Thermal Conductance of an Individual Single-Wall Carbon #47 TSUN

Thermal Conductance of an Individual Single-Wall Carbon #47 TSUN

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Thermal Conductance of an Individual Single-Wall Carbon Nanotube above Room Temperature Eric Pop, ²,‡ David Mann, ² Qian Wang, ² Kenneth Goodson, and Hongjie Dai* Department of Chemistry and Laboratory for Ad V anced Materials, and Department of Mechanical Engineering and Thermal Sciences, Stanford Uni V ersity, Stanford, California 94305 Received October 31, 2005 ABSTRACT The thermal properties of a suspended metallic single-wall carbon nanotube (SWNT) are extracted from its high-bias ( I - V ) electrical characteristics over the 300 - 800 K temperature range, achieved by Joule self-heating. The thermal conductance is approximately 2.4 nW/K, and the thermal conductivity is nearly 3500 Wm - 1 K - 1 at room temperature for a SWNT of length 2.6 μ m and diameter 1.7 nm. A subtle decrease in thermal conductivity steeper than 1/ T is observed at the upper end of the temperature range, which is attributed to second-order three-phonon scattering between two acoustic modes and one optical mode. We discuss sources of uncertainty and propose a simple analytical model for the SWNT thermal conductivity including length and temperature dependence. Single-wall carbon nanotubes (SWNTs) have sparked great scientific and engineering interest because of their outstand- ing electrical and thermal properties. Consequently, they have been proposed for applications in integrated circuits (as transistors or interconnects) 1 - 3 and in thermal management (as thermal interface materials). 4 In both cases, knowledge of their thermal properties is key to understanding their overall behavior. 5 Although several theoretical studies exist on the thermal conductivity of individual SWNTs, 6 - 11 only few experimental estimates are currently available, 12 and no investigations exist above room temperature. However, it is this temperature range that is expected to be of most practical importance for applications of carbon nanotubes in electron- ics and integrated circuits. In this Letter we extract the thermal conductance of an individually suspended SWNT in the 300 - 800 K tempera- ture range. For the first time, we empirically find a subtle decrease in the thermal conductivity of the SWNT near the upper end of this temperature range, which is proportional to 1/ T 2 because of second-order three-phonon scattering processes. The approach presented employs direct (DC) self- heating of the nanotube under high-bias current flow in several ambient temperatures (from 250 to 400 K). This method relies on the direct relationship between the SWNT lattice temperature and phonon-limited electrical transport and may be generally applicable to other one-dimensional systems where similar transport conditions occur at high electrical bias (e.g., nanowires or other molecular wires). Suspended SWNTs were grown across Pt contacts and
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Thermal Conductance of an Individual Single-Wall Carbon #47 TSUN

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