Direct measurement of room-temperature nondiffusive thermal transport over micron distances in a silicon membrane

Jeremy A. Johnson, A. A. Maznev, John Cuffe, Jeffrey K. Eliason, Austin J. Minnich, Timothy Kehoe, Clivia M Sotomayor Torres, Gang Chen, Keith A. Nelson

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276 Scopus citations

Abstract

The "textbook" phonon mean free path of heat carrying phonons in silicon at room temperature is ∼40 nm. However, a large contribution to the thermal conductivity comes from low-frequency phonons with much longer mean free paths. We present a simple experiment demonstrating that room-temperature thermal transport in Si significantly deviates from the diffusion model already at micron distances. Absorption of crossed laser pulses in a freestanding silicon membrane sets up a sinusoidal temperature profile that is monitored via diffraction of a probe laser beam. By changing the period of the thermal grating we vary the heat transport distance within the range ∼1-10 μm. At small distances, we observe a reduction in the effective thermal conductivity indicating a transition from the diffusive to the ballistic transport regime for the low-frequency part of the phonon spectrum.

Original languageEnglish (US)
Article number025901
JournalPhysical review letters
Volume110
Issue number2
DOIs
StatePublished - Jan 8 2013

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