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Université de Fribourg

Structure and stability of the Si(331)-(12×1) surface reconstruction investigated with first-principles density functional theory

Battaglia, Corsin ; Onida, Giovanni ; Gaál-Nagy, Katalin ; Aebi, Philipp

In: Physical Review B: condensed matter and materials physics, 2009, vol. 80, no. 21, p. 214102

We recently proposed a structural model for the Si(331)-(12×1) surface reconstruction containing silicon pentamers and adatoms as elementary structural building blocks. Using first-principles density functional theory we here investigate the stability of a variety of adatom configurations and determine the lowest-energy configuration. We also present a detailed comparison of the energetics...

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

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...

Université de Neuchâtel

NEA peak of the differently terminated and oriented diamond surfaces

Diederich, L. ; Aebi, Philipp ; Küttel, O. M. ; Schlapbach, Louis

In: Surface Science Letters, 1999, vol. 424, no. 2-3, p. L314-L320

The negative electron affinity (NEA) peak of differently terminated and oriented diamond surfaces is investigated by means of ultraviolet photoemission spectroscopy. Electron emission measurements in the range below the conduction band minimum (CBM) up to the vacuum level Evac permit the quantitative calculation of the upper limit of the NEA value. The inelastic scattering at the surface to the...

Université de Neuchâtel

Photoelectron emission from nitrogen- and boron-doped diamond (100) surfaces

Diederich, L. ; Küttel, O. M. ; Ruffieux, P. ; Pillo, Th. ; Aebi, Philipp ; Schlapbach, Louis

In: Surface Science, 1998, vol. 417, no. 1, p. 41-52

The nitrogen-doped (N-doped), type Ib, synthetic diamond (100) surface was investigated by means of X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). Photoelectron emission data from the boron-doped (B-doped) and the N-doped diamond (100) surfaces were compared and permitted the energy band diagrams for these differently terminated surfaces to be drawn. We...

Université de Neuchâtel

Angle-scanned photoemission: Fermi surface mapping and structural determination

Aebi, Philipp ; Fasel, Roman ; Naumovic, D. ; Hayoz, J. ; Pillo, Th. ; Bovet, M ; Agostino, R. G. ; Patthey, L. ; Schlapbach, Louis ; Gil, F. P. ; Berger, Helmuth ; Kreutz, T. J. ; Osterwalder, Jürg

In: Surface Science, 1998, vol. 402-404, p. 614-622

A brief survey of the angle-scanned photoemission technique is given. It incorporates two complementary methods in one: 1. Mapping of X-ray excited photoelectron intensities over virtually the complete hemisphere above the sample surface results in extended data sets where important surface-geometrical structure information is extracted and even “fingerprinting” is possible. This...

Université de Neuchâtel

Angle-scanned photoemission on YbHx: relevance for switchable mirrors

Hayoz, J. ; Koitzsch, C. ; Popovic, D. ; Bovet, M. ; Naumovic, D. ; Aebi, Philipp

In: Surface Review and Letters (SRL), 2002, vol. 9, no. 1, p. 235-241

Yttrium, lantanum and rare earth elements can be loaded with hydrogen inducing a metal–insulator transition and giving rise to optical switching from reflecting to transparent. We present angle-scanned photoemission experiments characterizing thin YbHx films grown on W(110) at room temperature. Hydrogen loading is performed in an ultrahigh-vacuum-compatible high pressure (1 bar)...