Formation of a Stable Decagonal Quasicrystalline Al-Pd-Mn Surface Layer

Naumović, D.; Aebi, Philipp; Schlapbach, L.; Beeli, C.; Kunze, Karsten; Lograsso, Thomas A.; Delaney, D.W.

doi:10.1103/physrevlett.87.195506

Cited by 37 publications

(24 citation statements)

References 36 publications

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“…5͑a͒ and 5͑b͒ are also similar to those observed on the decagonal quasicrystal overlayer grown on the fivefold surface of the i-Al-Pd-Mn sample. 28 As XPD probes the local real-space environment around the selected emitting atoms, these measurements reveal an average short-range decagonal ordering around the Al and Co atoms at the near surface. From the cluster arrangements described in Sec.…”

Section: Fig 5 ͑Color Online͒ Experimental Xpd Patterns Of ͑A͒ Al 2smentioning

confidence: 98%

Structure investigation of the (100) surface of the orthorhombicAl13Co4crystal

et al. 2009

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We present a detailed study of the ͑100͒ surface of the orthorhombic Al 13 Co 4 crystal using both experimental and ab initio computational methods. This complex metallic alloy is an approximant of the decagonal Al-Ni-Co quasicrystalline phase. After sputter-annealing preparation of the surface at 1073 K, the low-energy electron diffraction pattern recorded exhibits a pseudotenfold symmetry with lattice parameters consistent with those of the bulk model. At this stage, scanning tunneling microscopy ͑STM͒ measurements reveal two different types of surface terminations. A comparison between these two surface structures and the bulk planes indicate that the terminations correspond either to an incomplete puckered layer ͑P͒ or to an incomplete flat layer ͑F͒. At 1173 K, the majority of the surface consists of P layer terminations. STM images calculated from our proposed surface model are in good agreement with experimental images. X-ray photoelectron diffraction patterns and single scattering cluster calculations further confirm that the local atomic arrangements present in the bulk model are preserved within the near-surface region.

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Section: Fig 5 ͑Color Online͒ Experimental Xpd Patterns Of ͑A͒ Al 2smentioning

confidence: 98%

Structure investigation of the (100) surface of the orthorhombicAl13Co4crystal

et al. 2009

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“…10 At higher temperatures, the surface usually changes to a flat quasicrystalline phase. 24 An intermediate phase that is both quasicrystalline and rough may form around 700 K. 8 Flat crystalline phases can also form above 700 K. [25][26][27][28][29] The factors that select between crystalline and quasicrystalline surface phases above 700 K are poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Terrace selection during equilibration at an icosahedral quasicrystal surface

et al. 2005

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We investigate the equilibration of a fivefold surface of the icosahedral Al-Pd-Mn quasicrystal at 900-915 and 925-950 K, using scanning tunneling microscopy. After annealing at the lower temperatures, there is a high density of shallow voids on some terraces but not on others; at 925-950 K, the void-rich terraces are much rarer. The terminations that are consumed by voids exhibit a distinctive local atomic configuration, called a "ring" by previous authors. Apparently, through growth and coalescence of the voids, a different termination becomes exposed on the host terraces, which also leads to a change in step heights at the edges of the terraces. We suggest that the shallow steps associated with the voids, and the ring configuration, signal a surface that is in an intermediate stage of structural equilibration. We investigate the equilibration of a fivefold surface of the icosahedral Al-Pd-Mn quasicrystal at 900-915 and 925-950 K, using scanning tunneling microscopy. After annealing at the lower temperatures, there is a high density of shallow voids on some terraces but not on others; at 925-950 K, the void-rich terraces are much rarer. The terminations that are consumed by voids exhibit a distinctive local atomic configuration, called a "ring" by previous authors. Apparently, through growth and coalescence of the voids, a different termination becomes exposed on the host terraces, which also leads to a change in step heights at the edges of the terraces. We suggest that the shallow steps associated with the voids, and the ring configuration, signal a surface that is in an intermediate stage of structural equilibration.

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“…The equilibrium with the bulk is mediated by diffusion of all components of the alloy. At the typical annealing temperatures in the range of 820 to 920 K [1][2][3][4][5][6][7]13,14] this is assured. For the equilibrium with the vapor, we have to consider the vapor pressures of the components, of which Mn has the highest one.…”

Section: -2mentioning

confidence: 99%

“…Therefore, surfaces of quasicrystals, i.e., solids with a well defined but nonperiodic crystallography, were intensively investigated in the last decade. However, against all expectations, not only one surface structure but rather a large number of different surface structures were observed, e.g., on icosahedral AlPd-Mn quasicrystals [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. These different surface structures differ even in their basic symmetry, which ranges from cubic via orthorhombic and decagonal to icosahedral.…”

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confidence: 96%

Nonicosahedral Equilibrium Overlayers of Icosahedral Quasicrystals

2005

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We demonstrate that icosahedral Al-Pd-Mn quasicrystals can have nonicosahedrally ordered thermodynamic equilibrium overlayers. The formation of orthorhombic or decagonal equilibrium surface structures is determined by the phase equilibrium of the ternary alloy at given composition and temperature as well as by the surface acting as nucleation site. Nonequilibrium steady-state orthorhombic and hexagonal structures can also be derived with the same methodology when taking preferential evaporation into account. The results describe consistently all presently observed surface structures. DOI: 10.1103/PhysRevLett.95.256105 PACS numbers: 68.35.ÿp, 61.44.Br, 64.75.+g One of the scientifically most intriguing questions in the field of nonperiodic solids is the thermodynamic stability of their surfaces. The stability of the surfaces is closely connected to the formation mechanism and a major factor in the growth of nonperiodic solids. Therefore, surfaces of quasicrystals, i.e., solids with a well defined but nonperiodic crystallography, were intensively investigated in the last decade. However, against all expectations, not only one surface structure but rather a large number of different surface structures were observed, e.g., on icosahedral AlPd-Mn quasicrystals [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. These different surface structures differ even in their basic symmetry, which ranges from cubic via orthorhombic and decagonal to icosahedral. To date it is unclear if these surface structures are equilibrium surfaces or not. In fact, for all observed nonicosahedral structures it is typically assumed that they were obtained kinetically due to preferential sputtering, preferential desorption, and/or segregation during the cleaning procedures [5,7,9,12]. In contrast, the icosahedrally ordered surface structure is implicitly considered to be the equilibrium surface of an icosahedral quasicrystal, although no experimental proof has ever been published. So far only the facets of grown-in voids were identified as equilibrium surfaces, but except their composition, nothing is known about the atomic structure [11,15]. As a consequence, at present the structure of the equilibrium surface(s) of icosahedral quasicrystals is not known.In this Letter we determine the thermodynamically stable structures at surfaces of icosahedral Al-Pd-Mn quasicrystals, using extended annealing experiments and a precision determination of the relevant parts of the ternary Al-Pd-Mn phase diagram. On this basis we distinguish between equilibrium and kinetically reached steady-state surface structures and extract their formation mechanisms. We show that in all cases the driving force for the formation of crystallographically different overlayers is the motion of the system toward its phase equilibrium, modulated by preferential evaporation, if present. These results allow us to demonstrate that both nonicosahedral (orthorhombic and decagonal) and icosahedral structures can exist in thermodynamic equilibrium at the surfaces, depending on the i...

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Formation of a Stable Decagonal Quasicrystalline Al-Pd-Mn Surface Layer

Cited by 37 publications

References 36 publications

Structure investigation of the (100) surface of the orthorhombicAl13Co4crystal

Structure investigation of the (100) surface of the orthorhombicAl13Co4crystal

Terrace selection during equilibration at an icosahedral quasicrystal surface

Nonicosahedral Equilibrium Overlayers of Icosahedral Quasicrystals

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