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Pettes in the lab with a cryostat and equipment used for electrical, thermal, and thermoelectric measurements of nanostructured materials.

Pettes in the lab with a cryostat and equipment used for electrical, thermal, and thermoelectric measurements of nanostructured materials.

Michael T. Pettes and Associate Professor Li Shi were honored with a Best Poster Award for their work entitled “Thermal and Structural Characterizations of Individual Carbon Nanotubes” during the 2009 Fall Meeting of the Materials Research Society held in Boston, MA on December 3, 2009. The results are also highlighted as a frontispiece article in the journal Advanced Functional Materials.

The quest for computer chip technology and materials to improve heat dissipation

As silicon-based transistor technology continues to scale ever downward, anticipation of the fundamental limitations of ultimately-scaled devices has prompted research into alternative device technologies as well as new materials for interconnects and packaging. Low dimensional carbon nanomaterials, such as 1D carbon nanotubes (CNTs), have received interest for both electronic device and thermal management application solutions.

Cryostat sample holder showing the suspended microthermometer device used for thermal conductance measurements of individual carbon nanotubes.

Cryostat sample holder showing the suspended microthermometer device used for thermal conductance measurements of individual carbon nanotubes.

Carbon nanotubes

In CNTs, high axial thermal conductivity and electron mobility is expected for defect-free nanotubes, as long-range crystallinity along the axial direction and negligible boundary scattering in unconstrained nanotubes allow heat and charge carriers to flow with greater ease than in traditional semiconductor materials. The thermal conductivity of CNTs is potentially comparable to or higher than that for diamond and graphite (in-plane), which display the highest measured thermal conductivity of any known bulk materials. Additionally, as power dissipation becomes an increasingly important challenge in highly miniaturized electronic devices, their high thermal conductivity makes CNTs attractive for heat dissipation solutions such as thermal interface materials (TIMs). However, owing to variations in structure defect concentration and thermal contact resistance that were not adequately characterized in several prior measurements, a wide range of thermal conductivity values have been reported.

Research goals

The goal of the presented research is to demonstrate a capability for establishing the structure-thermal property relationship of different types of individual CNTs using a suspended microthermometer device to allow for a fundamental understanding of thermal transport processes in these materials.

Supporters

This work is supported by the U.S. Department of Energy and the Thermal Transport Processes Program and Graduate Research Fellowship Program of the National Science Foundation.


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