| 1. |
- Andersen, J. N., et al.
(författare)
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Alkali metal adsorption on Al(111)
- 1993
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 289:3, s. 307-334
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Tidskriftsartikel (refereegranskat)abstract
- The submonolayer adsorption of Na, K, Rb, and Cs on the Al(111) surface at 100 K and at room temperature is investigated by high resolution core level spectroscopy and low energy electron diffraction. It is found that the first alkali atoms on the surface adsorb at surface defects. At higher coverages, up to approximately one third of the maximum submonolayer coverage, alkali atoms adsorbed at defects coexist with a dispersed phase. At higher coverages island formation is found to occur for the majority of the systems. It is argued that all of the ordered structures formed at room temperature involve a disruption of the Al(111) surface in contrast to the situation at 100 K where the alkali atoms adsorb as adatoms.
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| 2. |
- Andersson, Martin, et al.
(författare)
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Anharmonic resonances in the C-H stretch region of ethoxy adsorbed on W(110): vibrational spectroscopy and calculations
- 2003
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Ingår i: Surface Science. - 0039-6028. ; 532-535, s. 221-226
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Tidskriftsartikel (refereegranskat)abstract
- We show that it is possible to understand and interpret the complex and rich C-H stretch region in the vibrational spectrum of ethoxy adsorbed on W(110) in terms of fundamental C-H stretch modes in Fermi resonance with C-H deformation overtones and combinations. The mode assignment is based on calculated C-13 isotopic shifts for an ethoxy-Cu-5 cluster. The coupling constants have been derived from calculated energy third derivatives of free ethanol and the coupling was implemented by an effective Hamiltonian matrix. The agreement with experiments is very good.
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| 3. |
- Borg, Mikael, et al.
(författare)
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Structure and formation of the Al(100)-(root 5 x root 5) R27 degrees-Na phase: a LEED, DFT and HRCLS study
- 2002
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Ingår i: Surface Science. - 0039-6028. ; 515:2-3, s. 267-280
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Tidskriftsartikel (refereegranskat)abstract
- Adsorption of 0.2 ML Na on Al(1 0 0) at room temperature yields a disordered Al(1 0 0)-(1 x 1)-Na phase, which transforms reversibly to a well-ordered Al(1 0 0)-(root5 x root5)R27degrees-Na phase on cooling below 250 K. Based on low energy electron diffraction (LEED) and high resolution core-level spectroscopy (HRCLS) measurements, and on ab initio calculations, it is concluded that the structure of the Al(1 0 0)-(root5 x root5-)R27degrees-Na phase consists of Na atoms occupying substitutional sites. The structural parameters obtained from LEED and density functional theory analyses are in quantitative agreement. Adsorption of 0.2 ML Na at 100 K yields an Al(1 0 0)-c(2 x 2)-Na island structure, which transforms irreversibly into the (root5 x root5)R27degrees-Na structure by annealing above 190 K. The nature of the reversible and irreversible phase transformations to the (root5 x root5)R27degrees structure is investigated by HRCLS and LEED. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 4. |
- Carlsson, Anna K, 1966, et al.
(författare)
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Oscillatory photoemission cross section for alkali monolayer quantum well states
- 1996
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 352-354, s. 656-659
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Tidskriftsartikel (refereegranskat)abstract
- A strong oscillatory photon energy dependence, observed in the photon energy range between 5 and 26 eV, for the intensity of photoemission peaks due to quantum well states in Na and Cs monolayers on Cu(111) is ascribed to interference between the contributions to the outgoing photoelectron wave from the two tails of the quantum well state.
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| 5. |
- Carlsson, A, et al.
(författare)
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Strain state in semiconductor quantum dots on surfaces : a comparison of electron microscopy and finite element calculations
- 1998
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Ingår i: Surface Science. - 0039-6028. ; 406:1-3, s. 48-56
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Tidskriftsartikel (refereegranskat)abstract
- The strain distribution in InP quantum dots, coherently grown on a GaInP substrate, was determined by image analysis of high-resolution electron microscopy images. Image simulations were used to verify the obtained results. The measured strain values were compared with values obtained from finite element calculations, using the dot shape determined by electron microscopy. The measured and calculated strain values are in good agreement, supporting the use of finite element calculations for strain determination in quantum dots.
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| 6. |
- Heskett, D., et al.
(författare)
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Alkali-alkali interactions on Al(111) : segregation and islanding in Na-Rb mixtures
- 1994
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Ingår i: Surface Science. - 0039-6028. ; 316:3, s. 303-308
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Tidskriftsartikel (refereegranskat)abstract
- The low temperature coadsorption of Na and Rb on an Al(111) surface is examined with a combination of LEED and core level photoemission spectroscopy. We observe LEED pattern sequences and alkali core level binding energies which are consistent with a net total alkali coverage and can be explained by Na-Rb repulsion, segregation, and islanding, though other models cannot be definitely excluded.
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| 7. |
- Jacobsen, SN, et al.
(författare)
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Sharp microfaceting of (001)-oriented cerium dioxide thin films and the effect of annealing on surface morphology
- 1999
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Ingår i: Surface Science. - 0039-6028. ; 429:1-3, s. 22-33
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Tidskriftsartikel (refereegranskat)abstract
- Cerium dioxide, CeO2, is a chemically stable oxygen-ion-conducting material, which has been extensively used as an additive or support in oxidation catalysts. The fact that catalytic behaviour is often surface structure sensitive and/or edge atom dependent suggests that different surfaces might be discernible in associated redox processes. Thus, it is desirable to realise CeO2 films with a well-defined microstructure and with crystallographically uniform surfaces. In this paper we present evidence of extremely sharp microfaceting on the surface of thin CeO2 films grown by r.f. magnetron sputtering, and the effect of annealing on the formed sharp ridges. The results show that nominally designated crystallographic surfaces may in fact not coincide with the surfaces exposed as-grown. Thus, there is a clear risk for erroneous interpretation of various orientation-dependent surface properties. Carefully controlled annealing of these films can be utilised as a method for tailoring the resulting surface morphology on the atomic scale.
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| 8. |
- Jaworowski, A. J., et al.
(författare)
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Adsorption sites in O and CO coadsorption phases on Rh(111) investigated by high-resolution core-level photoemission
- 1999
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Ingår i: Surface Science. - 0039-6028. ; 431:1, s. 33-41
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution core-level spectroscopy is used in combination with low-energy electron diffraction (LEED) and photoelectron diffraction to identify the adsorption sites for three different coadsorbed phases consisting of ordered overlayers of oxygen coadsorbed with CO on the Rh(111) single-crystal surface. The three ordered overlayer structures, which may be denoted as 2O + CO/Rh(111), O + CO/Rh(111) and O+2CO/Rh(111), all show (2 × 2) LEED patterns. In the 2O + CO and O + CO phases the CO molecules are found to occupy only on-top sites while the O + 2CO phase shows CO molecules in both on-top and three-fold hollow sites. In all cases the oxygen atoms are found in three-fold hollow sites. For the O + CO and O + 2CO phases our results confirm previous determinations by LEED, while the 2O + CO phase has not been observed before on Rh(111). The core-level binding energies of the C 1s and O 1s core levels for both adsorbates are characteristics of the adsorption site and are very close to the binding energies found for the pure cases of only oxygen or CO adsorbed on Rh(111). In the coadsorption phases we find that the interaction between the adsorbates has only a minor influence on the core-level binding energies. For the O + 2CO/Rh(111) coadsorption phase we find that a full CO coverage is not obtained; less than 80% of the unit cells contain two CO molecules, in line with previous findings.
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| 9. |
- Jaworowski, A J, et al.
(författare)
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Determination of NO adsorption sites on Pd(100) using core level photoemission and low energy electron diffraction
- 2002
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Ingår i: Surface Science. - 0039-6028. ; 501:1-2, s. 74-82
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of NO on Pd(1 0 0) is investigated with high resolution core level spectroscopy and low energy electron diffraction (LEED). Several ordered NO overlayers were observed, in agreement with earlier Studies. Our data clearly show that NO adsorbs in fourfold hollow sites at coverages tip to 0.25 -0.30 monolayer (ML) whereas at 0.5 ML only bridge sites are occupied. By a reinterpretation of previous electron energy loss spectroscopy (EELS) investigations we show that the new site assignments are in agreement the EELS data, Based on the photoemission results for the N 1s and the Pd 3d core levels we propose new structure models for the (2root2 x 2root2)R45degrees and the p(4 x 2) LEED patterns found at coverages of 0.5 and 0.25 ML, respectively. In the latter case, it is suggested that the p(4 x 2) LEED pattern is formed from domains having p(2 x 2)-NO and c(4 x 2)-2NO unit cells.
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| 10. |
- Jaworowski, AJ, et al.
(författare)
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Mn-induced NO dissociation on Pd(100)
- 2002
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Ingår i: Surface Science. - 0039-6028. ; 501:1-2, s. 83-92
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Tidskriftsartikel (refereegranskat)abstract
- The changes in the NO adsorption properties of Pd(1 0 0) due to the addition of Mn have been investigated using high resolution core level photoelectron spectroscopy. The Pd(1 0 0) surface was modified by forming a c(2 x 2)-PdMn surface alloy at two different Mn coverages, giving surfaces partly and fully alloyed, respectively, as shown by scanning tunneling microscopy. NO adsorption on the alloy films was found to destroy the c(2 x 2) structure. Dissociation of the NO molecules upon heating is observed, in stark contrast to NO on the clean Pd(1 0 0) surface from which all the molecules desorb intact upon heating. The dissociation process on the c(2 x 2)-PdMn-(1 x 1)-Pd mixed surface is completed at a significantly higher temperature than for the homogeneous c(2 x 2) surface. It is suggested that Mn atoms give rise to NO dissociation at lower temperatures. whereas Pd atoms situated at c(2 x 2)-(1 x 1) boundaries are responsible for the NO decomposition at higher temperatures.
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