Quasiperiodic layers of free-electron metals studied using electron diffraction

Abstract

Using electron diffraction, we show that free-electron metals, such as sodium and potassium, form a highly regular quasiperiodic monolayer on the fivefold surface of icosahedral Al-Pd-Mn and that the quasiperiodicity propagates up to the second layer in sodium. Our photoelectron spectroscopy results show that the quasicrystalline alkali-metal adlayer does not exhibit a pseudogap near the Fermi level thought to be characteristic for the electronic structure of quasicrystalline materials. Calculations based on density functional theory provide a model structure for the quasicrystalline alkali-metal monolayer and confirm the absence of a pseudogap. Disciplines Metallurgy CommentsThis article is from Physical Review B 79 (2009) Using electron diffraction, we show that free-electron metals, such as sodium and potassium, form a highly regular quasiperiodic monolayer on the fivefold surface of icosahedral Al-Pd-Mn and that the quasiperiodicity propagates up to the second layer in sodium. Our photoelectron spectroscopy results show that the quasicrystalline alkali-metal adlayer does not exhibit a pseudogap near the Fermi level thought to be characteristic for the electronic structure of quasicrystalline materials. Calculations based on density functional theory provide a model structure for the quasicrystalline alkali-metal monolayer and confirm the absence of a pseudogap.

Quasiperiodic Pb monolayer on the fivefoldi-Al-Pd-Mnsurface: Structure and electronic properties

“…This is in contrast to the multilayer growth observed for alkali 15 or Bi ͑Ref. 13͒ films on the fivefold i-Al-Pd-Mn surface.…”

“…On the other hand, we predicted that highly regular quasiperiodic monolayers can be formed by Na and K atoms on the fivefold surface of i-Al-Pd-Mn surface, 18 and this was later confirmed experimentally. 15 Structurally stable quasiperiodic monolayers can be formed on quasiperiodic substrates only. Unsupported quasiperiodic monolayers are unstable.…”

“…During recent years many attempts have been made to produce quasiperiodic single-element overlayers on quasicrystalline substrates. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] It is known that in the bulk quasicrystalline ordering is realized only in multicomponent alloys and therefore the possibility to produce quasiperiodic single-element overlayers is of fundamental importance. However, to grow a thin film with quasiperiodic long-range order turned out to be rather difficult.…”

Bulk Electronic Structure of Quasicrystals

“…While cleaving retains the bulk composition at the surface, ion sputtering makes the surface Pd rich. Therefore, to restore the surface composition and quasicrystallinity, the sputtered specimens were annealed for 1.5 hours at 900-1000 K [12,13]. The measurements were performed at the P09 beam line [14] at Petra III, Deutsches Elektronen-Synchrotron, Hamburg and at ID32 beam line [15] at the European Synchrotron Radiation Facility, Grenoble using 7.93 and 5.95 keV x rays at 300 K and 40 K. Post-monochromators were used to improve the energy resolution and stability.…”

An ultrahigh vacuum compatible sample holder for studying complex metal surfaces

“…1,2 In both these systems, an atomically clean surface may be obtained by rare gas ion sputtering and subsequent annealing to high temperatures to regain the surface composition similar to the bulk that is offset by preferential sputtering cross-section of the different elements. Examples of such complex metallic alloys are quasicrystals and ferromagnetic shape memory alloys ͑FSMAs͒.…”