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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

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

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

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

Structural characterization of submonolayer C/Al(111)

Scalese, S. ; Agostino, R. G. ; Hayoz, J. ; Naumovic, D. ; Fasel, Roman ; Aebi, Philipp ; Schlapbach, Louis

In: Surface Science, 1998, vol. 395, no. 1, p. 120-129

We report on the adsorption of atomic C in submonolayer coverages on the Al(111) surface. The local order at the surface is studied for different thermal treatments by means of full-heimispherical X-ray photoelectron diffraction. Deposition at room temperature results in disordered C adsorption while an ordering process takes place after annealing above 475 K. We depict the structure of the...

Université de Neuchâtel

Growth of Ag on Cu(001) studied by full-hemispherical X-ray photoelectron diffraction

Hayoz, J. ; Naumovic, D. ; Fasel, Roman ; Aebi, Philipp ; Schlapbach, Louis

In: Surface Science, 1997, vol. 373, no. 2-3, p. 153-172

Ag films, from the submonolayer range up to 14 monolayers (ML), have been deposited in situ on two differently cut Cu(001) single crystals. Their geometrical structure has been investigated by full-hemispherical X-ray photoelectron diffraction and by low-energy electron diffraction. Structural models developed on the basis of these data have been compared to single-scattering cluster...

Université de Neuchâtel

Real space mapping of the surface atomic environment via low energy scattering spectroscopy

Agostino, R. G. ; Aebi, Philipp ; Osterwalder, Jürg ; Hayoz, J. ; Schlapbach, Louis

In: Surface Science, 1997, vol. 384, no. 1-3, p. 36-45

Low-energy ion scattering spectroscopy is used to obtain real space surface imaging of the atomic surroundings of different fcc metal surfaces. Scattered He+ ions were mapped over a large solid angle sector. By using an universal shadow cone expression, it is possible to invert the angular maps into two-dimensional real space maps. The inversion procedure is tested on Pt(111), Cu(001)...

Université de Neuchâtel

Structure of Si atomic chains grown on the Si/Cu(110) c (2×2) surface alloy

Polop, C. ; Rojas, C. ; Martín-Gago, J. A. ; Fasel, Roman ; Hayoz, J. ; Naumovic, D. ; Aebi, Philipp

In: Physical Review B, 2001, vol. 63, no. 115414, p. 1-9

The surface atomic structure of Si atomic chains grown on the Si/Cu(110) surface alloy has been investigated by a combination of different experimental techniques. For Si coverages below 0.5 monolayers the low-energy electron diffraction (LEED) pattern shows a c(2×2) reconstruction, corresponding to the formation of a surface alloy. Upon further Si deposition, the LEED pattern evolves toward a...

Université de Neuchâtel

Fine structure in high-resolution photoemission spectra of quasi-two-dimensional 1T-TaS2

Pillo, Th. ; Hayoz, J. ; Naumovic, D. ; Berger, Helmuth ; Perfetti, L. ; Gavioli, L. ; Taleb-Ibrahimi, A. ; Schlapbach, Louis ; Aebi, Philipp

In: Physical Review B, 2001, vol. 64, no. 245105, p. 1-4

Using high-resolution angle-resolved photoemission spectroscopy (ARPES), we examined the charge density wave (CDW) compound 1T-TaS2 as a function of the photon energy (energy range from 11 up to 33 eV) for both quasicommensurate (QC) and commensurate (C) CDW phases. While the QC-phase normal emission ARPES spectra coincide with previous results, normal emission spectra of the C...

Université de Neuchâtel

Photoemission of bands above the Fermi level: The excitonic insulator phase transition in 1T-TiSe2

Pillo, Th. ; Hayoz, J. ; Berger, Helmuth ; Lévy, F. ; Schlapbach, Louis ; Aebi, Philipp

In: Physical Review B, 2000, vol. 61, no. 23, p. 16213-16222

High-resolution angle-resolved photoemission spectroscopy (ARPES) was used to investigate the transition metal dichalcogenide (TMC) 1T-TiSe2 above and below the phase transition. We find that this system fulfills special conditions such as narrow band width and flat dispersion for bands within 5kBT of the Fermi energy. These prerequisites allow ARPES to observe...