Phonons in slow motion: Dispersion relations in ultrathin Si membranes

John Cuffe, Emigdio Chávez, Andrey Shchepetov, Pierre Olivier Chapuis, El Houssaine El Boudouti, Francesc Alzina, Timothy Kehoe, Jordi Gomis-Bresco, Damian Dudek, Yan Pennec, Bahram Djafari-Rouhani, Mika Prunnila, Jouni Ahopelto, Clivia M. Sotomayor Torres

Research output: Contribution to journalArticleResearchpeer-review

74 Citations (Scopus)


We report the changes in dispersion relations of hypersonic acoustic phonons in free-standing silicon membranes as thin as ∼8 nm. We observe a reduction of the phase and group velocities of the fundamental flexural mode by more than 1 order of magnitude compared to bulk values. The modification of the dispersion relation in nanostructures has important consequences for noise control in nano- and microelectromechanical systems (MEMS/NEMS) as well as opto-mechanical devices. © 2012 American Chemical Society.
Original languageEnglish
Pages (from-to)3569-3573
JournalNano Letters
Issue number7
Publication statusPublished - 11 Jul 2012


  • Confined phonons
  • dispersion relations
  • inelastic light scattering
  • Si membranes
  • slow phonons
  • ultrathin


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