Thermal Conductivity Spectroscopy Technique to Measure Phonon Mean Free Paths

In the citing paper

“our calculation overpredicts the effective thermal conductivity for all pump diameters below T ¼ 150 K”

In the citing paper

“Similarly, while TDTR can be used to study non-equilibrium phenomena such as quasi-ballistic phonon transport 90, 91, 109-111 and electronphonon coupling 55 due to its ability to detect temperature evolutions at micrometer-scale and picosecond-scale resolutions, the majority of the experimental work in the literature deduced thermal properties based on Fourier's”

In the citing paper

“Secondly, the phonon MFPs at 80 K are approximately an order of magnitude longer than those at RT [14, 19, 28].”

In the citing paper

“At 80 K, our measurements align closely with first-principles results, calculated through interpolation of calculations by Minnich et al. at 100 K and 60 K [14], with a slight deviation for phonons with short MFPs.”

In the citing paper

“These findings are consistent with the conclusion that the ballistic thermal resistance effects found in TDTR measurements in both this and previous [39] works can contribute over a wide temperature range extending from cryogenic up to even room temperatures.”

In the citing paper

“This interpretation is the same as that of Koh and Cahill 16 , and consistent with Minnich et al. 1 and Johnson et al. 19,20 who instead used the laser spot diameter and transient grating period as the cutoff dimensions.”

In the citing paper

“Although our data compare favourably with the first principles predictions by Esfarjani and coworkers 1,2,41 at all temperatures”

In the citing paper

“The diameter dependence of the radial heat flux demonstrates that the pump size is a key variable that sets the thermal length scale for radial transport, confirming previous explanations for observations of a pump-beam size dependent thermal conductivity.14”

In the citing paper

“The results show the experimentally observed trend of decreasing effective thermal conductivity with decreasing pump beam size.14”

In the citing paper

“At these temperatures, our result predicts a similar trend in thermal conductivity versus pump size”

In the citing paper

“Recent studies have shown that it is possible to experimentally measure the MFP dependent contributions of phonons to thermal conductivity–the phonon MFP spectrum12345.”

In the citing paper

“Further studies using TDTR have equated l* to the laser spot size on Si3 and the dimensions of nano-patterned heaters on sapphire26.”

In the citing paper

“Heat sources with dimensions smaller than phonon MFPs also perceive a locally suppressed thermal conductivity323.”

In the citing paper

“However, care should be taken when applying a diffusive thermal transport model to systems where a significant fraction of heat is carried by phonons with long mean-free paths (MFPs). 90-92, 112”

In the citing paper

“Furthermore, the thermal conductivity reductions reported by Minnich et al. [39] for comparable pump diameters in natural silicon agree in trend over the reported temperature range, as shown in Fig. 7.”

In the citing paper

“This is consistent with the results of Minnich et al. whose measurements were independent of modulation frequency (i.e., varying thermal penetration depth), but instead showed a pump diameter dependence.”