| 1. |
- Jaworowski, AJ, et al.
(författare)
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CO dissociation on Mo(110) studied by high-resolution core-level spectroscopy
- 2001
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Ingår i: SURFACE SCIENCE. - : ELSEVIER SCIENCE BV. - 0039-6028. ; 492:1-2, s. 185-194
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the CO/Mo(1 1 0) adsorption system at different sample temperatures by high-resolution core-level spectroscopy and near-edge X-ray-absorption fine-structure measurements. We demonstrate that CO molecules having different tilt angles with r
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| 2. |
- Jaworowski, AJ, et al.
(författare)
-
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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| 3. |
- Sandell, Anders, et al.
(författare)
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Geometric and electronic structure of PdMn bimetallic systems on Pd(100)
- 2002
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121 .- 1550-235X. ; 65:3
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Tidskriftsartikel (refereegranskat)abstract
- An experimental and theoretical study of PdMn bimetallic systems formed on Pd(100) is presented. It is shown that a flat Mn monolayer can be formed at 90 K. A comparison of calculated Mn 3d density-of-states and experimental valence photoemission and x-ray-absorption results suggests that the monolayer is antiferromagnetic, in line with earlier predictions. A similar comparison for the Pd(100)-Mn-c(2 X 2) alloy formed after annealing to 570 K suggests a two-layer-thick alloy consisting of Pd and Mn atoms arranged in a checkerboard pattern. Core level photoemission results are consistent with this conjecture in that three different types of Pd atoms bonded to Mn atoms are found. Total energy calculations demonstrate, however, that a Pd-capped Cu3Au structure is energetically more favorable, but the system is not able to reach this state at the used annealing temperature. Kinetic thresholds must be overcome by heating and this is shown by the experimental trend in which the Mn atoms are situated at the surface at lower temperatures. Relaxation effects were also calculated and the surface layer of the PdMn-terminated c(2 X 2) alloy was found to be buckled with the Pd atoms situated above the Mn atoms, in quantitative agreement with a previous low-energy electron diffraction study.
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| 4. |
- Sandell, Anders, et al.
(författare)
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Surface chemistry of TiCl4 on clean and hydrogen modified W(110): identification of surface intermediates
- 2002
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Ingår i: Surface Science. - 0039-6028. ; 521:3, s. 129-138
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption and decomposition of titanium tetrachloride (TiCl4) on W(110) were studied with high-resolution core level photoelectron spectroscopy. At least two stable intermediates are formed along the pathway to TiCl4 decomposition: TiCl4(a), which is stable up to 300 K, and TiCl3(a), which is stable up to 500 K. Successive adsorption at 80 K shows that the TiCl4() species forms in the presence of dissociated TiCl4 or hydrogen. This indicates that dissociative sites must be blocked before TiCl4 can adsorb intact.
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| 5. |
- Sandell, Anders, et al.
(författare)
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The Mn 2p core-level photoelectron spectrum of Pd-Mn bimetallic systems on Pd(100)
- 2004
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 135:1, s. 7-14
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that the Mn 2p spectra of Mn atoms in Pd-Mn bimetallic surface systems formed on Pd(1 0 0) exhibit a satellite, separated 1 eV from the main line, in addition to the 5 eV satellite previously observed for Mn-containing compounds and surface alloys. The main line and the low-energy satellite are both assigned to 2p(5)3d(6) final states whereas the 5 eV satellite is associated with 2p(5)3d(5) final states. The identification of the two low-binding energy peaks is based on ail energy comparison with the Mn 2p --> 3d X-ray absorption spectrum. The relative intensities of the two low-binding energy peaks furthermore vary depending on the Mn atomic environment, reflecting the changes in the properties of the Mn 3d band rather than the geometric position of the Mn atoms. For Mn coverages less than or equal to1 monolayer, the highest degree of Mn 3d localization was found for structures in which the Mn atoms are spread uniformly over the surface. The observed changes in the Mn 2p spectra are discussed in terms of varying Mn-Pd interaction, exchange splitting and magnetic ordering (C) 2003 Elsevier B.V. All rights reserved.
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