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Université de Neuchâtel

Substitution sites of Pb and Y in Bi2Sr2Ca1Cu2O8+δ : X-ray photoelectron diffraction as fingerprinting tool

Pillo, Th. ; Hayoz, J. ; Schwaller, P. ; Berger, H. ; Aebi, Philipp ; Schlapbach, Louis

In: Applied Physics Letters, 1999, vol. 75, no. 11, p. 1550-1552

The substitution site of Y and Pb in the cuprate-type high temperature superconductor Bi2Sr2Ca1Cu2O8+δ is determined in a very direct and unambiguous way by means of angle-scanned x-ray photoelectron diffraction (XPD). Using XPD as a fingerprinting tool, we conclude that Y occupies the Ca sites and Pb the Bi sites, respectively. Furthermore,...

Université de Neuchâtel

Switchable yttrium–hydride mirrors grown on CaF2 (111): A x-ray photoelectron spectroscopy and diffraction study

Hayoz, J. ; Schoenes, J. ; Schlapbach, Louis ; Aebi, Philipp

In: Journal of Applied Physics, 2001, vol. 90, no. 8, p. 3925-3933

The epitaxial growth of Y (hydride) films on CaF2 (111) has been investigated using x-ray photoelectron spectroscopy, x-ray photoelectron diffraction, and low energy electron diffraction (LEED). For Y deposition at 700 °C the formation of high-quality epitaxial hcp(0001) oriented Y films is observed. Whenever the Y films showed good surface quality, the surface is rich in F. Only when...

Université de Neuchâtel

A chemical state resolved x-ray photoelectron diffraction study: Initial stages in diamondlike carbon film deposition

Agostino, R. G. ; Küttel, O. M. ; Aebi, Philipp ; Fasel, R. ; Osterwalder, J. ; Schlapbach, Louis

In: Journal of Applied Physics, 1996, vol. 80, no. 4, p. 2181-2186

The structural sensitivity of x-ray photoelectron diffraction is greatly enhanced by the acquisition of a full hemispherical diffraction pattern of chemically shifted core levels. Complex systems can be studied resolving the local order per element and per chemical environment. This technique is applied to study the earliest stages of hydrogenated diamondlike carbon film deposition on Si(001)....

Université de Neuchâtel

X-ray photoelectron diffraction of (100)-oriented chemical vapor deposited diamond films on silicon (100)

Schaller, E. ; Küttel, O. M. ; Aebi, Philipp ; Schlapbach, Louis

In: Applied Physics Letters, 1995, vol. 67, no. 11, p. 1533-1534

(100)-oriented diamond films have been grown on silicon (100) in a microwave plasma assisted chemical vapor deposition (CVD) tubular system. X-ray photoelectron diffraction (XPD) has been used to study such oriented polycrystalline films. Comparing the diffractograms of a natural diamond (100) surface and of polycrystalline (100)-oriented CVD diamond films quite similar features are observed. XPD...

Université de Neuchâtel

X-ray absorption fine structure studies of buried Ge-Si interfaces

Aebi, Philipp ; Tyliszczak, T. ; Hitchcock, A. P. ; Jackman, T. E. ; Baribeau, J.-M.

In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1991, vol. 9, no. 3, p. 907-911

We have used Ge A-edge x-ray absorption fine structure (EXAFS) and a gas ionization detector with sample rotation to study the local environment of nominally pure Qe layers buried in single crystal Si. The samples were grown by molecular-beam epitaxy on Si( 100). The dependence on thickness, number of Ge layers and growth temperature is explored. Considerable sensitivity to the quality of the...

Université de Neuchâtel

Preparation and characterization of clean, single-crystalline YHx films (0≤x≤2.9) on W(110)

Hayoz, J. ; Pillo, T. ; Bovet, M. ; Guthrie, St. ; Pastore, G. ; Schlapbach, Louis ; Aebi, Philipp

In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2000, vol. 18, no. 5, p. 2417-2431

Yttrium can be loaded with hydrogen up to high concentrations causing dramatic structural and electronic changes of the host lattice. We report on the preparation of clean, single-crystalline YHx films (0≤x≤2.9). The films have been characterized in situ combining angle-resolved photoelectron spectroscopy (ARPES) and low energy electron diffraction. Direct Y dihydride...

Université de Neuchâtel

Doping-dependent electronic structure of cuprates studied using angle-scanned photoemission

Schwaller, P. ; Greber, T. ; Aebi, Philipp ; Singer, J. M. ; Berger, H. ; Forró, L. ; Osterwalder, J.

In: The European Physical Journal B - Condensed Matter and Complex Systems, 2000, vol. 18, no. 2, p. 215-225

Full k ||-maps of the electronic structure near the Fermi level of differently doped cuprates measured with angle-scanned photoelectron spectroscopy are presented. The valence band maximum of the antiferromagnetic insulator Sr2CuO2Cl2, which is taken as a representative of an undoped cuprate, and the Fermi surfaces of overdoped, optimally doped and...

Université de Neuchâtel

Oxygen-segregation-controlled epitaxy of Y2O3 films on Nb(110)

Hayoz, J. ; Bovet, M. ; Pillo, T. ; Schlapbach, Louis ; Aebi, Philipp

In: Applied Physics A: Materials Science & Processing, 2000, vol. 71, no. 6, p. 615-618

We demonstrate a very simple and reliable method of manufacturing clean, single-crystalline Y2O3 films on Nb(110) substrates in situ. The method exploits the oxygen bulk contamination of Nb as a source of clean oxygen. For substrate temperatures above 800 K oxygen segregation to the Nb surface is so efficient, that yttrium becomes oxidized during deposition without any...

Université de Neuchâtel

Non-uniform doping across the Fermi surface of NbS2 intercalates

Battaglia, Corsin ; Cercellier, H. ; Despont, L. ; Monney, Claude ; Prester, M. ; Berger, H. ; Forró, L. ; Garnier, Michael Bernard Gunnar ; Aebi, Philipp

In: The European Physical Journal B - Condensed Matter and Complex Systems, 2007, vol. 57, no. 4, p. 385-390

Magnetic ordering of the first row transition metal intercalates of NbS2 due to coupling between the conduction electrons and the intercalated ions has been explained in terms of Fermi surface nesting. We use angle-resolved photoelectron spectroscopy to investigate the Fermi surface topology and the valence band structure of the quasi-two-dimensional layer compounds...

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)...