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(107) Production(s) de FORET M.
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Observation of the onset of strong scattering on high frequency acoustic phonons in densified silica glass 
Auteur(s): Ruffle B., Foret M., Courtens E., Vacher R., Monaco G.
(Article) Publié:
Physical Review Letters, vol. 90 p.095502 (2003)
Texte intégral en Openaccess : 
Ref HAL: hal-00117305_v1
Ref Arxiv: cond-mat/0301490
Ref. & Cit.: NASA ADS
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Résumé: The linewidth of longitudinal acoustic waves in densified silica glass is obtained by inelastic x-ray scattering. It increases with a high power alpha of the frequency up to a crossover where the waves experience strong scattering. We find that \alpha is at least 4, and probably larger. Resonance and hybridization of acoustic waves with the boson-peak modes seems to be a more likely explanation for these findings than Rayleigh scattering from disorder.
Commentaires: 4 pages, 4 figures
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Imaging the composition of oxide-glass surfaces by friction atomic force microscopy
Auteur(s): Destouches N., Foret M., Courtens E., Ramonda M.
(Article) Publié:
Langmuir, vol. 19 p.6570-6572 (2003)
Résumé: Fracture surfaces of high-purity silica glasses, finely patterned with small amounts of either GeO2 or P2O5 substituted for SiO2, are investigated by atomic force microscopy under an electrolyte. The samples are cross sections of graded-index optical fibers of the type used for long-distance optical communications. While topography images are featureless, the frictional force is strikingly sensitive to the composition, down to similar to0.1% for the [P]/[Si] ratio. This unexpectedly large contrast depends on the pH of the electrolyte showing its relation to the acid-base properties of the oxides. This result holds considerable promise for the local exploration of acid-base properties of mixed oxides down to the nanometer scale.
Commentaires: English Article 711YL
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The crossover from propagating to strongly scattered acoustic modes of glasses observed in densified silica
Auteur(s): Courtens E., Foret M., Hehlen B., Ruffle B., Vacher R.
(Article) Publié:
Journal Of Physics: Condensed Matter, vol. 15 p.S1279-S1290 (2003)
Résumé: Spectroscopic results on low-frequency excitations of densified silica are presented and related to characteristic thermal properties of glasses. The end of the longitudinal acoustic branch is marked by a rapid increase of the Brillouin linewidth with the scattering vector. This rapid growth saturates at a crossover frequency Omega(co) which nearly coincides with the centre of the boson peak. The latter is clearly due to additional optic-like excitations related to nearly rigid SiO4 librations as indicated by hyper-Raman scattering. Whether the onset of strong scattering is best described as resulting from hybridization of acoustic modes with these librations, from their elastic scattering (Rayleigh scattering) on the local excitations, or from, soft potentials remains to be established.
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What can we learn the long-range structure of glasses from relaxations and vibrations ?
Auteur(s): Vacher R., Courtens E., Foret M., Hehlen B., Ruffle B.
Conference: 2 nd International Symposium on Non-Crystalline Solids (Campos do Jordao, Brazil, FR, 2003-09-21)
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The boson peak of oxide glasses and its relation with the end of acoustic branches
Auteur(s): Hehlen B., Ruffle B., Foret M., Vacher R., Courtens E.
Conference: 4th Congres de la Societe Venezuelienne de Physique (Ile Margarita, Venezuela, FR, 2003-09-24)
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High frequency sound in glasses
Auteur(s): Courtens E., Foret M., Hehlen B., Ruffle B., Vacher R.
Conference: 2nd International Conference on Materials for Advanced Technologies, Symposium J on Synchrotron Radiation for Advanced Materials Analysis and Processing (Singapore, FR, 2003-12-07)
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Merging of the acoustic branch with the boson peak in densified silica glass
Auteur(s): Foret M., Vacher R., Courtens E., Monaco G.
(Article) Publié:
Physical Review B, vol. 66 p.024204 (2002)
Résumé: Both high-frequency acoustic modes and the boson peak related to SiO4 librations are observed in a single inelastic x-ray scattering experiment. The experimental data are consistent with a picture where the acoustic modes experience a crossover at a frequency Omega(co) beyond which plane waves cease to exist. The spectra evolve with the scattering vector to merge into a broad boson peak at Omega(BP)approximate toOmega(co). The latter, although essentially optic in nature, might hybridize with the resonant acousticlike modes, which can be crucial to their strong scattering.
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