Abstract
Quasiballistic heat conduction from nanoscale heat sources of size comparable to phonon mean free paths has recently become of intense interest both scientifically and for its applications. Prior work has established that, in the quasiballistic regime, the apparent thermal properties of materials depend both on intrinsic mechanisms and the characteristics of the applied thermal gradient. However, many aspects of this regime remain poorly understood. Here, we experimentally study the thermal response of crystals to large thermal gradients generated by optical heating of nanoline arrays. Our experiments reveal the key role of the spatial frequencies and Fourier series amplitudes of the heating profile for thermal transport in the quasiballistic regime, in contrast to the conventional picture that focuses on the geometric dimensions of the individual heaters. Our work provides the insight needed to rationally mitigate local hot spots in modern applications by manipulating the spatial frequencies of the heater patterns.
Original language | English |
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Article number | 054068 |
Journal | Physical Review Applied |
Volume | 10 |
Issue number | 5 |
DOIs | |
State | Published - Nov 29 2018 |
Funding
The authors thank Alexei Maznev for valuable comments and discussions; Lucas Lindsay for providing the first-principles calculations for silicon; the Kavli Nanoscience (KNI) at Caltech for the availability of critical cleanroom facilities; Guy A. DeRose for discussions and comments on the nanoline array fabrications; Matt H. Sullivan for assistance on FIB and e-beam lithography processing; Carol M. Carland for TEM assistance; and Bo Sun and Peishi Cheng for proofreading the article. This work was sponsored in part by the National Science Foundation under Grant No. CBET CAREER 1254213 and by Boeing under the Boeing-Caltech Strategic Research & Development Relationship Agreement. H.Z. also gratefully acknowledges the financial support of the CAS Pioneer Hundred Talents Program.