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PHOIBOS 150 MCD

Hemipsherical Energy Analyzer with MCD Detector for UPS, XPS, ISS and LEISS. 

The PHOIBOS 150 Hemispherical Energy Analyzer is a powerful tool for modern photoelectron spectroscopy. This analyzer can be operated in all relevant analysis modes, such as XPS, UPS, as well as AES, ISS and LEISS. Its design and the modular supplementary hardware makes this analyzer the most versatile PES analyzer in the market. It can easily be upgraded with all available SPECS detection systems. 

The integrated MCD-9 (9 channel multi channeltron detector) detector is a well established and robust detection solution. The direct detection of electron signals yield quantitative counts per second (cps). With 9 simultaneous channels aquisition with high count rates can be guaranteed.

The energy analyzer section is equipped with 8 customizable entrance and 3 exit slits for UPS and XPS. The analyzer comes with a highly stable power supply, the HSA 3500 plus, for best performance in a wide kinetic energy range up to 3500 eV.

KEY FEATURES

  • Robust and Performant Analyzer for XPS, UPS, AES, ISS and LEIS
  • 150 mm Mean Radius
  • Quantitative Analysis
  • High Count Rate and Linearity
  • 9 Simultaneous Energy Channels
  • Robust Detector Technology
  • Double µ-Metal Shielding

MADE FOR THESE METHODS

1

SPECIFICATIONS

PHOIBOS 150 MCD
Operation
Energy Dispersion by

Hemisphere

Slits/Apertures

8 Entrance, 3 Exit slits and Iris aperture

Lens Modes

  • Angular resolved Mode
  • Transmission Mode
  • Spatially resolved Mode
  • Acceptance Angle

    ±15°

    Kinetic Energy Range

    0 - 3500 eV

    Pass Energies

    0 - 550 eV continously adjustable

    Detector

    MCD 9

    Detector Channels

    9

    Measurement Modes

  • Sweeping Mode
  • Fixed Mode
  • Energy Window

    23% of Pass Energy

    Electronics

    HSA 3500 plus HT 100

    Working Pressure

    10-11 to 10-7 mbar

    Mounting
    Mounting Flange

    DN100 CF

    Magnetic Shielding

    Double µ-Metal Shielding

    Working Distance

    40 mm

    Electric Isolation

    up to 7 keV

    Performance
    Angular Resolution

    < 0.5°

    Energy Resolution

    <10 meV for XPS

    Lateral Resolution

    < 100 µm

    XPS Count Rates UHV

    Ag 3d measured with XR 50 300 W MgKa > 3 Mcps @ 0.85 eV, > 9 Mcps @ 1.00 eV

    APPLICATION NOTES

    PUBLICATIONS

    1. (2016) Bottom-Up Synthesis of Metalated Carbyne

      Because of stability issues, carbyne, a one-dimensional chain of carbon atoms, has been much less investigated than other recent carbon allotropes such as graphene. Beyond that, metalation of such a linear carbon nanostructure with regularly distributed metal atoms is even more challenging. Here we report a successful on-surface synthesis of metalated carbyne chains by dehydrogenative coupling of ethyne molecules and copper atoms on a Cu(110) surface under ultrahigh-vacuum conditions. The length of the fabricated metalated carbyne chains was found to extend to the submicron scale (with the longest ones up to ∼120 nm). We expect that the herein-developed on-surface synthesis strategy for the efficient synthesis of organometallic carbon-based nanostructures will inspire more extensive experimental investigations of their physicochemical properties and explorations of their potential with respect to technological applications.



      Q. Sun, L. Cai, S. Wang, R. Widmer, H. Ju, J. Zhu, L. Li∥, Y. He, P. Ruffieux, R. Fasel, W. Xu
      J. Am. Chem. Soc. 138 (4), pp. 1106–1109
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    2. (2014) Direct observation of spin-resolved full and empty electron states in ferromagnetic surfaces

      We present a versatile apparatus for the study of ferromagnetic surfaces, which combines spin-polarized photoemission and inverse photoemission spectroscopies. Samples can be grown by molecular beam epitaxy and analyzed in situ. Spin-resolved photoemission spectroscopy analysis is done with a hemispherical electron analyzer coupled to a 25 kV-Mott detector. Inverse photoemission spectroscopy experiments are performed with GaAs crystals as spin-polarized electron sources and a UV bandpass photon detector. As an example, measurements on the oxygen passivated Fe(100)-p(1×1)O surface are presented.



      G. Berti, A. Calloni, A. Brambilla, G. Bussetti, L. Duò, F. Ciccacci
      Review of Scientific Instruments 85, 073901
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    3. (2012) Preparation and investigation of the A-site and B-site terminated SrTiO3(001) surface: A combined experimental and theoretical x-ray photoelectron diffraction study

      We have investigated surface composition, structure, and termination of SrTiO3(001) samples (STO) following typical steps of standard ex situ and in situ preparation procedures by performing x-ray photoelectron spectroscopy (XPS) and x-ray photoelectron diffraction (XPD) experiments, and multiple scattering cluster (MSC) calculations. XPS has confirmed the presence of Sr2+, Ti4+, and O2−related to STO. Well-developed diffraction features have been observed in all XPD polar scans demonstrating the good structural ordering of the investigated surfaces. In order to permit a detailed comparison of XPD experiment and theory, we have especially taken care of effects due to the angular dependent instrument function by applying a new ratio procedure. Thus, we achieved a very good agreement between results of MSC calculations and experimental angular distributions. A fingerprint region has been identified in Sr3d polar scans, which has exhibited both evident dependencies on surface preparation steps in the experiments and clear sensitivity to surface termination in the theoretical modeling. In this manner, we have been able to describe as-received samples and in situ-treated samples as being TiO2- and SrO-terminated, respectively. Standard buffered hydrofluoric acid-treated samples turned out to be mostly TiO2-terminated but with a non-negligible admixture of different, likely SrO-type termination.



      C. Raisch, T. Chassé, Ch. Langheinrich, A. Chassé
      Journal of Applied Physics 112, 073505
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    4. (2011) An instrument for the investigation of actinides with spin resolved photoelectron spectroscopy and bremsstrahlung isochromat spectroscopy

      A new system for spin resolved photoelectron spectroscopy and bremsstrahlung isochromat spectroscopy has been built and commissioned at Lawrence Livermore National Laboratory for the investigation of the electronic structure of the actinides. Actinide materials are very toxic and radioactive and therefore cannot be brought to most general user facilities for spectroscopic studies. The technical details of the new system and preliminary data obtained therein will be presented and discussed.



      S.-W. Yu, J. G. Tobin, B. W. Chung
      Review of Scientific Instruments 82, 093903
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    5. (2010) Electronic structure of LiCoO2 thin films: A combined photoemission spectroscopy and density functional theory study

      The electronic properties of LiCoO2 have been studied by theoretical band-structure calculations (using density functional theory) and experimental methods (photoemission). Synchrotron-induced photoelectron spectroscopy, resonant photoemission spectroscopy (ResPES), and soft x-ray absorption (XAS) have been applied to investigate the electronic structure of both occupied and unoccupied states. High-quality PES spectra were obtained from stoichiometric and highly crystalline LiCoO2 thin films deposited “in situ” by rf magnetron sputtering. An experimental approach of separating oxygen- and cobalt-derived (final) states by ResPES in the valence-band region is presented. The procedure takes advantage of an antiresonant behavior of cobalt-derived states at the 3p−3d excitation threshold. Information about the unoccupied density of states has been obtained by O K XAS. The structure of the Co L absorption edge is compared to semiempirical charge-transfer multiplet calculations. The experimental results are furthermore compared with band-structure calculations considering three different exchange potentials [generalized gradient approximation (GGA), using a nonlocal Hubbard U (GGA+U) and using a hybrid functional (Becke, three-parameter, Lee-Yang-Parr [B3LYP])]. For these different approaches total density of states and partial valence-band density of states have been investigated. The best qualitative agreement with experimental results has been obtained by using a GGA+U functional with U=2.9 eV.



      D. Ensling, A. Thissen, S. Laubach, P.C. Schmidt, W. Jaegermann
      Phys. Rev. B 82, 195431
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    6. (2010) Application of nanostructured Ca doped CeO2 for ultraviolet filtration

      Calcium doped CeO2 nanoparticles with doping concentrations between 0 and 50 mol% were synthesized by a co-precipitation method for ultraviolet filtration application. Below 20 mol% doping concentration, the samples were single-phase. From 30 mol%, CaCO3 appears as a secondary phase. The calculated CeO2 mean crystallite size was 9.3 nm for the pure and 5.7 nm for the 50 mol% Ca-doped sample. Between 250 and 330 nm, the absorbance increased for the 10, 30, and 40 mol% Ca-doped samples compared to the pure one. The band-gap was found to be 3.20 eV for the undoped, and between 3.36 and 3.51 eV for the doped samples. The blue shifts are attributed to the quantum confinement effect. X-ray photoelectron spectroscopy showed that the Ce3+ atomic concentration in the pure sample was higher than that of the 20 mol% Ca-doped sample.



      L. Truffoult, M.-T. Ta, T. Devers, K. Konstantinov, V. Harel, C. Simmonard, C. Andreazza, I. P. Nevirkovets, A. Pineau, O. Veron, J. P. Blondeau
      Material Research Bulletin 45, pp. 527-535
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    7. (2009) X-ray photoelectron spectra of platinum compounds excited with monochromatic AgLα irradiation

      Non-monochromatic MgKα and monochromatic AgLα irradiations were used to measure Pt4f and Pt3d5/2 X-ray photoelectron spectra from platinum black and from several platinum compounds with different Pt oxidation states. The Pt3d5/2 core level binding energies from platinum compounds were measured for the first time. Potential of these data to XPS study of Pt/Al2O3 catalysts is demonstrated.



      A. V. Kalinkin, M. Yu. Smirnov, A. I. Nizovskii, V. I. Bukhtiyarov.
      Journal of Electron Spectroscopy and Related Phenomena 177, pp. 15-18
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    8. (2009) M5O14-like V-Mo-Nb oxide catalysts: Structure and catalytic performance

      Within Mo5O14-like structural type for mixed V–Mo–Nb oxides, the effect of vanadium and niobium content and treatment temperature on the phase composition, structure and catalytic properties of the samples in oxidative dehydrogenation of ethane has been studied. The limits of V and Nb content in the ternary Mo5O14-like oxide are determined. V–Mo–Nb oxides are shown to be the substitution solid solutions of composition (Mo0.6VzNb0.4−z)5O14 (0 < z < 0.2) based on binary oxide (Mo0.6Nb0.4)5O14. The structure of crystalline V–Mo–Nb oxides is refined. Crystallization of Mo5O14-like structure occurs at temperatures ≥550 °C. Below 550 °C, V–Mo–Nb oxides are nanocrystalline materials having a disordered layered structure with the interlayer distance of ca. 4 Å. The structural model of nanocrystalline oxides is discussed. The role of Nb in the formation of ternary V–Mo–Nb oxide compounds is revealed, and the surface state of these oxides at different temperatures is analyzed. The low-temperature V–Mo–Nb oxides are the most active catalysts in the reaction of ethane oxidative dehydrogenation. They are characterized by the ratio V/Nb ≈ 1 in the Mo5O14-like structure.



      T. Yu. Kardash, L. M. Plyasova, V. M. Bondareva, T. V. Andrushkevich, L. S. Dovlitova, A. I. Ischenko, A. I. Nizovskii, A. V. Kalinkin
      Applied Catalysis A: General 375 (1) , pp. 26-36
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    9. (2008) Breakdown of spatial inversion symmetry in core-level photoemission of Pt(001)

      We have measured the spin polarization of the 4d and 4f core-level photoelectrons from Pt(001) by using unpolarized laboratory x-ray sources under a highly bulk sensitive condition. The 4d and 4f photoelectrons are highly spin polarized perpendicular to the reaction plane as defined by the incident photons and the outgoing electrons. The measured spin polarization and a close look at the core-level photoemission process demonstrate that the bulk core-level photoemission with unpolarized light contributes to the measured spin polarization. This result is in contrast to the valence band photoemission from nonmagnetic solids, wherein the bulk cannot contribute to the measured spin polarization due to the existence of spatial inversion symmetry. Thus, the argument based on spatial inversion symmetry does not apply to the core-level photoemission. The measured spin polarization is in good agreement with an atomic model.



      S.-W. Yu, J. G. Tobin
      Phys. Rev. B 77, 193409
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    10. (2008) Origin of Carrier Types in Intrinsic Organic Semiconductors

      The factors determining carrier type in intrinsic organic semiconductors are clarified by measuring field‐effect transistor (FET) characteristics and electronic states for an identical specimen, which is transferred between the film growth/FET measurement and electron spectroscopy chambers in situ (see figure). The FET mobility is found to decrease exponentially with the precisely evaluated charge injection barrier both for electrons and holes.



      T. Kaji, S Enatni, S. Ikeda, K. Saiki
      Adv. Mater. 20 (11), pp. 2084-2089
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    11. (2007) Synthesis, Structure, and Reactivity of Cerium(IV) Calix[4]arene Complexes

      The equimolar reaction of Ce(hfac)4 (1) (hfac = 1,1,1,5,5,5‐hexafluoropentanedionato) with p‐tBu‐calix[4](OMe)2(OH)2 in toluene gave the new cerium(IV) calix[4]arene complex {p‐tBu‐calix[4](OMe)2(O)2}Ce(hfac)2 (2). The single‐crystal X‐ray structure shows the cone geometry of the calixarene ligand with the methoxy groups coordinated to the cerium; it shows slightly longer cerium–oxygen (acetylacetonate ligand) bond lengths than the corresponding bonds in the analogous nonfluorinated complex {p‐tBu‐calix[4](OMe)2(O)2}Ce(acac)2 (3). The bromination reaction of 3 gave the bisbrominated complex {p‐tBu‐calix[4](OMe)2(O)2}Ce(Br‐acac)2 (4). 1H NMR spectroscopic studies and a single‐crystal X‐ray structure of 4 revealed that the bromination took place in the 3‐position of the acac ligand. Furthermore, the first X‐ray photoelectron spectroscopy (XPS) evaluation of the Ce oxidation state in cerium calix[4]arene complexes 2 and 3 is presented, and X‐ray induced changes of Ceox in these complexes are detected. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)



      J. Gottfriedsen, R. Hagner, M. Spoida, Y. Suchorski
      Eur. J. Inorg. Chem. 2007 (16) pp. 2288–2295
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    12. (2007) Active species on γ-alumina-supported vanadia catalysts: Nature and reducibility

      The oxidation states and reducibility of γ-alumina-supported vanadium oxide catalysts with V loadings between 1.7 and 15.7 wt% were studied by means of temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) for fresh as well as used catalysts. As additional experimental techniques, X-ray diffraction (XRD), diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS), and temperature-programmed desorption (TPD) were applied. For V loadings up to 6.1 wt%, the surface was found to be covered only by vanadate, while at higher loadings the formation of V2O5 crystallites was observed. The XPS and TPR data showed that under moderate oxidizing conditions, only of V in the vanadate catalysts was in the oxidation state +5, while in the catalysts containing V2O5 crystallites it was about 80%, with the remainder being present as V(IV) in both cases. In the ambient pressure TPR experiments, all catalysts were completely reduced by hydrogen to V(III), although the vanadate catalysts were found to be more easily reducible than those containing V2O5. The V dispersion changed during redox cycles, as they appeared under working conditions. These changes were different for the exposure to ethane or hydrogen, but did not influence the maximum oxidation states. In the catalytic oxidation of ethane used as a model reaction, all catalysts were found to be in their oxidized state under steady-state conditions. Significant catalyst reduction occurred only if the surrounding gas-phase oxygen was completely consumed, leading to the loss of catalytic activity due to the disappearance of V(V) species. A novel structure for γ-alumina-supported vanadia catalysts is proposed on the basis of the experimental data.



      F. Klose, T. Wolff, H. Lorenz, A. Seidel-Morgenstern, Y. Suchorski, M. Piorkovska, H. Weiss
      J. of catalysis 247; pp. 176-193
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    13. (2007) Theoretical and experimental determination of the electronic structure of V2O5 reduced V2O5-x and sodium intercalated NaV2O5

      In this work the electronic structure of V2O5, reduced V2O5−x (V16O39) and sodium intercalated NaV2O5 has been studied by both theoretical and experimental methods. Theoretical band structure calculations have been performed using density functional methods (DFT). We have investigated the electron density distribution of the valence states, the total density of states (total DOS) and the partial valence band density of states (PVBDOS). Experimentally, amorphous V2O5 thin films have been prepared by physical vapour deposition (PVD) on freshly cleaved highly oriented pyrolytic graphite (HOPG) substrates at room temperature with an initial oxygen understoichiometry of about 4%, resulting in a net stoichiometry of V2O4.8. These films have been intercalated by sodium using vacuum deposition with subsequent spontaneous intercalation (NaV2O5) at room temperature. Resonant V3p–V3d photoelectron spectroscopy (ResPES) experiments have been performed to determine the PVBDOS focusing on the calculation of occupation numbers and the determination of effective oxidation state, reflecting ionicity and covalency of the V–O bonds. Using X-ray absorption near edge spectra (XANES) an attempt is made to visualize the changes in the unoccupied DOS due to sodium intercalation. For comparison measurements on nearly stoichiometric V2O5 single crystals have been performed. The experimental data for the freshly cleaved and only marginally reduced V2O5 single crystals and the NaV2O5 results are in good agreement with the calculated values. The ResPES results for V2O4.8 agree in principle with the calculations, but the trends in the change of the ionicity differ between experiment and theory. Experimentally we find partly occupied V 3d states above the oxygen 2p-like states and a band gap between these and the unoccupied states. In theory one finds this occupation scheme assuming oxygen vacancies in V2O5 and by performing a spin-polarized calculation of an antiferromagnetic ordered NaV2O5.



      S. Laubach, P. C. Schmidt, A. Thissen, F. J. Fernandez-Madrigal, Q. H. Wu, W. Jaegermann, M. Klemm, S. Horn
      Phys. Chem. Chem. Phys. 9, pp. 2564-2576
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    14. (2007) Variation of the Vanadium oxidation state within a VPO catalyst layer in a membrane reactor: XPS mapping and modelling

      Recently, the feasibility of butane oxidation in an electrochemical membrane reactor (EMR) using a vanadium phosphorus oxide (VPO) catalyst layer on a tubular anodic electrode has been reported. This novel application of EMR gives rise to questions about the vanadium oxidation state (Vox) under working conditions and about its spatial distribution in the catalyst layer. It has now been determined by means of position-resolved XPS measurements. In addition, model calculations on the spatial Vox distribution have been performed for the first time. The simulations reveal a non-uniform 3D distribution of Vox due to the relative rate of reduction and re-oxidation processes in the catalyst layer, in good agreement with the experimental XPS data.



      Y. Suchorski, B. Munder, S. Becker, L. Rihko-Struckmann, K. Sundmacher, H. Weiss
      Applied Surface Scinece 253, pp. 5904-5909
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    15. (2007) Observation of an underlyingrelativisticeffect in the valencebands of Pt

      We have measured the photoelectron spin polarization emitted by unpolarized UV radiation from the valence-bands of the well ordered Pt(0 0 1)-(5 × 1) surface and the disordered surface destroyed by Ar ions bombardment. Almost identical spin polarizations have been observed in both cases. This observation suggests that the electron spin polarization in photoemission caused by unpolarized light is determined by a short-range order of atoms. This finding has an obvious implication that the electron spin polarization in photoemission caused by unpolarized light can be used to study the bulk electronic structure of the nonmagnetic materials.



      S.-W. Yu, J. G. Tobin
      Surface Science 601, pp. L127–L131
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    16. (2007) Evaluation and X-Ra:y Induced Modification of the Cerium Oxidation State in Cerium Calixarene Complexes

      The cerium oxidation state in novel calixarene-supported cerium(IV) β-diketonate complexes [p-tBu-calix[4](OMe)2(O)2]Ce(acac)2 (1) and [p-tBu-calix[4](OMe)2(O)2]Ce(hfac)2 (2), which are a new class of potential precursors for homogeneous oxidative transformations, has been determined using X-ray photoelectron spectroscopy (XPS). Cerium oxidation states between 3.6 and 3.65 were detected, distinctly different from their nominal value of +4. An X-ray induced photoreduction of these compounds was detected. Because of the observed stability of the X-ray modified oxidation state under ambient conditions this effect might be used for a long-standing fine tuning of the Ce oxidation state in cerium calixarenes.



      Y. Suchorski, J. Gottfriedsen, R. Wrobel B. Strzelczyk, H. Weiss
      Solid State Phenomena 128; pp. 115-120
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    17. (2006) Bulk and surface properties of VPO catalyst used in an electrochemical membrane reactor: conductivity-, XRD-, TPO- and XPS-study

      In the first part of this work, the electrical conductivity of vanadium phosphorous oxide (VPO) catalyst was investigated by means of the 2-probe EIS method. The VPO showed an extremely low conductivity at low oxygen partial pressure, which is the prevailing condition in the anodic compartment in an electrochemical membrane reactor (EMR). In the second part of this study, fresh as well as VPO catalyst already used in an EMR were characterised with XRD, XPS and temperature programmed oxidation (TPO). The XRD measurements revealed an unchanged bulk phase structure after operation in the EMR. Significant differences in the average oxidation states of vanadium in the catalyst layer in the EMR were determined via XPS, where the catalyst surface facing the electrolyte membrane was more oxidised than the surface facing the anodic gas compartment. The lowered uptake and release of oxygen was observed in TPO experiments for the catalyst used in the EMR.



      L. K. Rihko-Struckmann, Y. Ye, L. Chalakov, Y. Suchorski, H. Weiss, K. Sundmacher
      Catalysis Letters 109, pp. 89-96
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    18. (2006) Poly(phenylene oxide) films modified with allylaminevplasma as a support for invertase immobilization

      The paper describes a method for preparation of polymer support suitable for covalent invertase immobilization. Modification of poly(phenylene oxide) films by plasma polymerization of allylamine has been applied to introduce amine functionality on the polymer surface. It has been observed that the polymer surface became covered in plasma by a loosely fixed, moderately hydrophilic layer that should be removed before the immobilization process. The chemical character of the stable sub-layer has been related to several modification parameters: geometry of reactor, mode of plasma action and composition of gaseous mixture. Methods for determination of surface concentration of amine groups have also been presented and discussed from the immobilization point of view.



      I. Gancarz, J. Bryjak, M. Bryjak, G. Poźniak, W. Tylus
      European Polymer Journal 42, pp. 2430-2440
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    19. (2005) Activation of binary Zr-V non-evaporable getters: synchrotron radiation photoemission study

      Zr–V alloy getter films were prepared on stainless steel substrates by magnetron sputtering. The thermal activation behavior of these getters was investigated by synchrotron radiation photoelectron spectroscopy using photon excitation energies of 600, 250 and 73 eV. Depth resolved results were compared to the results of the SIMS profiling. The measurements confirmed the disappearance of the superficial oxide layer covering the air-exposed Zr–V surfaces via its progressive reduction during the thermal activation. The depth sensitive results showed that the activated getter surface is covered by a residual zirconium sub-oxide.



      V. Matolín, V. Dudr, S. Fabík, V. Cháb, K. Mašek, I. Matolínová, K.C. Prince, T. Skála, F.Šutara, N. Tsud, K. Veltruská
      Applied Surface Science 243 (1-4), pp. 106-112
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    20. (2005) Surface structure of CuGaSe2 (001)

      Although chalcopyrites have been used as absorber in thin film solar cells for nearly 30 years, not much is known about their surface structure, which might be an important information towards growth and interface optimization. Surface reconstructions, a general feature of semiconductor surfaces, have not been reported on Cu-III–VI2 (001) surfaces so far. We have thus studied the chalcopyrite CuGaSe2 (001) surface preparation by Ar+ ion bombardment and annealing. The samples were grown by MOCVD on a (001) GaAs substrate on axis with a near-stoichiometric ratio Cu/Ga. The preparation was optimized so that we finally obtained a flat, well-ordered surface. The surface composition and structure was analyzed with AES, XPS, and LEED. On uncontaminated surfaces, a (1×4) reconstruction was observed with LEED which we tentatively interpret as a Se-terminated surface. XPS characterization shows a surface core level shift of −0.8 eV for the selenium surface atoms of the (1×4) reconstruction. Further investigations were carried out via AFM to characterize the surface morphology.



      Th. Deniozou, N. Esser, S. Siebentritt, P. Vogt, R. Hunger
      Thin Solid Films 480-481, pp. 382-387
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    21. (2005) Post deposition purification of PTCDA thin films

      The decomposition of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) molecules during evaporation of unpurified raw material in ultra high vacuum was studied. The fragments were identified by mass spectrometry and the influence of these fragments and further contaminations of the raw material on the electronic structure of PTCDA thin films was measured by photoemission spectroscopy. Annealing of contaminated PTCDA films was tested as cheap and easy to perform method for (partial) post deposition purification of the contaminated films.



      J. Wüsten, Th. Ertl, S. Lach, Ch. Ziegler
      Applied Surface Science 252, pp. 104-107
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    22. (2005) Elementary processes at semiconductor/electrolyte interfaces: perspectives and limits of electron spectroscopy

      Semiconductor device properties based on electrolyte contacts or modified by electrochemical reactions are dominated by the electronic structure of the interface. Electron spectroscopy as e.g. photoemission is the most appropriate surface science techniques to investigate elementary processes at semiconductor/electrolyte interfaces. For such investigations a specific experimental set-up (SoLiAS) has been built-up which allows performing model experiments as well as surface analysis after emersion under different experimental conditions. The experimental approach is presented by a number of experiments performed during the last years with GaAs as substrate material. Model experiments by adsorption and coadsorption of electrolyte species give information on fundamental aspects of semiconductor/electrolyte interactions. Emersion experiments give information on a final composition and the related electronic structure of electrodes after electrochemical reactions. The use of frozen electrolytes will help to bridge the gap between these two approaches. With the combination of the experimental procedures one may expect a detailed analysis of electrolyte (modified) interfaces covering chemical composition, electronic structure of surfaces/interfaces as well as surface/interface potentials.



      Th. Mayer, M. Lebedev, R. Hunger, W. Jaegermann
      Applied Surface Scinece 252, pp. 31-42
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    23. (2005) Spectroscopic characterization of alkaline earth uranyl carbonates

      A series of alkaline uranyl carbonates, M[UO2(CO3)3]·nH2O (M=Mg2, Ca2, Sr2, Ba2, Na2Ca, and CaMg) was synthesized and characterized by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS) after nitric acid digestion, X-ray powder diffraction (XRD), and thermal analysis (TGA/DTA). The molecular structure of these compounds was characterized by extended X-ray absorption fine-structure (EXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS). Crystalline Ba2[UO2(CO3)3]·6H2O was obtained for the first time. The EXAFS analysis showed that this compound consists of (UO2)(CO3)3 clusters similar to the other alkaline earth uranyl carbonates. The average U–Ba distance is 3.90±0.02 Å.Fluorescence wavelengths and life times were measured using time-resolved laser-induced fluorescence spectroscopy (TRLFS). The U–O bond distances determined by EXAFS, TRLFS, XPS, and Raman spectroscopy agree within the experimental uncertainties. The spectroscopic signatures observed could be useful for identifying uranyl carbonate species adsorbed on mineral surfaces.



      S. Amayri, T. Reich, T. Arnold, G. Geipel, G. Bernhard
      Journal of Solid State Chemistry 178 (2), pp. 567-577
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    24. (2005) Evolution of oxidation states in vanadium-based catalysts under conventional XPS conditions

      The stability of different vanadium-based catalysts for the selective oxidation of small hydrocarbons under the ultra-high vacuum (UHV) conditions of standard X-ray photoelectron spectroscopy (XPS) was studied by using a multi-purpose surface analysis apparatus which allows time spans of only a few minutes between the sample transfer into vacuum and the first photoelectron spectrum. For vanadium phosphorus oxide catalysts a significant dependence of the average vanadium oxidation state on the time of exposure to the UHV was observed, with a substantial decrease of the V+5/V+4 ratio within only a few minutes. A much less pronounced reduction was found for alumina-supported VOx catalysts. The observed changes are predominantly due to the vacuum environment with a rather minor (if at all) contribution of the X-ray excitation.



      Y. Suchorski, L. Rihko-Strckmann, F. Klose, Y. Ye, M. Alandjiyska, K. Sundmacher, H. Weiss,
      Applied Surface Science 249 (1-4), pp. 231-237
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    25. (2005) Electronic properties of the organic semiconductor hetero-interface CuPc/C60

      We present a study of the electronic properties of the interface between the well-established molecular organic semiconductor copper phthalocyanine (CuPc) and the fullerite C60 using photoelectron spectroscopy and the Kelvin-probe (KP) method. Upon deposition of CuPc on C60, we found interfacial shifts of the vacuum level indicating the formation of a dipole layer, while band bending is found to be negligible. The interface dipole of 0.5 eV measured with KP is close to the difference between the work functions of bulk CuPc and C60. No evidence for a chemical interaction at the interface is concluded from the absence of additional features in the core-level spectra at the earliest stages of deposition. The energy-level alignment diagram at the CuPc/C60 interface is derived.



      O. V. Molodtsova, T. Schwieger, M. Knupfer
      Applied Surface Science 252 (1), pp. 143-147
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    26. (2005) Synchrotron radiation photoemission study of indium oxide surface prepared by spray pyrolysis method

      In2O3 thin films with preferred (4 0 0) orientation prepared by the spray pyrolysis method were studied by synchrotron radiation photoemission and ion scattering spectroscopes. O 1s, O 2s, In 4d core level and valence band spectra were monitored at photon energies 660, 245, 150, and 73 eV to see their evolution with UHV treatments (heating, sputtering and exposure of oxygen). Reduction of the surface layer to nearly metallic indium was found with thermal treatment at T ≥ 300 °C. This surface demonstrates high reactivity to reversible oxidation/reduction processes. This was evidenced by evolution of the O 2s core level peak and of the band gap emission intensity. In spite of such surface reduction it was found that within a probing depth of ≤10 Å the material displays spectral features characteristic of stoichiometric In2O3. We tentatively explain such behavior in terms of the In2O3 crystallographic structure and some conclusions relating to gas-sensing properties were made.



      V. Brinzari, G. Korotcenkov, V. Matolin
      Applied Surface Science 243 (1-4), pp. 335-344
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    27. (2005) In Situ Studies of Methanol Decomposition an Oxidation on Pd(111) by PM-IRAS and XPS Spectroscopy

      Methanol decomposition and oxidation on Pd(111) at millibar pressure were studied by in situ polarization−modulation infrared reflection absorption spectroscopy (PM-IRAS), on-line gas chromatography and pre- and postreaction X-ray photoelectron spectroscopy (XPS). Various dehydrogenation products such as methoxy CH3O, formaldehyde CH2O, formyl CHO, and CO could be spectroscopically identified. Methanol oxidation proceeds via dehydrogenation to formaldehyde CH2O, which either desorbs or is further dehydrogenated to CO, which is subsequently oxidized to CO2. Carbonaceous overlayers that are present during the reaction may favorably affect the selectivity toward CH2O. The reaction takes place on metallic Pd, and no indications of an involvement of Pd surface oxide were observed.



      M. Borasio , O. Rodríguez de la Fuente, G. Rupprechter, H.-J. Freund
      J. Phys. Chem. B 109 (38), pp. 17791–17794
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    28. (2005) Photoelectron spectroscopy of nanocrystalline anatase TiO2 films

      Nanocrystalline TiO2 (anatase) films were prepared using either colloidal suspensions or a sol–gel route. The electronic structure of these films was analyzed using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). Apart from pristine films, films containing defects introduced by annealing under ultra-high vacuum conditions or by ion bombardment were investigated. Generally, annealing in the temperature range up to 720 K results in no significant changes in the XPS and UPS spectra as compared to the pristine state, indicating that the amount of defect formation is too low to be observable by these techniques. On the other hand, ion irradiation causes the appearance of distinct defect states; these could be identified in agreement with previous data from photoemission studies on rutile and anatase single crystals. From UPS, a valence-band width of ∼4.6 eV was determined for the nanocrystalline anatase films.



      A. Orendorz, J. Wüsten, C. Ziegler, H. Gnaser
      Applied Surface Science 252, pp. 85-88
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    29. (2005) Pd-PVP colloid as catalyst for Heck and carbonylation reactions: TEM and XPS studies

      Pd-PVP colloid (stabilized with polyvinylpyrrolidone) with a diameter of 19.8 nm in [Bu4N]Br medium catalyzes Heck coupling of bromobenzene with butyl acrylate and methoxycarbonylation of iodobenzene reactions. Oxidative addition of PhI or PhBr to Pd-PVP as the first step of a catalytic reaction was confirmed by TEM and XPS measurements. TEM studies showed significant reduction of Pd nanoparticle size after their reaction with PhX (X = I, Br) and [Bu4N]X (X = Cl, Br, I). The biggest shift of the center of nanoparticle size distribution, from 19.8 nm to 7.6 nm, was found when Pd-PVP reacted with PhI and [Bu4N]Br. The formation of [Bu4N]2[Pd(Ph)Br3]- and [Bu4N]2[PdBr4]-type complexes in that system was evidenced by XPS and UV–vis spectra.



      A. Gniewek, A. M. Trzeciak, J.J. Ziolkowski, L. Kepinski, J. Wrzyszcz, W. Tylus
      Journal of Catalysis 229 (2), pp. 332-343
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    30. (2005) Three-dimensional atomic-image reconstruction from a single-energy Si(001) photoelectron hologram

      We propose a new algorithm to achieve a very precise investigation of the three-dimensional atomic nucleus position in a material by the electron holography technique [T. Matsushita, A. Agui, Y. Yoshigoe, Europhys. Lett. 65 (2004) 207]. The algorithm is based on the “scattering pattern matrix” and an iterative gradient method, and it enables three-dimensional atomic-image reconstruction from a single-energy hologram. We measured a single-energy Si(0 0 1) photoelectron hologram of Si 2s emission using an Al Kα light source, and reconstructed the bulk structure with the use of the algorithm. We succeeded in locating as many as 29 atoms. The accuracy of the position for most atoms is within 0.05 nm.



      T. Matsushita, A. Agui, A. Yoshigoe
      Journal of Electron Spectroscopy and Related Phenomena 144-147, pp. 1175-1177
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    31. (2004) Argon Nanobubbles in Al(111): A Photoemission Study

      Two fundamental manifestations of Al conduction electron response to Ar atom core hole in the final state of photoemission have been studied in implanted Ar bubbles in Al(111). Ar 2p binding energy and the Doniach-Šunjić asymmetry of the core-level line shape vary systematically as functions of Ar+ implantation energy and number of ions bombarded (fluence). The observations are explained by relating the strength of Al conduction electron screening to the size of the Ar nanobubbles.



      C. Biswas, A. K. Shukla, S. Banik, S. R. Barman, A. Chakrabarti
      Phys. Rev. Lett. 92 (11), pp. 115506-1 - 115506-4
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    32. (2004) Epitaxial CuInS2 on Si(111) using di-tert-butyl disulfide as sulphur precursor

      In a new approach, we introduce a combination of chemical (CBE) and molecular beam epitaxy (MBE) of CuInS2 (CIS) on hydrogen-terminated Si(111) using di-tert-butyl disulfide (TBDS) as sulphur precursor. The films are analysed in situ with photoelectron spectroscopy and low-energy electron diffraction (LEED). Ex situ, the samples are investigated with X-ray diffraction (XRD) and scanning electron microscopy (SEM). We find that, at growth temperatures of 300 °C, no carbon is incorporated into the deposited film. Furthermore, on the In-rich side of the CuInS2 preparation, we additionally observe Cu2In. However, the valence band structure remains that of a typical CuInS2 film. During the growth in the Cu-rich regime, segregation of Cu2S occurs which can be identified by the shifting of the valence band edge towards the Fermi level. Epitaxial growth of CuInS2 is assumed for both regimes. LEED patterns and XRD data support the epitaxial relation Si{111}∣∣CuInS2{112}.



      W. Calvet, C. Lehmann, T. Plake, C. Pettenkofer
      Thin Solid Films 480-481, pp. 347-351
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    33. (2004) Microwave plasma in preparation of new membranes

      The presented paper is a peer-review of plasma action on porous polymer membranes. Considering the plasma medium the discussion is split in two parts: i) the first shows some effects caused by action of non-polymerizing gases, i.e. polymer etching and/or alteration of surface character, and, ii) the second covers action of plasma reagents resulted in the deposition of polymer layers. The authors' attention is focused mainly on alteration of the membranepore structure and surfaces character. Both kinds of plasma can turn porous membrane to new porous species with different surface character and pore size. It is possible also to prepare solid membranes where deposited polymer completely plugs the pores. The presented discussion is illustrated by the results of the authors' own research on preparation of brand-new polymer membranes.



      M. Bryjak, G. Pozniak, I. Gancarz, W. Tylus
      Desalination 163 (1-3), pp. 231-238
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    34. (2004) Effect of Pd or Ag additive on the activity and stability of monolithic LaCoO3 perovskites for catalytic combustion of methane

      The LaCoO3 perovskite-type catalysts in this study were monoliths resting on supports made of heat-resisting foil and washcoated with Al2O3. The La0.9Ag0.1CoO3 or La0.92Pd0.08CoO3 perovskite was used as the active phase. Partial substitution of lanthanum in the LaCoO3 perovskite with palladium or silver enhances the activity of the monolithic catalysts in the combustion of methane. XPS and XRD analyses show that during approximately 500 h on stream (at 750 and 704 °C, respectively) the surface composition of the La0.9Ag0.1CoO3 catalyst and that of the La0.92Pd0.08CoO3 catalyst undergoes considerable changes. In both the catalysts, cobalt and aluminum oxide segregate to the surface while the amount of carbonate groups decreases. In the La0.92Pd0.08CoO3 catalyst, the amount of palladium and the average oxidation state of Pd on the surface increase. On the surface of the La0.9Ag0.1CoO3 catalyst, the amount of silver decreases, and Ag in the metallic state oxidizes to Ag+, which probably becomes built-in the perovskite structure. In spite of these changes, the catalysts display a high activity and a good stability during above 500 h of methane combustion.



      B. Kucharczyk, W. Tylus
      Catalysis Today 90 (1-2), pp. 121-126
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    35. (2004) XPS study of oxidation of rhenium metal on γ-Al2O3 support

      The oxidation of Re/γ-Al2O3 catalysts, containing 1 and 10 wt% of rhenium, sintered in hydrogen was examined in the temperature range of 20–800 °C. The structures of the catalysts were investigated by XPS spectroscopy, TEM, and O2 uptake measurements. The low-loaded catalyst comprises metallic particles with sizes of 1–4 nm (dav=2.1 nm), while the high-loaded catalyst comprises particles with sizes of 1–9 nm (dav=4.9 nm). Even short exposure to air at room temperature causes complete oxidation of small clusters of metallic Re, while larger particles are covered with very thin ReOx skin (undetected by TEM). XPS shows that the high-loaded catalyst still contains 94.5% of metallic Re, while the low-loaded catalyst contains only 60.5%. The remaining part of the Re is oxidized to Re4+, Re6+, and Re7+ species. Oxidation at 150 °C causes enhanced formation of Re4+–Re7+ species and the amount of metallic Re quickly decreases to 33 and 2% for high- and low-loaded catalysts, respectively. This indicates a high affinity of the highly dispersed Re to oxygen. At this temperature, the Re/Al atomic ratio increases 2–4 times, indicating a large spreading of the oxide species on the support surface. Simultaneously, the average size of Re particles decreased as determined by TEM. At 300 °C, whole Re was oxidized mainly to Re2O7, though some amount to Re4+ and Re6+ species remained. The O2 uptake measurements confirm oxidation of rhenium particles. For the high-loaded catalyst O2 uptake attained a maximum level (O/Re=3.3) already at 300 °C, while for the low-loaded catalyst even at 500 °C the uptake (O/Re=2.98) is below the maximum level. XPS data showed, however, that at 500 °C, oxidation of rhenium to Re2O7 occurs for both catalysts. The Re/Al atomic ratio remains nearly constant after oxidation of both catalysts at 300–800 °C, indicating that Re7+ species are firmly bonded to alumina surfaces even at 800 °C. A detailed mechanism of oxidation of Re particles with different sizes is proposed based on a quantitative analysis of the XPS, O2 uptake, TEM, and previous Raman results.



      J. Okal, W. Tylus, L. Kepinski
      Journal of Catalysis 225 (2), pp. 498-509
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    36. (2004) Co-adsorption of CO and Pb on Pd(1 1 0)

      The adsorption of Pb on Pd ( 1 1 0)and co-adsorption with CO have been studied by photoemission spectroscopy and low energy electron diffraction. Two ordered structures are formed at sub-monolayer coverages of Pb with symmetry c(2×2) and (3×1). The valence band and Pd 3d core level spectra indicate a strong chemical interaction between Pb and Pd, and the formation of intermetallic bonds with both the first and second layer of Pd. The heat of CO adsorption on the c(2×2) phase is reduced to about half of the value on clean Pd, and even less on the (3×1) structure so that CO does not adsorb at a temperature of 120 K. Structural models are proposed for both of these phases based on the photoemission and co-adsorption results. The results confirm that the de-activation by Pb of Pd as a CO oxidation catalyst is due to the formation of an intermetallic compound, which drastically lowers the adsorption energy. However even the formation of a sub-monolayer phase is sufficient to radically alter the catalytic properties, and the formation of a bulk intermetallic is not necessary.



      N. Tsud, V. Dudr, S. Fabík, C. Brun, V. Cháb, V. Matolín , K. C. Prince
      Surface Science 560 (1-3), pp. 259-268
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    37. (2004) Resonant photoemission in Cr silicide at the absorption energy Cr 2p

      Valence band photoemission has been measured in chromium silicide as a function of the photon energy near the Cr 2p3/2 absorption threshold. Evidence of resonant photoemission is observed for the 3d valence band and the two-hole satellite. The threshold for normal Auger regime is 2.8 eV below the absorption peak and 0.8 eV below the Cr 2p3/2 binding energy, even lower than in pure Cr metal where it is already at extreme levels. The requirement for good resolution in photon energy relative to absorption width for the resonant Raman Auger to be observed is found to be less restrictive than expected.



      L. Galán, M. García, J. M. Ripalda, I. Montero, E. Román, D. R. Batchelor, P. R. Bressler
      Appl. Phys. Lett. 84, 4433
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    38. (2004) Photoemission study of two dimensional phase transitions on the Pb/Si(1 1 1) surface

      We have studied the low coverage, reconstructed phases of the Pb/Si(1 1 1) adsorption system by photoelectron spectroscopy. With decreasing coverage from 1.3 ML, the top of the valence band shows a transition from a metallic surface to a semiconducting surface, which is stable below a coverage of 0.2 ML. The Pb 5d core level was fitted by one symmetric peak for coverage from 0.1 to 0.2 ML without any observable shift. This state corresponds to Pb adatoms in a two dimensional surface alloy with Si where both atoms are located in the T4 position, and the surface reconstruction is (√3×√3)R30°. The peak energy and profile are independent of the relative Pb and Si adatom concentrations in the surface. For higher coverages we observe a varying width of the Pb 5d core level due to the appearance of an extra state shifted by about 0.4 eV; the results are consistent with information from STM images. Core level shifts of the Si 2p level are also reported.



      V. Dudr, N. Tsud, S. Fabík, B. Ressel, M. Vondrácek, K. C. Prince, V. Matolín, V. Cháb
      Surface Science 566-568, Part 2, pp. 804-809
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    39. (2004) Photoelectron spectroscopy on Pt atoms and clusters deposited on C(0001)

      An experimental photoelectron spectroscopy study is presented highlighting several aspects of importance for the study of deposited metal clusters and particles with photoemission. It is shown that the Fermi level is the correct energy reference for the core level binding energies. The choice of different deposition conditions, well within the range of soft landing, has a strong impact on the outcome of the spectroscopic experiments. Single adatoms as well as clusters deposited with some excess energy display relatively narrow core level spectra at much lower binding energies than previously reported, even when atomic mass selection is not performed. In contrast, single sized Pt19 clusters, deposited onto a thin Ar film before being exposed to the graphite surface show spectral broadening and shifts to higher binding energies. We discuss our results in terms of the cluster substrate interaction and the influence of deposition conditions on the metal adsorbate structure.



      K. Fauth, N. Schneider, M. Heßler, G. Schütz
      Eur. Phys. J., D 29, pp. 57-61
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    40. (2004) Pd-based monolithic catalysts on metal supports for catalytic combustion of methane

      Monolithic Pd-based catalysts on heat-resisting foil supports, with different washcoats, were investigated for catalytic activity in the combustion of methane. Palladium was deposited either onto pure aluminium oxide (Pd/Al2O3) or onto Al2O3 modified with 9 wt.% of SiO2 and 0.8 wt.% of La2O3 (Pd/Al2O3-SiO2) or with ZrSiO4 (Pd/Al2O3-ZrSiO4). The modification of the Al2O3 washcoats was found to increase the conversion of methane and to enhance the thermal resistance of the catalysts. XPS, XRD and TEM examinations have shown that PdO well dispersed on the washcoat surfaces is the active form of palladium in the Pd/Al2O3, Pd/Al2O3-SiO2 and Pd/Al2O3-ZrSiO4 catalysts. XPS examinations of the same catalysts after 20-h run have revealed an over twofold increase in surface Pd concentration measured in terms of the Pd/Al ratio, which substantiates an activation of the catalysts. Heating to 1060 °C deactivated all the catalysts due to the agglomeration of crystallites on their surfaces and decomposition of PdO to metallic Pd. The incorporation of additives into the pure Al2O3 washcoat noticeably reduced crystallite growth at high temperatures. As a result, the deactivation of the Pd/Al2O3-ZrSiO4 and Pd/Al2O3-SiO2 catalysts was much lower than that of the Pd/Al2O3 catalyst.



      B. Kucharczyk , W. Tylus, L. Kepinski
      Applied Catalysis B: Environmental 49 (1), pp. 27-37
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    41. (2004) Combined high-pressure cell-ultrahigh vacuum system for fast testing of model metal alloy catalysts using scanning mass

      An apparatus for fabrication, surface analysis in ultrahigh vacuum, and testing of the catalytic activity of model metal alloy catalysts is described. Arrays of model catalysts are produced by electron-beam deposition of up to four metals simultaneously onto a substrate. The surface analysis techniques available are scanning electron microscopy, x-ray photoemission spectroscopy, ion scattering spectroscopy, Auger electron spectroscopy, sputter profiling, and temperature programmed desorption. The catalytic activity of the model catalysts is tested individually by scanning a combined gas delivery and gas sampling device over the sample surface. The gas sampled is analyzed with mass spectrometry. Experiments can be made at pressures up to 1 bar and temperatures up to 500 °C. It is shown that the lateral resolution is better than 0.2 mm and that up to 20 circular spots, 1 mm in diameter, can be studied on a substrate 10 mm in diameter. A high pressure cell with an all-metal sealed ultrahigh vacuum lock is also described as part of the work.



      M. Johansson, J. Hoffmann Jørgensen, I. Chorkendorff
      Review of Scientific Instruments 75, 2082
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    42. (2004) A new approach for three-dimensional atomic-image reconstruction from a single-energy photoelectron hologram

      A "scattering pattern matrix" method is proposed here to overcome the difficulties presented by photoelectron holography, such as forward-scattering and multi-energy problems. This method makes it possible to reconstruct a three-dimensional atomic arrangement from a single-energy hologram. We have utilized the "scattering pattern matrix" that includes the angular variation of the scattered object waves, and we have adopted a special average process and the gradient projection method for minimizing the mean-squared error. The reconstruction of the Si bulk structure is demonstrated by using an experimental Si(111) 2s single-energy hologram. The holographic reconstruction provided a three-dimensional image with a size of 10 Å along both the vertical and horizontal axes.



      T. Matsushita, A. Agui, A. Yoshigoe
      Urophys. Lett. 65 (2), pp. 207-213
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    43. (2004) The influence of surface defects on methanol decomposition on Pd(111) studied by XPS and PM-IRAS

      Methanol adsorption/desorption and its time- and temperature-dependent decomposition on well-annealed and defect-rich (ion-bombarded) Pd(1 1 1) were examined by X-ray photoelectron spectroscopy (XPS) and polarization-modulation infrared reflection absorption spectroscopy (PM-IRAS). Annealing CH3OH multilayers from 100 to 700 K mainly resulted in CH3OH desorption. Dehydrogenation to CO was a minor path and only trace amounts of carbon or carbonaceous species (CHx; x=0–3) were produced, i.e. C–O bond scission was very limited. By contrast, an exposure of 5 × 10−7 mbar CH3OH at 300 K produced CHx (∼0.3 ML) on both surfaces but the rate of formation was not considerably enhanced by surface defects. On well-annealed Pd(1 1 1) isolated carbon atoms were identified by XPS in the early stages of carbon deposition, with carbon diffusion leading to the growth of carbon clusters in the later stages. Since carbon(aceous) species may either originate from C–O bond scission within methanol (or CHxO) or from a consecutive dissociation of the dehydrogenation product CO, analogous experiments were also carried out with CO. PM-IRAS spectra up to 170 mbar CO, acquired using a UHV-high-pressure cell, did not show any indications of CO dissociation, excluding CO as source of carbonaceous deposits.



      O. Rodríguez de la Fuente, M. Borasio, P. Galletto, G. Rupprechter, H.-J. Freund
      Surface Science 566-568, Part 2, pp. 740-745
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    44. (2004) Synchrotron photoemission spectroscopy study of ammonium hydroxide etching to prepare well-ordered GaAs(1 0 0) surfaces

      Synchrotron-induced photoelectron spectroscopy was used to investigate the native-oxide-covered GaAs(1 0 0) surface and changes induced by etching with aqueous ammonia solution and by annealing in vacuum. The etching step removes arsenic and gallium oxides from the surface and the surface gets covered by elemental arsenic and tiny amounts of gallium suboxide. The surface oxygen content is reduced by an order of magnitude after etching, whereas the surface carbon content is somewhat increased. Annealing of this surface at 450 °C results in the disappearance of elemental arsenic and a considerable decrease in surface carbon and oxygen contents. The valence band spectra exhibit clear features typical for As-terminated GaAs(1 0 0) surfaces, as also obtained after As decapping.



      M. V. Lebedev, D. Ensling, R. Hunger, T. Mayer, W. Jaegermann
      Applied Surface Science 229 (1-4), pp. 226-232
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    45. (2004) Surface localized nitrogen incorporation in epitaxial FePd films and its effect in the Magneto-Optical properties

      In situ exposure of FePd chemically disordered alloys to a N plasma prior to capping layer deposition produces a nitridation localized on the topmost 20 Å alloy region. In this region, a N–Fe bond prevails over the N–Pd. From the structural point of view, this nitridation does not induce relevant modifications on the lattice parameters compared with non-nitrided samples of equivalent composition, being only slightly modified in the alloys with higher Fe concentration. From the magnetic point of view, nitrogen incorporation induces a reduction or even a loss of the ferromagnetism of the nitrided FePd region, giving rise to a global decrease in the polar Magneto-Optical Kerr response in a wide spectral range due to the increase of the effective thickness of the non-magnetic capping layer.



      M. S. Martin-González, Y. Huttel, A. Cebollada, G. Armelles, F. Briones
      Surface Science 571 (1-3), pp. 63-73
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    46. (2003) Vibrational structure in C 1s photoelectron spectra of ethylene on the Si(1 0 0)(2 × 1) Surface

      We have investigated the C 1s photoelectron spectra of ethylene on the Si(1 0 0)(2 × 1) surface, using high resolution photoelectron spectroscopy. The vibrational structure has been observed in the C 1s spectra where the C–H stretching mode is dominant. The vibrational splittings of C 1s ionized state are very similar to those in the ground state. It is found that linear coupling model is applicable in this system and this excitation process is a Frank–Condon process. The curvature of potential energy surface of C–H and C–D bond is almost unchanged upon core ionization.



      Y. Yamashita, S. Machida, M. Nagao, S. Yamamoto, K. Mukai, J. Yoshinobu
      Chemical Physics Letters 374 (5-6), pp. 476-481
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    47. (2003) Effect of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane surface modification and C.I. Acid Red 18 dye adsorption on the physicochemical properties of silica precipitated in an emulsion route, used as a pigment and a filler in acrylic paints

      Studies were performed on the synthesis of spherical silica particles in an emulsion route, and its surface modification using N-2-(aminoethyl)-3-aminopopyltrimethoxysilane. Onto the aminosilane-treated silica surface, C.I. Acid Red 18 dye was adsorbed. The ensuing silica and its derivatives were subjected to comprehensive physicochemical and dispersion analysis. Both the size and shape of the particles were estimated and the surface specific area (BET) and porosity were characterised using adsorption/desorption curves. Moreover, chemical and surface compositions were determined using elemental analysis and XPS. A mechanism was suggested for the interaction betweeen the aminosilane-modified silica and an organic dye. The obtained pigment was tested in an acrylic paint system; the precipitated monodisperse silica was found to exhibit optimum properties as a carrier of organic dye, particularly after modification of the former with aminosilane, thus acting as a valuable filler and pigment in modern paint systems.



      T. Jesionowski, M. Pokora, W. Tylus, A. Dec, A. Krysztafkiewicz
      Dyes and Pigments 57 (1), pp. 29-41
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    48. (2003) Electronic states and chemical reactivity of Si(100)c(4x2) surface at low temperature studied by high resolution Si 2p core level photoelectron spectroscopy

      We have investigated the electronic states of clean and BF3 adsorbed Si(1 0 0) surfaces at low temperature by means of high resolution Si 2p photoelectron spectroscopy. The peak intensities of upper atom and lower atom of the asymmetric dimer in Si 2p spectra do not change even at 30 K compared with those at higher temperature up to 300 K, indicating that the dimer is asymmetric in the ground state. In order to investigate chemical reactivity of asymmetric dimer on Si(1 0 0), a typical Lewis acid molecule BF3 is adsorbed on Si(1 0 0). We have found that BF3 molecules are dissociated into BF2 and F on Si(1 0 0) and dissociated species (BF2 and F) are adsorbed predominantly on the up dimer atoms of the asymmetric dimers.



      S. Machida, M. Nagao, Y. Yamamoto, Y. Kakefuda, K. Mukai, Y. Yamashita, J. Yoshinobu
      Surface Science 532-535, pp. 716-720
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    49. (2003) Plasmons in core-level photoemission spectra of AI(111)

      The line shape and intensity of surface and bulk plasmon excitations in Al 2s and 2p core-level spectra of Al(111) have been studied as functions of the photoelectron emission angle (θ). For both surface and bulk plasmons, an asymmetric line shape is observed in normal emission, which becomes more symmetric in grazing emission. The asymmetric line shape is in good agreement with theory. The relative contributions of the intrinsic, extrinsic, and interference processes to the surface plasmon intensity are determined from its variation with θ and from theoretical line-shape calculations. We show the importance of the interference process in determining the intensity and line shape of the plasmons. From the intensity variation of multiple (n=1–6) bulk plasmons (nωp) with n, the intrinsic and extrinsic bulk plasmon probabilities are determined.



      C. Biswas, A. K. Shukla, S. Banik, V. K. Ahire, and S. R. Barman
      Physical Review B 67, 165416
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    50. (2003) Plasma modified polymers as a support for enzyme immobilization. Pt. 1. Allyl alcohol plasma

      The paper describes deposition of plasma polymerized allyl alcohol on polysulfone film. It is shown that film surface becomes more hydrophilic after plasma treatment independently on presence of argon in a reaction mixture. The chemistry of the new surface layer was established by FTIR-ATR and ESCA spectroscopy. The substrate placed close to the plasma edge was the most hydrophilic but the amount of hydoxyl groups was not the highest there. Presence of argon stabilized the plasma but the deposited layer contained relatively less oxygen-bearing functionalities. The plasma treated polymer was subjected to xylose isomerase immobilization. For this purpose the divinylsulfone method was adapted. The studies revealed no correlation between the surface hydrophilicity and efficiency of immobilization.



      I. Gancarz, J. Bryjak, M. Bryjak, G. Poźniak, W. Tylus
      European Polymer Journal 39 (8), pp. 1615-1622
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    51. (2003) Plasma modified polymers as a support for enzyme immobilization II. Amines plasma

      Polysulfone films were modified by ammonia, n-butylamine and allylamine remote plasma using various sample-to-plasma distances. Contact angle measurements, FTIR-ATR and XPS spectroscopy proved the presence of polar, including amine, groups on the modified surface. Presence of argon in the plasma environment made the plasma more stable and in most cases left the surface more hydrophilic but with a lower amount of nitrogen moieties on it. Glucose isomerase was successfully immobilized on the plasma-treated samples. Its activity correlates well with the concentration of C–N bonds on the surface. The highest enzyme activity was achieved for samples treated with allylamine/Ar plasma close to the plasma edge.



      I. Gancarz, J. Bryjak, G. Pozniak, W. Tylus
      European Polymer Journal 39 (11), pp. 2217-2224
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    52. (2003) Physicochemical and morphological properties of hydrated silicas precipitated following alkoxysilane surface modification

      Modified silicas were obtained by precipitation from aqueous solutions of sodium metasilicate and sulphuric acid. For the modification, silane coupling agents with various functional groups were applied, including aminosilane (AEAPTS), glycidoxysilane (GPTS), mercaptosilane (McPTS), and vinylsilane (VTMES). Extensive physicochemical evaluation of the obtained modified silicas was conducted, using FTIR, CP MAS NMR and XPS techniques. The silica surface modification was proven to depend upon chemical reactions and to show intensity increasing with a rising concentration of a given modifier. A surface charge of the formed silica dispersions was also examined, by determining their zeta potential. Moreover, surface morphology, dispersion and particle size of the obtained silicas were evaluated, employing TEM electron microscopy and the technique of a dynamic light scattering (DLS). The studies demonstrated that application of hydrophobic type silanes for surface modification of the hydrated silicas restricted the intense tendency for agglomeration in the formed precipitated silicas.



      T. Jesionowski, J. Zurawska, A. Krysztafkiewicz, M. Pokora, D. Waszak, W. Tylus
      Applied Surface Science 205 (1-4), pp. 212-224
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    53. (2003) Interfacial reconstruction in the system Pb/Ag(110)

      We have examined the Pb/Ag(1 1 0) adsorption system using low energy electron diffraction (LEED) and synchrotron radiation X-ray photoemission spectroscopy (SRXPS). At a temperature of 120 K, layer-by-layer growth occurs and no superstructure is observed by LEED. On heating a two monolayer film to 230 K, or on deposition of two monolayers at 300 K temperature, a c(2 × 4) superstructure is observed. We interpret this as a reconstruction involving a (1 × 2) Ag substrate, and a buckled hexagonal overlayer of Pb. The reconstruction is unusual as it is induced at a solid–solid interface, rather than by an adsorbate at the solid–vacuum interface. Core level shifts of the Pb 5d and 4f and Ag 3d levels are also reported.



      N. Tsud, S. Fabík, V. Dudr, M. Vondrácek, V. Cháb, V. Matolín, K. C. Prince
      Surface Science 542 (1-2), pp. 112-119
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    54. (2003) Strong influence of defects on the electronic structure of Pt adatoms and clusters on graphite

      We study the specific impact of defects such as step edges at the graphite surface on the electronic configuration of adsorbed Pt atoms and Pt8 clusters. Surface diffusion is strongly reduced by depositing Pt and Pt8 into a thin rare gas layer. In this configuration a very narrow adatom Pt 4f spectrum is found at an exceptionally small binding energy, similar to Pt surfaces. Both, adatom and cluster spectra are strongly shifted towards higher binding energy when allowed to diffuse towards defects like step edges. The strong shifts are indicative of a chemical reaction at the step edges and are conjectured to be part of the particle size dependent binding energy shifts typically observed for transition metal clusters grown on the surface of graphite.



      K. Fauth, M. Heßler, D. Batchelor, G. Schütz
      Surface Science 529 (3), pp. 397-402
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    55. (2003) A search for reason for deactivation of alkylation iron catalyst

      Deactivation of the iron catalyst Fe-Si-Cr-K-O was investigated with the help of X-ray photoelectron spectroscopy and checked in reaction of phenol alkylation with methanol performed in gas phase at the atmospheric pressure. It was indicated that the catalytic action of the alkylation catalyst (active–inactive) could be correlated with the relative contribution of the oxidation states of iron (+2) and (+3). The intensity ratio of the Fe 3p individual components was found to be a good measure of the contribution. The catalyst as-prepared has the (+2)/(+3) ratio 1.7, active in reaction—1.9, calcined at 1000 °C—1.4 and deactivated during the reaction—2.7. The process accompanied other reasons for deactivation as carbon deposition on the surface and/or sintering of catalyst crystallites.



      H. Grabowska, R. Klimkiewicz, W. Tylus and P. J. Godowski
      Applied Catalysis A: General 240 (1-2), pp .111-117
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    56. (2003) Oxidation and redispersion of a low-loaded Re/ γ-Al2O3 catalys

      The interaction of sintered low-loaded Re/γ-Al2O3 catalysts with oxygen has been studied over a wide temperature range, 20–800 °C. The structure of the catalyst was characterized using different techniques: H2 chemisorption, O2 uptake, BET, TEM, and also by Raman and XPS spectroscopy. In the catalyst reduced in H2 at 800 °C, Re is present as a nonuniform phase consisting of metallic particles with sizes of 1–4 nm and a certain amount of very small clusters (below 1 nm) undetectable by TEM. Oxidation at room temperature causes dissociative chemisorption of oxygen on rhenium with possible formation of a superficial oxide on the Re particles and complete oxidation of the clusters to Re4+–Re7+ species. After oxidation at 150 °C only 2% of total Re remains in the reduced state which implies high affinity of highly dispersed Re to oxygen. At 200–300 °C, oxidation of Re hastens giving a mixture of Re4+, Re6+, and Re7+ ions, while at 500 °C, complete oxidation to Re2O7 occurs. At elevated temperatures, Re2O7 sublimates and instantaneously adsorbs on γ-alumina surface as monomeric ReO4 species. At 500–800 °C, these species are strongly bound to alumina forming a kind of a surface compound with an Al–O–ReO3 structure. This accounts for the low loss of Re observed even at 800 °C. Redispersion of rhenium was observed after a mild H2 treatment of the oxidized rhenium catalyst.



      J. Okal, L. Kepinski, L. Krajczyk, W. Tylus
      Journal of Catalysis 219 (2), pp. 362-371
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    57. (2003) Sorption of aurocyanide and tetrachloroaurate onto resin with guanidine ligand-an XPS approach

      The guanidine ligand attached to vinylbenzyl chloride matrix as well as its sorption ability to tetrachloroaurate and dicyanoaurate ions were investigated upon using X-ray photoelectron spectroscopy. The form of metallic gold, Au(0), was not observed on gold loaded resin surface when solutions of tetrachloroaurate or potassium dicyanoaurate were used. Complete elution of gold was achieved for both regeneration media: thiourea solution and mixture of sodium hydroxide and benzoate. The results demonstrate that XPS can also be a powerful technique for the analysis of the oxidation state of sorbed metal and can be a suitable method for the confirmation of functional groups incorporated in the polymer.



      D. Jermakowicz-Bartkowiak, B. N. Kolarz, W. Tylus
      Polymer 44 (19), pp. 5797-5802
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    58. (2002) Modification of polysulfone membranes 4. Ammonia plasma treatment

      The effect of NH3 and NH3/Ar plasma on ultrafiltration polysulfone membranes have been studied. Results of contact angle, FTIR–ATR and X-ray photoelectron spectroscopy experiments clearly showed that both plasmas introduced hydrophilic, nitrogen- and oxygen-containing moieties on the polymer surface and that NH3/Ar plasma was more efficient. That plasma was also more aggressive––signs of strong etching could be seen on the SEM pictures. Redeposition of etched material seemed to take place inside the pores. On the contrary, ammonia plasma was soft and caused cleaning the surface and pores enlargement. Performance of ammonia plasma modified membranes was greatly improved and independent on solution pH. The last observation proved amphoteric character of the surface. NH3/Ar plasma treatment gave membranes of acidic surface and filtration indices not so good as for ammonia plasma.



      M. Bryjak, I. Gancarz, G. Pozniak, W. Tylus
      European Polymer Journal 38 (4), pp. 717-726
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    59. (2002) N-butylamine plasma modifying ultrafiltration polysulfone membranes

      Some properties of ultrafiltration polysulfone membranes modified with n-BuNH2 and n-BuNH2/Ar plasmas were studied. Contact angle measurements, XPS and SEM were used to characterize the surface changes. Pore size estimation, water transport and filtration parameters helped to describe changes in filtration performance. Presence of argon in plasma environment stabilized plasma but made it more aggressive; pore size increased and surface etching took place. This plasma grafted a smaller number of nitrogen features — most of them in the form of amine. Excellent filtration performance was observed for BuNH2/Ar plasma-modified membranes in an acidic environment.



      G. Pozniak, I. Gancarz, M. Bryjak, W. Tylus,
      Desalination 146 (1-3), pp. 293-299
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    60. (2002) Modification of polysulfone membranes 5. Effect of n-butylamine and allylamine plasma

      This paper describes some properties of microwave plasma polymers of n-butylamine and allylamine deposited on the surface of polysulfone substrate. Contact angle evaluation, ATR-FTIR spectroscopy, X-ray photoelectron spectroscopy analysis and estimation of pore size distribution of ultrafiltration polysulfone membranes were used. It was found that addition of Ar to the amine vapor significantly stabilized the plasma and converted it to the ablation mode. The surface became more hydrophilic and the surface groups were enriched in oxygen. Both amines gave deposits of various compositions: the n-butylamine polymer was not as enriched in amines as the polymer formed from allylamine. However, the amounts of nitrogen in both deposits indicated allylamine to be the precursor for the preparation of membranes with weakly basic functionalities. When porous membranes are modified, the ultrafilters obtained may be named `fouling protected' as they do not foul so intensively with proteins as their unmodified analogues. To a lesser extent, similar behavior was shown by membranes modified by deposition of plasma-polymerized n-butylamine.



      I. Gancarz, G. Pozniak, M. Bryjak, W. Tylus,
      European Polymer Journal 38 (10), pp. 1937-1946
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