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(114) Production(s) de LE PARC R.
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In situ high pressure and high temperature Raman studies of (1-x)SiO2xGeO2 glasses 
Auteur(s): Le Parc R., Ranieri Vincent, Haines Julien, Cambon Martine, Cambon Olivier, Levelut C., Clement S.
(Article) Publié:
Journal Of Physics: Condensed Matter, vol. 21 p.375109 (2009)
Ref HAL: hal-00434405_v1
PMID 21832340
DOI: 10.1088/0953-8984/21/37/375109
WoS: 000269198900011
Exporter : BibTex | endNote
9 Citations
Résumé: The structure of glasses in the binary system SiO2-GeO2 has been studied by Raman spectroscopy. Our results are consistent with mixing of SiO2 and GeO2 tetrahedra. The changes induced by temperature and by pressure on the structure are monitored by in situ measurements on the same mixed glasses. Anomalous temperature dependences are observed not only for SiO2 glass and GeO2 glass but also for mixed glasses. Particular attention is focused on the pressure densification mechanism in mixed glasses. Via the pressure dependence of the width of the main Raman band, we show that the compression mechanism in mixed glasses is intermediate between that of the end members.
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Raman scattering study of alpha-quartz and Si(1-x)GexO2 solid solutions
Auteur(s): Ranieri Vincent, Bourgogne David, Darracq S., Cambon Martine, Haines Julien, Cambon Olivier, Le Parc R., Levelut C., Largeteau Alain, Demazeau Gérard
(Article) Publié:
Physical Review B, vol. 79 p.224304 (2009)
Ref HAL: hal-00434422_v1
DOI: 10.1103/PhysRevB.79.224304
WoS: 000267699300052
Exporter : BibTex | endNote
30 Citations
Résumé: alpha-quartz-type Si1−xGexO2 solid solutions (x=0.06, 0.11, and 0.24) and pure SiO2 were investigated by Raman spectroscopy. Coupled and decoupled vibrational modes were identified at room temperature as a function of composition. Tetrahedral tilting librational modes involved in the displacive alpha<-->beta-quartz phase transition are decoupled. The wave number of the coupled A1 mode located at 464 cm−1 for pure alpha-quartz was found to vary quite linearly with germanium content. Raman spectra were recorded up to 1473 K. Substitution of germanium in the quartz lattice clearly improves the thermal stability of the alpha phase. The alpha<-->beta-quartz phase transition temperature increases from 846±1 K for x=0 to about 1300±50 K for x=0.24. At the same time, the dynamic disorder observed in quartz well below the transition is reduced in the solid solutions.
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Etude Raman sous pression de verres binaires germano silicates
Auteur(s): Le Parc R., Haines Julien, Ranieri Vincent, Cambon Martine, Cambon Olivier, Levelut C.
Conference: 6ième Forum de technologie des hautes pressions: Les verrous technologiques dans l'expérimentation h (Bat, FR, 2008-10-06)
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In situ and ex situ studies of pressure-induced amorphization in zeolites
Auteur(s): Haines Julien, Isambert Aude, Angot Emmanuel, Hébert Philippe, Levelut C., Le Parc R., Oshishi Y, Kohara Shinji, Keen David, Hammouda Tahar, Andrault Denis
Conference: 46th EHPRG Conference (Valencia, ES, 2008-09-07)
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Pressure-induced phase transition in phase-change memory alloy
Auteur(s): Levelut C., Krbal Milos, Haines Julien, Kolobov Alex, Pradel Annie, Ribes Michel, Le Parc R., Fons Paul, Tominaga J., Hanfland Michael
Conference: 46th EHPRG Conference (Valencia, ES, 2008-09-07)
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Density and concentration fluctuations in SiO2-GeO2 optical fiber glass investigated by small angle x-ray scattering
Auteur(s): Le Parc R., Champagnon Bernard, Levelut C., Martinez Valérie, David Laurent, Faivre A., Flammer Ivo, Hazemann Jean-Louis, Simon J.
(Article) Publié:
Journal Of Applied Physics, vol. 103 p.094917 (2008)
Ref HAL: hal-00385046_v1
Exporter : BibTex | endNote
Résumé: Density and concentration fluctuations have been investigated in a 3 mol % GeO2 doped silica glass as a function of the fictive temperature (the temperature at which the structure of the supercooled liquid has been frozen-in to form the glass) by small angle x-ray scattering measurements. The fluctuations increase in a way is quite similar to that observed for pure silica glass as a result of density fluctuation fictive temperature dependence. Fluctuations have also been studied in glasses containing different amounts of GeO2 up to 21 mol % GeO2. The fluctuations are shown to increase very strongly with germanium amount as a result of strong concentration fluctuation increase. This observation is in agreement with already observed excess losses in light scattering measurements.
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Temperature independence of pressure-induced amorphization of the phase-change memory alloy Ge2Sb2Te5
Auteur(s): Krbal Milos, Kolobov Alex, Haines Julien, Annie Pradel, Michel Ribes, Paul Fons, Tominaga J., Levelut C., Le Parc R., Hanfland Michael
(Article) Publié:
Applied Physics Letters, vol. 93 p.031918 (2008)
Ref HAL: hal-00341455_v1
DOI: 10.1063/1.2956409
WoS: 000257968700035
Exporter : BibTex | endNote
29 Citations
Résumé: n the temperature range from room temperature to about 150 °C, the prototypic phase-change material Ge2Sb2Te5 becomes amorphous upon hydrostatic compression. In the studied temperature range, the onset of amorphization is at about 15 GPa and the material completely amorphizes at 25 GPa; these values do not depend on temperature. Upon decompression, the amorphous phase is stable at lower temperatures, yet at higher temperatures (145 °C), the initial fcc phase is recovered upon decompression. A possible mechanism of pressure-induced amorphization and its implications for phase-change memories are discussed.
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