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Theses

Étude par Acoustique Picoseconde des Vibrations Individuelles et Collectives de Nanostructures Organisées

Abstract : This thesis is devoted to the study of the acoustic modes of nanostructures ordered as lattices. The vibration's frequencies of nanostructures are in the hypersonic range (1 GHz-1 THz). Their lattice organization with sub-micronic repetition step leads to collective acoustic modes in the same frequency range. This work aims to demonstrate these modes. We used electronic lithography to fabricate two dimensionnal lattices of metallic nanocubes. Their vibrations were time-resolved by picosecond ultrasonics. This optical pump-probe technique can excite and detect acoustic waves at hypersonic frequencies. Two kinds of acoustic modes were demonstrated. The proper modes of the cubes and the collective modes of the whole assembly. Collective modes are studied in lattices sets of various repetition step. They propagate in the lattices plane with a discrete set of wavevectors. An analytical model can explain their frequency as a function of the system's geometric and elastic parameters. Eventually the detection of these modes is due to a new mechanism, probably linked to the excitation of surface plasmon resonances at the sample surface.
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https://tel.archives-ouvertes.fr/tel-00459422
Contributor : Jean-Francois Robillard <>
Submitted on : Tuesday, February 23, 2010 - 9:02:20 PM
Last modification on : Tuesday, December 8, 2020 - 3:32:33 AM
Long-term archiving on: : Friday, June 18, 2010 - 9:49:46 PM

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  • HAL Id : tel-00459422, version 1

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Jean-Francois Robillard. Étude par Acoustique Picoseconde des Vibrations Individuelles et Collectives de Nanostructures Organisées. Physique [physics]. Université des Sciences et Technologie de Lille - Lille I, 2008. Français. ⟨tel-00459422⟩

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