Direct measurement of room-temperature nondiffusive thermal transport over micron distances in a silicon membrane
Johnson, Jeremy A.
Maznev, A. A.
Eliason, Jeffrey K.
Minnich, Austin J.
Sotomayor Torres, Clivia M.
Nelson, Keith A.
American Physical Society
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
Thin films , Conduction , Scattering , Gratings , Dynamics , Carrier
Johnson, J. A., Maznev, A. A., Cuffe, J., Eliason, J. K., Minnich, A. J., Kehoe, T., Torres, C. M. S., Chen, G. and Nelson, K. A. (2013) 'Direct measurement of room-temperature nondiffusive thermal transport over micron distances in a silicon membrane', Physical Review Letters, 110(2), 025901 (5pp). doi: 10.1103/PhysRevLett.110.025901
© 2013, American Physical Society