Thermal Conductivity Spectroscopy Technique to Measure Phonon Mean Free Paths
01 Aug 2011-
TL;DR: In this paper, the authors proposed a new approach for energy efficiency in renewable energy systems, which is supported by the U.S. Dept. of Energy (DE-SC0001299/DE-FG02-09ER46577).
Abstract: United States. Dept. of Energy. Office of Basic Energy Sciences (Grant No. DE-SC0001299/DE-FG02-09ER46577)
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University of Illinois at Urbana–Champaign1, Massachusetts Institute of Technology2, Harvard University3, Stanford University4, Rensselaer Polytechnic Institute5, Pennsylvania State University6, University of California, Berkeley7, Brown University8, University of Florida9, University of Texas at Austin10
TL;DR: In this article, a review of thermal transport at the nanoscale is presented, emphasizing developments in experiment, theory, and computation in the past ten years and summarizes the present status of the field.
Abstract: A diverse spectrum of technology drivers such as improved thermal barriers, higher efficiency thermoelectric energy conversion, phase-change memory, heat-assisted magnetic recording, thermal management of nanoscale electronics, and nanoparticles for thermal medical therapies are motivating studies of the applied physics of thermal transport at the nanoscale. This review emphasizes developments in experiment, theory, and computation in the past ten years and summarizes the present status of the field. Interfaces become increasingly important on small length scales. Research during the past decade has extended studies of interfaces between simple metals and inorganic crystals to interfaces with molecular materials and liquids with systematic control of interface chemistry and physics. At separations on the order of ∼1 nm, the science of radiative transport through nanoscale gaps overlaps with thermal conduction by the coupling of electronic and vibrational excitations across weakly bonded or rough interface...
1,307 citations
01 Jan 2012
TL;DR: In this article, Minnich et al. reviewed the progress made in thermoelectrics over the past two years on charge and heat carrier transport, strategies to improve the thermiolectric figure of merit, with new discussions on device physics and applications.
Abstract: This review is an update of a previous review (A. J. Minnich, et al., Energy Environ. Sci., 2009, 2, 466) published two years ago by some of the co-authors, focusing on progress made in thermoelectrics over the past two years on charge and heat carrier transport, strategies to improve the thermoelectric figure of merit, with new discussions on device physics and applications, and assessing challenges on these topics. Understanding of phonon transport in bulk materials has advanced significantly as the first-principles calculations are applied to thermoelectric materials, and experimental tools are being developed. Some new strategies have been developed to improve electron transport in thermoelectric materials. Fundamental questions on phonon and electron transport across interfaces and in thermoelectric materials remain. With thermoelectric materials reaching high ZT values well above one, the field is ready to take a step forward and go beyond the materials' figure of merit. Developing device contacts and module fabrication techniques, developing a platform for efficiency measurements, and identifying applications are becoming increasingly important for the future of thermoelectrics.
826 citations
TL;DR: A breakdown in diffusive phonon transport generated by high-frequency surface temperature modulation is used to identify the mean free path-dependent contributions of phonons to thermal conductivity in crystalline and amorphous silicon.
Abstract: Little is known about the mean free path spectra of lattice vibrations—known as phonons—that carry heat in non-metallic solids. Regner et al . demonstrate a technique that enables measurement of these spectra over an unprecedented range, enabling a more complete pi…
519 citations
TL;DR: In this article, the authors discuss some of the challenges that must be overcome to enable widespread use of thermoelectric power generation (TEG) devices, including thermal stability at the material level, and reliable contact at the device level.
426 citations
TL;DR: This work experimentally measures the intrinsic spectral distribution of energy among heat carriers by probing quasi-ballistic transport near nanostructured heaters down to 30 nm using ultrafast optical spectroscopy, providing a new fundamental understanding of thermal transport.
Abstract: Controlling thermal properties is central to many applications, such as thermoelectric energy conversion and the thermal management of integrated circuits. Progress has been made over the past decade by structuring materials at different length scales, but a clear relationship between structure size and thermal properties remains to be established. The main challenge comes from the unknown intrinsic spectral distribution of energy among heat carriers. Here, we experimentally measure this spectral distribution by probing quasi-ballistic transport near nanostructured heaters down to 30 nm using ultrafast optical spectroscopy. Our approach allows us to quantify up to 95% of the total spectral contribution to thermal conductivity from all phonon modes. The measurement agrees well with multiscale and first-principles-based simulations. We further demonstrate the direct construction of mean free path distributions. Our results provide a new fundamental understanding of thermal transport and will enable materials design in a rational way to achieve high performance.
301 citations