Lifetimes of confined acoustic phonons in ultrathin silicon membranes

J. Cuffe, O. Ristow, E. Chávez, Andrey Shchepetov, P.-O. Chapuis, F. Alzina, M. Hettich, Mika Prunnila, Jouni Ahopelto, T. Dekorsy, C.M. Sotomayor Torres (Corresponding Author)

    Research output: Contribution to journalArticleScientificpeer-review

    96 Citations (Scopus)


    We study the relaxation of coherent acoustic phonon modes with frequencies up to 500 GHz in ultrathin 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 ∼4.7  ns to 5 ps with decreasing membrane thickness from ∼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.
    Original languageEnglish
    Article number095503
    Number of pages5
    JournalPhysical Review Letters
    Issue number9
    Publication statusPublished - 2013
    MoE publication typeA1 Journal article-refereed


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