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Université de Neuchâtel

Use of angle-resolved photoemission and density functional theory for surface structural analysis of YSi2

Koitzsch, Christian ; Bovet, M. ; Garnier, Michael Bernard Gunnar ; Aebi, Philipp ; Rogero, C. ; Martín-Gago, J. A.

In: Surface Science, 2004, vol. 566-568, no. 2, p. 1047-1051

The atomic structure of two-dimensional yttrium silicide epitaxially grown on Si(1 1 1) was investigated by means of density functional theory calculations and angle-resolved photoemission experiments. The obtained accuracy of the calculations allowed to discriminate different surface arrangements in a quantitative way via comparing their theoretical band structure to the experimental result....

Université de Neuchâtel

On the search for Fermi surface nesting in quasi-2D materials

Aebi, Philipp ; Pillo, Th. ; Berger, Helmuth ; Lévy, F.

In: Journal of Electron Spectroscopy and Related Phenomena, 2001, vol. 117-118, p. 433-449

We investigate a number of isostructural, quasi-two dimensional transition metal dichalcogenides with respect to Fermi surface nesting. Using angle-resolved photoemission we find no clear evidence for Fermi surface nesting as a key scenario for charge density wave formation in these materials. However, interesting and unusual behavior has been discovered. For 1T-TaS2 in the...

Université de Neuchâtel

A monochromatized multiple energy laboratory UV source for k-space imaging

Pillo, Th. ; Patthey, L. ; Boschung, E. ; Hayoz, J. ; Aebi, Philipp ; Schlapbach, Louis

In: Journal of Electron Spectroscopy and Related Phenomena, 1998, vol. 97, no. 3, p. 243-252

A laboratory set-up for ultraviolet (UV) photoelectron spectroscopy combining a high intensity UV source and a toroidal UV monochromator, both being commercially available, is described. The source is modified in order to maximize the solid angle collected by the monochromator. Scanning its exit arm length allows for the optimization of the photon intensity as well as the energy resolution by...

Université de Neuchâtel

Charge density waves in 1T-TaS2: an angle-resolved photoemission study

Clerc, Florian ; Bovet, M. ; Berger, Helmuth ; Despont, Laurent ; Koitzsch, Christian ; Garnier, Michael Bernard Gunnar ; Aebi, Philipp

In: Surface Science, 2006, vol. 351, no. 3-4, p. 245-249

The transition metal dichalcogenide 1T-TaS2 is a layered material exhibiting charge density waves. Based on angle-resolved photoemission experiments mapping spectral weight at the Fermi surface and density functional theory calculations we discuss possible mechanisms involved with the creation of charge density waves. At first the flat parts of the elliptically shaped Fermi...

Université de Neuchâtel

X-ray photoelectron diffraction study of Cu(1 1 1): Multiple scattering investigation

Despont, Laurent ; Naumovic, D. ; Clerc, Florian ; Koitzsch, Christian ; Garnier, Michael Bernard Gunnar ; Garcia de Abajo, F.J. ; Van Hove, M. A. ; Aebi, Philipp

In: Surface Science, 2006, vol. 600, no. 2, p. 380-385

Multiple scattering theory based on a cluster model is used to simulate full-hemispherical X-ray photoelectron diffraction measurements in order to verify how state of the art multiple scattering simulations are able to reproduce the experiment. This approach is applied to the Cu(1 1 1) surface for two different photoelectron kinetic energies. Differences and similarities between single and...

Université de Neuchâtel

Growth of thin Bi films on W(1 1 0)

Koitzsch, Christian ; Bovet, M. ; Clerc, Florian ; Naumovic, D. ; Schlapbach, Louis ; Aebi, Philipp

In: Surface Science, 2003, vol. 527, no. 1-3, p. 51-56

We report on the growth of single crystalline epitaxial Bi films on W(1 1 0). X-ray photoelectron diffraction (XPD) and low energy electron diffraction (LEED) reveal that Bi grows well ordered in the pseudocubic (0 0 1) orientation. The two-fold symmetric W(1 1 0) surface supports four different Bi(0 0 1) domains. The multi-domain nature is unambigously detected via LEED showing a peculiar...

Université de Neuchâtel

Geometrical and electronic structure of Pd clusters on graphite

Bovet, M. ; Boschung, E. ; Hayoz, J. ; Pillo, Th. ; Dietler, G. ; Aebi, Philipp

In: Surface Science, 2001, vol. 473, no. 1-2, p. 17-24

Pd clusters formed by physical vapor deposition at room temperature (RT) on highly oriented pyrolytic graphite were investigated by a combination of X-ray photoelectron spectroscopy and diffraction, angle-resolved ultraviolet photoelectron spectroscopy, scanning tunneling microscopy and calculations based on the local density functional theory. Different coverages with nominally 3, 5 and 10 Å...

Université de Neuchâtel

Oxidation of Al–Pd–Mn quasicrystal surfaces

Popovic, D. ; Naumovic, D. ; Bovet, M. ; Koitzsch, Christian ; Schlapbach, Louis ; Aebi, Philipp

In: Surface Science, 2001, vol. 492, no. 3, p. 294-304

The oxidation of both, quasicrystalline and crystalline surfaces of an icosahedral Al–Pd–Mn quasicrystal cut perpendicular to its five-fold axis and of Al(1 1 1) has been studied by means of X-ray photoelectron spectroscopy, ultraviolet photoemission spectroscopy, low-energy electron diffraction and X-ray photoelectron diffraction. The oxidation of the elements of the alloy is quantified and...

Université de Neuchâtel

Temperature-induced phase transition observed at a fivefold icosahedral quasicrystalline AlPdMn surface

Naumovic, D. ; Aebi, Philipp ; Beeli, C. ; Schlapbach, Louis

In: Surface Science, 1999, vol. 433-435, p. 302-306

A switch in symmetry from fivefold to tenfold has been observed at the surface of a monograin icosahedral AlPdMn quasicrystal cut perpendicularly to a fivefold axis as a function of annealing temperature and/or annealing time at a constant temperature. A continuous change in stoichiometry was simultaneously monitored by X-ray photoelectron spectroscopy. The surface structure study was performed...

Université de Neuchâtel

Growth of Au on Ag(110): electronic structure by photoemission

Hayoz, J. ; Pillo, Th. ; Naumovic, D. ; Aebi, Philipp ; Schlapbach, Louis

In: Surface Science, 1999, vol. 433-435, p. 104-108

Au films, from the submonolayer range up to eight monolayers, have been deposited in situ at 300 K. The electronic structure has been probed by ultra-violet valence-band photoemission. The discussion of our findings is based on a detailed knowledge of the geometrical structure of each film. With increasing Au coverage the valence-band structure changes from Ag- to Au-bulk-like. At intermediate Au...