle out of the thin-film plane. While the analytical theory can determine the major features of the system, macrospin simulations were employed to demonstrate the unique characteristics of the system, such as the hysteretic switching between bistable states. Material dependencies of the dynamic and static state diagrams were also studied in the framework of the macrospin model. Full-scale micromagnetics simulations were finally performed to reveal more subtle features of the dynamics of such tilted polarizer systems. Both the macrospin and micromagnetics simulations gave quantitatively the same results as our analytical theory.

  • 149.
    Zuleta, Marcelo
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Edvinsson, Tomas
    Yu, Shun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Ahmadi, Sareh
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Boschloo, Gerrit
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Hagfeldt, Anders
    Light-induced rearrangements of chemisorbed dyes on anatase(101)2012In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 14, no 30, p. 10780-10788Article in journal (Refereed)
    Abstract [en]

    Photoinduced molecular rearrangements are important in daily events essential for life such as visual perception and photo-protection of light harvesting complexes in plants. In this study we demonstrate that similar photoarrangements appear in an analogous technological application where the device performance is controlled by chromophores in sensitized anatase TiO2, one of the main components for light-harvesting in dye-sensitized solar cells (DSC). STM reveals that illumination leads to distortions of organic dyes containing conjugated backbones and of cis-bis(isothiocyanate)-bis-(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II)-bis(tetrabutylammonium), known as N719. The dyes were adsorbed in a closed-packed mode on an anatase(101) single crystal surface and imaged in the dark and under white light illumination in an ultra-high vacuum (UHV). STM images of N719 clearly suggest rearrangements caused by rotation of the dye. Conversely, organic dyes rearrange by photoisomerization depending on the number of double bonds, their position in the molecular structure and on the ligand modifications.

  • 150.
    Önsten, Anneli
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Surface Reactivity and Electronic Structure of Metal Oxides2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

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