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Identification de propriétés thermiques et spectroscopie térahertz de nanostructures par thermoréflectance pompe-sonde asynchrone : Application à l'étude du transport des phonons dans les super-réseaux

Abstract : The work presented in this thesis deals with identification and control of the thermal and acoustic properties of high thermoelectric potential nanostructures called “superlattices”. This thesis is divided in three parts: The first part gives a theoretical description of thermal diffusion in insulating and semiconducting materials. We first broach the atomic description then the macroscopic view using the Thermal Quadrupole model. The end of this chapter deals with acoustic and thermal properties specific to superlattices. The second part describes and compares synchronous and asynchronous thermoreflectance techniques used to extract thermal properties of thin films and superlattices. We find that for the synchronous case signals are subject to artifacts which confound parameter estimations. For the asynchronous case, we find that lack of a mechanical translation stage removes these artifacts. We then investigate the sensitivity functions, and finally validate our identification method by estimation of the thermal conductivity of a SiO2 thin film. The third part presents the results of thermal parameter identification in SiGe superlattices. We show that thermal interfaces play a major role to in the overall thermal conductivity. We also study superlattices with Ge nanodots and show that for such structures we are able to obtain thermal conductivity values near the amorphous values. Moreover, the linear behavior of the thermal conductivity with period thickness shows that it is possible to control this value. Finally, we use Thermoreflectance to perform THz coherent phonon spectroscopy of superlattices, revealing the spectral selectivity of these nanostructures.
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https://hal.univ-lorraine.fr/tel-01535965
Contributor : Gilles Pernot <>
Submitted on : Friday, June 9, 2017 - 5:50:00 PM
Last modification on : Monday, January 22, 2018 - 11:02:02 AM
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Gilles Pernot. Identification de propriétés thermiques et spectroscopie térahertz de nanostructures par thermoréflectance pompe-sonde asynchrone : Application à l'étude du transport des phonons dans les super-réseaux. Science des matériaux [cond-mat.mtrl-sci]. Université de Bordeaux, 2010. Français. ⟨tel-01535965⟩

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