Coherent optical phonons in different phases of Ge[sub 2]Sb[sub 2]Te[sub 5] upon strong laser excitation

Abstract : The transient reflectivity response of phase-change Ge2Sb2Te5 films to intense femtosecond laser pulses is studied by ultrafast coherent phonon spectroscopy. The three different phases (amorphous, fcc-, and hcp-crystalline), as well as laser-crystallized films, are investigated, featuring different photoexcited carrier and coherent optical phonon dynamics. At least two main phonon frequencies are identified for each phase/material and their evolution for increasing pump fluences is investigated for the fcc-crystalline phase and the laser-crystallized material, revealing strong differences. We find evidence that a considerable fraction of amorphous phase remains in the laser-crystallized material, which features a different phonon frequency, not related to other phases. These results are important for emerging strategies aimed at driving ultrafast phase transitions via coherent phonon excitation for applications in data storage. (C) 2011 American Institute of Physics. [doi:10.1063/1.3601478]
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Applied Physics Letters, American Institute of Physics, 2011, 98 (25), 〈10.1063/1.3601478〉
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Soumis le : mercredi 30 novembre 2016 - 10:46:28
Dernière modification le : jeudi 10 mai 2018 - 01:58:47

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J. Hernandez-Rueda, A. Savoia, W. Gawelda, J. Solis, B. Mansart, et al.. Coherent optical phonons in different phases of Ge[sub 2]Sb[sub 2]Te[sub 5] upon strong laser excitation. Applied Physics Letters, American Institute of Physics, 2011, 98 (25), 〈10.1063/1.3601478〉. 〈hal-01405554〉

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