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International audience; We report on a complete elastic characterization by picosecond ultrasonics technique of lithium phosphorous oxynitride (LiPON) thin films, which are nowadays, considered as promising solid-state electrolytes for microbatteries technology. Longitudinal sound velocity is deduced from Brillouin oscillation detection at variable incidence angles. The density is estimated through an interfacial energy analysis related to the echo amplitude decay. Transverse wave velocity is obtained across the dispersion curve of Rayleigh surface waves. Combining these different approaches, Young's modulus and Poisson's ratio of LiPON are finally found to be 79 GPa and 0.27, respectively. (C) 2013 Elsevier B. V. All rights reserved.

International audience; We present a new method to measure without any calibration the thermal effusivity, conductivity, and diffusivity of an insulating layer deposited on a substrate, using lateral heat diffusion. The method is applied to Lithium phosphorous oxynitride, a thin film solid-state electrolyte used in micro-batteries. (C) 2013 AIP Publishing LLC.

International audience; In this chapter we present the basics of heat transfer in composites. The first approach, called the effective medium method, averages in a suitable way over the conductivities of the constituents. This gives good results for sufficiently large particles. However, when the particles are smaller than the mean free path of the excitations carrying the heat, the implicit assumptions of the effective medium theory are no longer justified. One must then look at the way the particles scatter the energy carriers.

International audience; We present thermal conductivity measurements performed in three short-period (GaAs)_9(AlAs)_5 superlattices. The samples were grown at different temperatures, leading to different small scale roughness and broadening of the interfaces. The cross-plane conductivity is measured with a differential 3w method, at room temperature. The order of magnitude of the overall thermal conductivity variation is consistent with existing theoretical models, although the actual variation is smaller than expected.

We report on the acoustic attenuation in an AlPdMn icosahedral quasicrystal between 15 and 300 K, in the tens of GHz range. High frequency coherent longitudinal acoustic waves are excited and detected by an optical ``pump and probe'' technique, in an interferometric configuration. Our results reveal that, at high temperature $(Tg100\mathrm{K}),$ the acoustic attenuation is rather small, close to the attenuation in crystals and much smaller than in disordered solids. We stress that Akhieser processes (phonon-phonon interactions) must be active in quasicrystals and give the correct behavior and order of magnitude of the acoustic attenuation, at high temperature. At low temperature, departure from the standard behavior arising from phonon-phonon interaction is not understood.

International audience; Thermoreflectance experiments are sensitive to the thermal properties of thin layers deposited on substrates (conductivity and diffusivity). However, retrieving these properties from experimental data remains a difficult issue. The case of a conducting layer deposited on an insulating substrate was studied previously. We present here a mathematical and experimental analysis of the thermoreflectance response in the opposite case: an insulating layer on a conducting substrate. We show theoretically that conductivity and diffusivity can be determined independently thanks to a comparison with the substrate. The method is applied to experiments performed on a silicon substrate covered with a thin layer deposited by sputtering a titanium target. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3702823]

The existence in polystyrene of an internal-friction peak around 80 K at 50 MHz is reported. This peak displays many similarities with the peak observed in amorphous selenium. It is interpreted in the frame of the same model. We explain our results with thermal activated relaxation processes displaying a constant distribution of barrier heights between 0 and 600 K. We suggest that the observed peak is the resolution at high frequency of the e-shoulder which has been reported previously at much lower frequency.