Characterization And Properties Of The AIPdMn 5 Surface

Cappello, Giovanni; Déchelette, A.; Schmithüsen, Frank; Chevrier, J.; Comin, F.; Stierle, Andreas; Formoso, V.; Boissieu, M. de; Lograsso, Thomas A.; Jenks, Cynthia J.; Delaney, D.W.

doi:10.1557/proc-553-243

Cited by 10 publications

(15 citation statements)

References 9 publications

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“…[5,6,[9][10][11][12][13][14][15][16]] Dynamical LEED analysis of experimental intensity-voltage (IV) curves can then be used to derive atomic structure, but for quasicrystals a special challenge comes from the non-periodic ordering of the atoms in the bulk. (A number of techniques, including LEED, have confirmed that the fivefold surfaces retain fivefold symmetry.…”

Section: Introductionmentioning

confidence: 99%

Structural aspects of the fivefold quasicrystalline Al–Cu–Fe surface from STM and dynamical LEED studies

et al. 2001

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We investigate the atomic structure of the fivefold surface of an icosahedral AlCu-Fe alloy, using scanning tunneling microscopy (STM) imaging and a special dynamical low energy-electron diffraction (LEED) method. STM indicates that the step heights adopt (primarily) two values in the ratio of tau, but the spatial distribution of these two values does not follow a Fibonacci sequence, thus breaking the ideal bulk-like quasicrystalline layer stacking order perpendicular to the surface. The appearance of screw dislocations in the STM images is another indication of imperfect quasicrystallinity. On the other hand, the LEED analysis, which was successfully applied to Al-Pd-Mn in a previous study, is equally successful for Al-Cu-Fe. Similar structural features are found for both materials, in particular for interlayer relaxations and surface terminations. Although there is no structural periodicity, there are clear atomic planes in the bulk of the quasicrystal, some of which can be grouped in recurring patterns. The surface tends to form between these grouped layers in both alloys. For Al-Cu-Fe, the step heights measured by STM are consistent with the thicknesses of the grouped layers favored in LEED. These results suggest that the fivefold Al-Cu-Fe surface exhibits a quasicrystalline layering structure, but with stacking defects.

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Section: Introductionmentioning

confidence: 99%

Structural aspects of the fivefold quasicrystalline Al–Cu–Fe surface from STM and dynamical LEED studies

et al. 2001

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“…These observations have been confirmed. 19 Using the DoniachSunjic XPS line shape to fit the experimental data, CJJ found that the narrowing of the Mn 2p 3/2 line is due to a decrease of both the asymmetry parameter and the core-level width, indicative of a combination of electronic effects near the Fermi edge. The narrowing of the Mn 2p 3/2 line was postulated to be the fingerprint of a well ordered quasicrystalline surface.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure of quasicrystalline surfaces: Effects of surface preparation and bulk structure

et al. 2000

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We elucidate the nature of the surface electronic properties of quasicrystalline Al-Pd-Mn. We do this by using photoelectron and Auger electron spectroscopies, and by making a variety of comparisons-across types of bulk samples, and across methods of surface preparation. The main conclusions are these: (i) The narrow Mn 2p 3/2 core-level line observed in the icosahedral phase is a fingerprint of a suppression in the density of states (a pseudogap) at the Fermi level and is not unique to the quasicrystalline phase. It is also independent of the symmetry of the quasicrystalline surface. The Auger line shape is also affected and may be used as a fingerprint of a pseudogap. (ii) A similarly narrow Fe 2p 3/2 core-level line characterizes the icosahedral Al-Cu-Fe quasicrystal, consistent with the expectation that the electronic structure is of general importance in the stabilization of icosahedral phases. (iii) In icosahedral Al-Pd-Mn, the pseudogap of the bulk is not retained up to the surface immediately after fracture, but can be restored by annealing, or by sputter annealing to sufficiently high temperatures. Assuming that the pseudogap reflects an electronic stabilization of the atomic structure, these results suggest that the heat-treated surfaces are more stable than the surface obtained by fracturing at room temperature. We elucidate the nature of the surface electronic properties of quasicrystalline Al-Pd-Mn. We do this by using photoelectron and Auger electron spectroscopies, and by making a variety of comparisons-across types of bulk samples, and across methods of surface preparation. The main conclusions are these: ͑i͒ The narrow Mn 2p 3/2 core-level line observed in the icosahedral phase is a fingerprint of a suppression in the density of states ͑a pseudogap͒ at the Fermi level and is not unique to the quasicrystalline phase. It is also independent of the symmetry of the quasicrystalline surface. The Auger line shape is also affected and may be used as a fingerprint of a pseudogap. ͑ii͒ A similarly narrow Fe 2p 3/2 core-level line characterizes the icosahedral Al-Cu-Fe quasicrystal, consistent with the expectation that the electronic structure is of general importance in the stabilization of icosahedral phases. ͑iii͒ In icosahedral Al-Pd-Mn, the pseudogap of the bulk is not retained up to the surface immediately after fracture, but can be restored by annealing, or by sputter annealing to sufficiently high temperatures. Assuming that the pseudogap reflects an electronic stabilization of the atomic structure, these results suggest that the heat-treated surfaces are more stable than the surface obtained by fracturing at room temperature.

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“…As remarked in the introduction, it has already been demonstrated that x-ray standing waves are established in quasicrystals, associated with known diffraction conditions, and that measurements of the absorption in these standing waves by atoms in the bulk, both in total and in an element-specific fashion, do yield profiles that can be fitted using non-zero CF values [33][34][35][36]. It has been shown that, even in a Fibonacci sequence of interlayer spacings, the atoms are not randomly located relative to the periodic diffraction planes, but are clustered in such a way as to be consistent with this observation [32].…”

Section: Discussionmentioning

confidence: 99%

“…On a quasicrystal surface, however, there is no such lateral periodicity, and this simplicity is lost. However, the same problem of a lack of true periodicity underlies any diffraction or standing wave creation in a quasicrystal, and it is well established that meaningful information can be extracted on the bulk structure of quasicrystals from these methods [32,[34][35][36]. We describe here how similar information may be extracted from NIXSW studies of the quasicrystal surface.…”

Section: Nixsw From the Quasi-periodic Planes Inclined To The Surfacementioning

confidence: 99%

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X-ray standing wave study of Si clusters on a decagonal Al-Co-Ni quasicrystal surface

et al. 2015

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Quantitative adsorption structure determinations on quasicrystals are scarce because most techniques for measuring surface structures are not well suited to the complex and infinite unit cells of quasicrystals. The normal incidence standing x-ray wave field technique presents a solution to these problems because it can be made inherently surface sensitive and does not involve extensive computational effort. We describe a method for applying this technique to adsorbates on quasicrystals, with specific application to a submonolayer of Si atoms on a decagonal Al-Co-Ni surface. We demonstrate the sensitivity of the technique to both adsorption site and geometry, leading to the conclusion that the Si atoms, which form 6-atom pentagonal clusters, have an average height of 1.77 ± 0.05 Å above pentagonal hollow sites, with a significant height variation among the Si atoms in the cluster. In particular, the central Si atom sits more deeply than the five surrounding Si atoms, which are, on average, 2.7 Å away from the central Si atom. Although this study was performed on a decagonal quasicrystal that is periodic perpendicular to the surface, we describe how the technique can be applied to cases where that is not true.

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Characterization And Properties Of The AIPdMn 5 Surface

Abstract: The surface of the AlPdMn quasicrystal perpendicular to a fivefold axis has been probed by LEED, XPS, Auger spectroscopy and surface EXAFS.

Cited by 10 publications

References 9 publications

Structural aspects of the fivefold quasicrystalline Al–Cu–Fe surface from STM and dynamical LEED studies

Structural aspects of the fivefold quasicrystalline Al–Cu–Fe surface from STM and dynamical LEED studies

Electronic structure of quasicrystalline surfaces: Effects of surface preparation and bulk structure

X-ray standing wave study of Si clusters on a decagonal Al-Co-Ni quasicrystal surface

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