Study of the response of the fivefold i-AlPdMn surface to different temperature treatments

Schmithüsen, Frank; Cappello, Giovanni; Boissieu, M. de; Boudard, Michel; Comin, F.; Chevrier, J.

doi:10.1016/s0039-6028(99)00984-x

Cited by 41 publications

(38 citation statements)

References 26 publications

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“…Schmithüsen et al 26 reported that evaporation of Mn begins at 900 K and of Al at 1000 K, this order corresponding to the order of the elemental vapor pressures. Hence, evaporation at these temperatures is nonstoichiometric.…”

Section: Discussionmentioning

confidence: 99%

“…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%

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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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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Terrace selection during equilibration at an icosahedral quasicrystal surface

et al. 2005

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“…Recent evaporation experiments showed, however, that no evaporation is detectable up to about 600°C from surfaces of AlPd-Mn quasicrystals. 23 Starting at temperatures of about 627°C the first traces of Mn appear and above about 727°C Al evaporation occurs. Thus at lower temperatures, in particular, at temperatures as low as 350°C, evaporation is negligible.…”

Section: Discussionmentioning

confidence: 99%

“…[20][21][22] To date the physical origins of these effects have been attributed to preferential sputtering, preferential evaporation under Langmuir conditions, chemical inhomogeneities, and segregation. However, it has recently been shown that evaporation starts only above 900 K, 23 i.e., a temperature much higher than that needed for the abovementioned changes of the surface structure and composition. Furthermore, the preferential sputtering does not occur on cleaved surfaces.…”

Section: Introductionmentioning

confidence: 99%

Surface structure of Al-Pd-Mn quasicrystals: Existence of supersaturated bulk vacancy concentrations

et al. 2003

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We identified the presence and chemical nature of bulk vacancies in Al-Pd-Mn quasicrystals by measuring the structure and composition of two-and fivefold cleavage surfaces of different preannealed quasicrystals subjected to postcleavage heat treatments using scanning electron microscopy and Auger electron spectroscopy. A strong dependence of the surface structure from the preannealing is observed and explained by varying concentrations of bulk vacancies. The analysis of the data shows that as-grown Al-Pd-Mn quasicrystals contain Al, Pd, and Mn vacancies in supersaturated but near stoichiometric concentrations, while long-term preannealed samples contain a much lower vacancy concentration, with a tendency to have excess Al vacancies. We found that Al and Mn vacancies are more mobile at lower temperatures than Pd vacancies, and that the diffusion of Mn vacancies is directly coupled to the mobility of Al vacancies. The results demonstrate that the evolution of the surface structure is primarily affected by bulk vacancies migrating toward the surface during heat treatments and provide a new methodology to characterize the vacancies in intermetallic alloys. We identified the presence and chemical nature of bulk vacancies in Al-Pd-Mn quasicrystals by measuring the structure and composition of two-and fivefold cleavage surfaces of different preannealed quasicrystals subjected to postcleavage heat treatments using scanning electron microscopy and Auger electron spectroscopy. A strong dependence of the surface structure from the preannealing is observed and explained by varying concentrations of bulk vacancies. The analysis of the data shows that as-grown Al-Pd-Mn quasicrystals contain Al, Pd, and Mn vacancies in supersaturated but near stoichiometric concentrations, while long-term preannealed samples contain a much lower vacancy concentration, with a tendency to have excess Al vacancies. We found that Al and Mn vacancies are more mobile at lower temperatures than Pd vacancies, and that the diffusion of Mn vacancies is directly coupled to the mobility of Al vacancies. The results demonstrate that the evolution of the surface structure is primarily affected by bulk vacancies migrating toward the surface during heat treatments and provide a new methodology to characterize the vacancies in intermetallic alloys. Keywords Ames Laboratory Disciplines Physical Chemistry Comments This article is from

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“…Choosing an appropriate annealing temperature is crucial in producing a quasicrystalline surface. 68,69 Annealing was done at 773 K which yielded a clear fivefold low-energy electron diffraction pattern. 68,69 The surface cleanliness was verified using Auger electron spectroscopy.…”

Section: Methodsmentioning

confidence: 99%

Absence of fine structure in the photoemission spectrum of the icosahedral Al-Pd-Mn quasicrystal

et al. 2001

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Absence of fine structure in the photoemission spectrum of the icosahedral Al-Pd-Mn quasicrystal AbstractThe results of the low-temperature ultrahigh-energy-resolution photoemission studies of a single-grain icosahedral alloy Al 70 Pd 21.5 Mn 8.5 have been presented. The existence of the theoretically predicted pseudogap in the density of states at the Fermi energy has been confirmed. No evidence of the theoretically predicted spikiness of the density of states could be observed. It has been suggested that the failure to detect the predicted spikiness of the density of states in icosahedral quasicrystals is consistent with the results of Zijlstra and Janssen [Europhys. Lett. 52, 578 (2000)] who showed that the spikiness occurs only in lowerorder periodic approximants to icosahedral quasicrystals, but does not survive in the quasiperiodic limit. Disciplines Condensed Matter Physics | Metallurgy CommentsThis article is from Physical Review B 64 (2001) The results of the low-temperature ultrahigh-energy-resolution photoemission studies of a single-grain icosahedral alloy Al 70 Pd 21.5 Mn 8.5 have been presented. The existence of the theoretically predicted pseudogap in the density of states at the Fermi energy has been confirmed. No evidence of the theoretically predicted spikiness of the density of states could be observed. It has been suggested that the failure to detect the predicted spikiness of the density of states in icosahedral quasicrystals is consistent with the results of Zijlstra and Janssen ͓Europhys. Lett. 52, 578 ͑2000͔͒ who showed that the spikiness occurs only in lower-order periodic approximants to icosahedral quasicrystals, but does not survive in the quasiperiodic limit.

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Study of the response of the fivefold i-AlPdMn surface to different temperature treatments

Cited by 41 publications

References 26 publications

Terrace selection during equilibration at an icosahedral quasicrystal surface

Terrace selection during equilibration at an icosahedral quasicrystal surface

Surface structure of Al-Pd-Mn quasicrystals: Existence of supersaturated bulk vacancy concentrations

Absence of fine structure in the photoemission spectrum of the icosahedral Al-Pd-Mn quasicrystal

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