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© 2011 American Physical Society. We acknowledge J. Osterwalder and T. Greber for their continuous support and also the help of the beamline staffs from both the SRC and SLS synchrotrons during experiments. This work was supported by the Spanish Ministerio de Ciencia e Innovación (Grants No. FIS2010-19609-C02-02, FIS2008- 00399, MAT2010-21156-C03-01, and MAT2010-21156-C03-02 and through the Research Program Ramon y Cajal) and the Basque Government (IT-257-07). The SRC is funded by the National Science Foundation (Award No. DMR-0084402)., The photoemission cross-section of Shockley states of Cu(111) and Ag(111) surfaces is studied over a wide range of photon energies. The constant initial-state spectra are very different for the two surfaces and show rich structure that does not follow the generally accepted nearly free electron model for the final state. Angle resolved photoemission data are interpreted within a one-step ab initio theory, revealing a multiple Bloch wave structure of photoemission final states. The inelastic scattering parameter-optical potential-is determined, and the energy dependence of the mean free path of the outgoing electron is calculated, which turns out to be the key for the understanding of the photoemission cross-section curve. These are essential steps for future exploration of wave function perturbations in the presence of surface nanostructures., Spanish Ministerio de Ciencia e Innovacion, Basque Government, National Science Foundation, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

The clean surface of Au(100) presents a complex reconstruction characterized by a hexagonal topmost layer. We report an angle-resolved photoemission study of the electronic structure of this surface, including an analysis of the Fermi surface, combined with structural information from low-energy electron diffraction and scanning tunneling microscopy. In the complex Fermi surface map found, we identify different contributions from the bulk bands, from interface states located below the hexagonal topmost layer, and from the hexagonal topmost layer itself. The electronic states related to this layer exhibit quasi-one-dimensional character, in agreement with the chain aspect of the reconstructed layer, as demonstrated by their dispersion, periodicity, and reciprocal space location. © 2012 American Physical Society.

The photoemission cross-section of Shockley states of Cu(111) and Ag(111) surfaces is studied over a wide range of photon energies. The constant initial-state spectra are very different for the two surfaces and show rich structure that does not follow the generally accepted nearly free electron model for the final state. Angle resolved photoemission data are interpreted within a one-step ab initio theory, revealing a multiple Bloch wave structure of photoemission final states. The inelastic scattering parameter-optical potential-is determined, and the energy dependence of the mean free path of the outgoing electron is calculated, which turns out to be the key for the understanding of the photoemission cross-section curve. These are essential steps for future exploration of wave function perturbations in the presence of surface nanostructures. 2011 American Physical Society.

In angle-resolved photoemission (ARPES) from crystalline solids, wave-vector conservation applies to the two-dimensional (2D) surface, which may thus be defined as the reference plane in ARPES. We investigate whether such reference varies for photoemitted electrons in nanometer-sized systems that expose different crystal planes. To this aim, we exploit the structural tunability of the Ag/Cu(223) system which is capable of offering surfaces with periodic arrays of nanofacets of varying size and orientation. A thorough, photonenergy- dependent analysis of the surface states confined to such nanostructures is performed comparing different reference planes for photoemitted electrons. Assuming the premise that k|| must be a good quantum number for 2D states, we conclude that the (final state) photoelectron reference direction is not the average optical direction but the local facet that confines the (initial state) surface electrons. Moreover, in the general case of nanostructured systems with uneven surfaces, we show how the photoelectron reference plane can be empirically determined through such a photon-energy-dependent ARPES analysis. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Stepped Cu nanostripes with varying terrace widths are self-assembled during Ag-induced periodic faceting of vicinal Cu(111). By changing Ag coverage the average terrace size within individual Cu stripes is readily tuned, making it possible to select the one-dimensional or two-dimensional character of surface states. Furthermore, the average terrace size can be smoothly switched from 10 to 30 Å, thereby tracking the transition from step-lattice, quasi-two-dimensional umklapp bands to terrace-confined one-dimensional quantum well states.

Electron bands in solids can be determined in angle-resolved photoemission experiments from thin films, where the perpendicular wave vector (k⊥) uncertainty that characterizes photoemission from bulk crystals is removed. However, the comparison with state-of-the-art quasiparticle band-structure calculations has never been done. In this work we have mapped both initial-state (occupied) and final-state (empty) E(k⊥) bands along the A axis of aluminum, from photon-energy- and thickness-dependent quantum-well spectra of aluminum films. For final states the best fit is obtained with inverse low-energy electron diffraction band structure calculations. For initial-state bands of Cu and Al, thin-film data display excellent agreement with bulk quasiparticle theory, suggesting the use of thin films as model systems to investigate fine effects in the crystal band structure.

We report an investigation of the electronic band structure of the SixSn(1−x)/Si(111)−(√3×√3)R30° solid solution using angle-resolved photoemission. This reconstruction was studied in the coverage range between 0.15 and 0.40 monolayers at room and low temperature, with special emphasis on the analysis of the symmetry and morphology of the surface states and the metallic character as a function of temperature and coverage. While there is no indication of a (3×3) pattern at low temperature with structural techniques, strikingly clear features of this phase are found in the valence band analysis for a coverage of 0.33 ML. We present also an analysis of the influence of the Si intermixing in the surface-state behavior and metallic character.

The Cu(111) surface state has been mapped for vicinal surfaces with variable step densities by angle-resolved photoemission. Using tunable synchrotron radiation to vary the k dependence perpendicular to the surface, as well as the k∥ dependence, we find a switch between two qualitatively different regimes at a miscut of 7° (17 Å terrace width). For larger miscut angles the step modulation of the wave function dominates, and for smaller miscut angles the terrace modulation dominates. These observations resolve an apparent inconsistency between prior photoemission and STM results.

The electronic structure of ultrathin Cu films deposited on top of an FCC-Co(1 0 0) film has been studied by angle- and spin-resolved photoemission. Deposition at liquid-nitrogen temperature allows the formation of sharp interfaces that produces well-defined quantum-well states in the Cu valence band. Furthermore, short-wavelength quantum-well states originating from the neck of the Cu Fermi surface are only visible after low-temperature deposition. Spin-resolved spectra show that these states, which are predicted to dominate oscillatory magnetic coupling in multilayers, exhibit minority spin character.