Temperature dependence of hypersound attenuation in silica films via picosecond acoustics

Marie Foret (1) , A. Huynh (2) , E. Peronne (2) , Benoit Ruffle (1) , B. Perrin (2) , X. Lafosse (3) , A. Lemaitre (3) , Rene Vacher (1)

1 L2C - Laboratoire Charles Coulomb
2 INSP - Institut des Nanosciences de Paris
3 C2N - Centre de Nanosciences et de Nanotechnologies [Marcoussis]

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.

Domaines: Autre [cond-mat.other]

Marie Foret, A. Huynh, E. Peronne, Benoit Ruffle, B. Perrin, et al.. Temperature dependence of hypersound attenuation in silica films via picosecond acoustics. 16th International Conference on Phonon Scattering in Condensed Matter (Phonons 2018), Lifa Zhang (Nanjing Normal University; Conference Chair), May 2018, Nanjing, China. ⟨hal-01940549⟩