Effect of phonon confinement on the dispersion relation and heat capacity in nanoscale Si membranes

J. Cuffe, E. Chávez, Andrey Shchepetov, P.-O. Chapuis, E.H. El Boudouti, F. Alzina, Y. Pennec, B. Djafari-Rouhani, Mika Prunnila, Jouni Ahopelto, C.M. Sotomayor Torres

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

    Abstract

    The effect of confinement on the acoustic phonon dispersion relation and heat capacity in free-standing silicon membranes is investigated, with thickness values down ~ 8 nm. The discrete phonon branches are observed by angle-resolved inelastic light scattering spectroscopy. The fundamental flexural mode was observed to have a scattering intensity nearly two orders of magnitude larger than the fundamental dilatational mode, which is ascribed to its large out-of-plane density of states and quadratic dispersion. The quadratic dispersion also results in a reduction of the phase and group velocities of the fundamental flexural mode by more than one order of magnitude compared to bulk values. To investigate the effect of this behavior on the thermal conductivity, we perform calculations based on continuum elasticity theory to estimate corresponding changes in the heat capacity. This work provides a basis to investigate the effects of the frequency and dimension dependence of other phonon properties, in particular in the sub-20 nm regime, where phonon-phonon relaxation times, density of states and thermal conductivity are expected to possess different spectral dependencies than for bulk materials.
    Original languageEnglish
    Title of host publicationASME 2012 International Mechanical Engineering Congress and Exposition
    Subtitle of host publicationVolume 9: Micro- and Nano-Systems Engineering and Packaging, Parts A and B
    PublisherAmerican Society of Mechanical Engineers (ASME)
    Pages1081-1088
    Volume9
    ISBN (Print)978-0-7918-4525-7
    DOIs
    Publication statusPublished - 2012
    MoE publication typeA4 Article in a conference publication
    EventASME 2012 International Mechanical Engineering Congress and Exposition, IMECE 2012 - Houston, TX, United States
    Duration: 9 Nov 201215 Nov 2012

    Conference

    ConferenceASME 2012 International Mechanical Engineering Congress and Exposition, IMECE 2012
    Abbreviated titleIMECE 2012
    CountryUnited States
    CityHouston, TX
    Period9/11/1215/11/12

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