Journal
PHYSICAL REVIEW LETTERS
Volume 110, Issue 2, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevLett.110.025901
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Funding
- S3TEC Energy Frontier Research Center
- U.S. Department of Energy, Office of Basic Energy Sciences [DE-SC0001299/DE-FG02-09ER46577]
- NANOPOWER [256959]
- TAILPHOX [233883]
- NANOFUNCTION [257375]
- ACPHIN [FIS2009-150]
- AGAUR [2009-SGR-150]
- ICREA Funding Source: Custom
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The textbook phonon mean free path of heat carrying phonons in silicon at room temperature is similar to 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 similar to 1-10 mu m. 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. DOI: 10.1103/PhysRevLett.110.025901
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