Formation of a stable deacagonal quasicrystalline Al-Pd-Mn surface layer

We report the in situ formation of an ordered equilibrium decagonal Al-Pd-Mn quasicrystal overlayer on the 5-fold symmetric surface of an icosahedral Al-Pd-Mn monograin. The decagonal structure of the epilayer is evidenced by x-ray photoelectron diffraction, low-energy electron diffraction and electron backscatter diffraction. This overlayer is also characterized by a reduced density of states near the Fermi edge as expected for quasicrystals. This is the first time that a millimeter-size surface of the stable decagonal Al-Pd-Mn is obtained, studied and compared to its icosahedral counterpart.Comment: Submitted to Phys. Ref. Lett. (18 July 2001

Electronic Structure of the YH3 Phase from Angle-Resolved Photoemission Spectroscopy

Yttrium can be loaded with hydrogen up to high concentrations causing dramatic structural and electronic changes of the host lattice. We report on angle-resolved photoemission experiments of the Y trihydride phase. Most importantly, we find the absence of metal d-bands at the Fermi level and a set of flat, H-induced bands located at much higher binding energy than predicted, indicating an increased electron affinity at H sites

Quasicrystalline nature of quasicrystal surfaces: A photoemission study

Differently prepared surfaces of quasicrystalline i-Al-Pd-Mn are analyzed using angle-resolved photoemission in the x-ray andultraviolet range of photon energies. Depending on the preparation, we find both surfaces with crystalline structure and metallic character, and surfaces with quasicrystalline structural fingerprints and a suppressed density of states at the Fermi level, compatible with a pseudogap

Energetic and spatial bonding properties from angular distributions of ultraviolet photoelectrons: application to the GaAs(110) surface

Angle-resolved ultraviolet photoemission spectra are interpreted by combining the energetics and spatial properties of the contributing states. One-step calculations are in excellent agreement with new azimuthal experimental data for GaAs(110). Strong variations caused by the dispersion of the surface bands permit an accurate mapping of the electronic structure. The delocalization of the valence states is discussed analogous to photoelectron diffraction. The spatial origin of the electrons is determined, and found to be strongly energy dependent, with uv excitation probing the bonding region.Comment: 5 pages, 3 figures, submitted for publicatio

Ag on Cu(001) and other noble-metal films studied by full-hemispherical photoelectron diffraction

An 8 monolayer Ag film has been deposited in situ on Cu(001) at room temperature. Its structure has been investigated by X-ray photoelectron diffraction, presented as full solid-angle intensity maps, and by low-energy electron diffraction. The formation of a compact Ag(111)-like overlayer with one preferential domain has been observed. Annealing the Ag film at about 300°C creates Ag islands on the Cu(001) substrate. The system is put into the context of eight other noble-metal (Ag, Au and Pt) films deposited on different substrates (Cu, Pt, Cu3Au, Bi2Sr2CaCu2O8+x). The crystalline orientation of the overlayers with respect to the substrate and the formation of a surface alloy are discussed