Structure and oxidation at quasicrystal surfaces

Thiel, Patricia A.

doi:10.1016/j.progsurf.2004.05.005

Cited by 10 publications

(5 citation statements)

References 57 publications

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“…This is illustrated by the change in peak position for Al, but not for Zn and Pd, in comparing Figures 7b and c; (3) the oxide of aluminum covers the other two metals. This is consistent with studies of other Al-rich quasicrystals such as Al-Cr-Fe, Al-Cu-Fe, Al-Pd-Mn, and Al-Cu-Fe-Cr, which all show that Al is the only metal that oxidizes in vacuum and forms a passivating layer of pure or nearly-pure alumina on top of the other metals, accompanied by surface segregation of Al [22,23].…”

Section: Philosophical Magazine 2883supporting

confidence: 90%

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Weak bonding of Zn in an Al-based approximant based on surface measurements

Yuen

Ünal

Jing

et al. 2010

Philosophical Magazine

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We have studied two surfaces of a new Al-Pd-Zn approximant using mass spectrometry, X-ray photoemission spectroscopy (XPS) and scanning tunneling microscopy (STM). Zn is bonded weakly in this approximant, perhaps as weakly as in elemental Zn. This is based upon three observations: (1) the low vapor pressure of Zn above the approximant (detectable in the gas phase at 600 K), (2) preferential sputtering of Zn (contrary to the usual preferential sputtering of Al in Al-rich quasicrystals), and (3) preferential surface segregation of Zn. We further show that preferential segregation -and perhaps incipient evaporation -causes the surface to roughen, preventing it from forming a terrace-step morphology. Finally, our data show that at low O2 pressures, Al oxidizes. In air, Zn oxidizes as well. All results and conclusions are similar for the two-fold and pseudo-10-fold surfaces. RightsThis article is (co-)authored by an employee of the United States Government and is not subject to copyright in the United States (17 U.S.C. §105). Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden.The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. We have studied two surfaces of a new Al-Pd-Zn approximant using mass spectrometry, X-ray photoemission spectroscopy (XPS) and scanning tunneling microscopy (STM). Zn is bonded weakly in this approximant, perhaps as weakly as in elemental Zn. This is based upon three observations: (1) the low vapor pressure of Zn above the approximant (detectable in the gas phase at 600 K), (2) preferential sputtering of Zn (contrary to the usual preferential sputtering of Al in Al-rich quasicrystals), and (3) preferential surface segregation of Zn. We further show that preferential segregation -and perhaps incipient evaporation -causes the surface to roughen, preventing it from forming a terrace-step morphology. Finally, our data show that at low O 2 pressures, Al oxidizes. In air, Zn oxidizes as well. All results and conclusions are similar for the two-fold and pseudo-10-fold surfaces. Philosophical MagazineVol. 91, Nos. 19-21, 1-21 July 2011, 2879-

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Section: Philosophical Magazine 2883supporting

confidence: 90%

“…Following a well-established approach [22], we use XPS peak intensities to determine qualitative changes in surface metal concentration, and peak positions to determine which element is engaged in chemical bonding. Peak positions are illustrated by the XPS data in Figure 7.…”

Section: Philosophical Magazine 2883mentioning

confidence: 99%

Weak bonding of Zn in an Al-based approximant based on surface measurements

Yuen

Ünal

Jing

et al. 2010

Philosophical Magazine

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“…Formation of an oxide layer on top of the quasicrystalline surface often leads to Al surface segregation and Al depletion below the surface. As the region of phase stability for quasicrystals is often narrow, such a depletion of aluminium in the bulk can lead to phase conversion when thin films or small particles are used at elevated temperatures [90,91]. A similar effect can also be observed when crystal growth is performed in the presence of small traces of oxygen (or water vapor) contamination.…”

Section: Solid Phase Transformationsmentioning

confidence: 99%

Those Properties of CMAs We Know Something About

Fournée

Barthés-Labrousse

Dubois

2008

SSP

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New tools are nowadays available to solve the crystallographic structure of complex compounds in metallic alloy systems and a vivid interest manifests itself to discover new compounds in multi-constituent alloys with hundreds or more atoms per unit cell. Meanwhile, it is observed that the metallic character of the alloy progressively disappears with increasing the number of atoms in the unit cell. This contribution focuses at a few examples of this atypical behavior of complex metallic alloys, including quasicrystals as the ultimate state of structural complexity in a crystal made of metals. Emphasis is put on surface properties.

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“…[2][3][4][5][6][7][8][9] Many studies have addressed the central question of whether the bulk, aperiodic structure continues unperturbed to the surface. That is, whether the surface is bulk truncated, as if made by cleaving a fixed, bulk slab.…”

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confidence: 99%