%0 Conference Paper
%F Oral 
%T Temperature dependence of hypersound attenuation in silica films via picosecond acoustics
%+ Laboratoire Charles Coulomb (L2C)
%+ Institut des Nanosciences de Paris (INSP)
%+ Centre de Nanosciences et de Nanotechnologies [Marcoussis] (C2N)
%A Foret, Marie
%A Huynh, A.
%A Peronne, E.
%A Ruffle, Benoit
%A Perrin, B.
%A Lafosse, X.
%A Lemaitre, A.
%A Vacher, Rene
%< sans comité de lecture
%Z L2C:18-350
%B 16th International Conference on Phonon Scattering in Condensed Matter (Phonons 2018)
%C Nanjing, China
%8 2018-05-30
%D 2018
%Z Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other]Conference papers
%X We reinvestigate sound dispersion and attenuation in a SiO2 layer as a function of temperature over the range 20–300 K by picosecond acoustics [1]. A pulse-echo scheme is used, where a broadband strain-pulse (centered at 120 GHz) is detected in an Al transducer after propagating back and forth through the SiO2 layer. The acoustic attenuation coefficient α within the SiO2 layer is evaluated by fitting the echoes to a mismatch model including an effective local law for the frequency dependence of attenuation over the band of the pulse. In this way, the T dependence of α in SiO2 layers could be extracted in this work for the first time. Results are found to follow rather well a model combining coupling to thermally activated relaxation mechanisms and interactions with thermal vibrations. This leads to a non-trivial variation of the attenuation coefficient with frequency and temperature. The number density of relaxing defects in the SiO2 layer is found to be slightly higher than that in bulk v-SiO2. In contrast, similar anharmonic contribution to acoustic absorption is observed in both systems. The velocity variations are also measured and are compared to the dynamical velocity changes deduced from the sound attenuation.
%G English
%L hal-01940549
%U https://hal.science/hal-01940549
%~ CNRS
%~ UNIV-PSUD
%~ INSP
%~ ALLINSP
%~ L2C
%~ UNIV-PARIS-SACLAY
%~ UNIV-PSUD-SACLAY
%~ MIPS
%~ UNIV-MONTPELLIER
%~ SORBONNE-UNIVERSITE
%~ SORBONNE-UNIV
%~ SU-SCIENCES
%~ UP-SCIENCES
%~ GS-PHYSIQUE
%~ ALLIANCE-SU
%~ UM-2015-2021
%~ C2N