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arXiv · 1209.2174

Lifetimes of Confined Acoustic Phonons in Ultra-Thin Silicon Membranes

J. Cuffe·O. Ristow·E. Chávez·A. Shchepetov·P-O. Chapuis·F. Alzina·M. Hettich·M. Prunnila·J. Ahopelto·T. Dekorsy·C. M. Sotomayor Torres
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Abstract

We study the relaxation of coherent acoustic phonon modes with frequencies up to 500 GHz in ultra-thin free-standing silicon membranes. Using an ultrafast pump-probe technique of asynchronous optical sampling, we observe that the decay time of the first-order dilatational mode decreases significantly from \sim 4.7 ns to 5 ps with decreasing membrane thickness from \sim 194 to 8 nm. The experimental results are compared with theories considering both intrinsic phonon-phonon interactions and extrinsic surface roughness scattering including a wavelength-dependent specularity. Our results provide insight to understand some of the limits of nanomechanical resonators and thermal transport in nanostructures.

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J. Cuffe, O. Ristow, E. Chávez, A. Shchepetov, P-O. Chapuis, F. Alzina, M. Hettich, M. Prunnila, J. Ahopelto, T. Dekorsy, C. M. Sotomayor Torres. 2012-09-10. Lifetimes of Confined Acoustic Phonons in Ultra-Thin Silicon Membranes. https://doi.org/10.1103/physrevlett.110.095503

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