Direct Visualization of Thermal Conductivity Suppression Due to Enhanced Phonon Scattering Near Individual Grain Boundaries
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2018-04-09 |
| Journal | Nano Letters |
| Authors | Aditya Sood, Ramez Cheaito, Tingyu Bai, Heungdong Kwon, Yekan Wang |
| Institutions | University of California, Los Angeles, Georgia Institute of Technology |
| Citations | 125 |
Abstract
Section titled âAbstractâUnderstanding the impact of lattice imperfections on nanoscale thermal transport is crucial for diverse applications ranging from thermal management to energy conversion. Grain boundaries (GBs) are ubiquitous defects in polycrystalline materials, which scatter phonons and reduce thermal conductivity (Îș). Historically, their impact on heat conduction has been studied indirectly through spatially averaged measurements, that provide little information about phonon transport near a single GB. Here, using spatially resolved time-domain thermoreflectance (TDTR) measurements in combination with electron backscatter diffraction (EBSD), we make localized measurements of Îș within few ÎŒm of individual GBs in boron-doped polycrystalline diamond. We observe strongly suppressed thermal transport near GBs, a reduction in Îș from âŒ1000 W m<sup>-1</sup> K<sup>-1</sup> at the center of large grains to âŒ400 W m<sup>-1</sup> K<sup>-1</sup> in the immediate vicinity of GBs. Furthermore, we show that this reduction in Îș is measured up to âŒ10 ÎŒm away from a GB. A theoretical model is proposed that captures the local reduction in phonon mean-free-paths due to strongly diffuse phonon scattering at the disordered grain boundaries. Our results provide a new framework for understanding phonon-defect interactions in nanomaterials, with implications for the use of high-Îș polycrystalline materials as heat sinks in electronics thermal management.