Thermal Transport Measurements of Individual Multiwalled Nanotubes #46 TSUN

Thermal Transport Measurements of Individual Multiwalled Nanotubes #46 TSUN

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VOLUME 87, NUMBER21 PHYSICAL REVIEW LETTERS 19N OVEMBER 2001 Thermal Transport Measurements of Individual Multiwalled Nanotubes P. Kim, 1 L. Shi, 2 A. Majumdar, 2 and P. L. McEuen 1,3, * 1 Department of Physics, University of California, Berkeley, California 94720 2 Department of Mechanical Engineering, University of California, Berkeley, California 94720 3 Division of Materials Sciences, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (Received 1 June 2001; published 31 October 2001) The thermal conductivity and thermoelectric power of a single carbon nanotube were measured using a microfabricated suspended device. The observed thermal conductivity is more than 3000 W y K m at room temperature, which is 2 orders of magnitude higher than the estimation from previous experiments that used macroscopic mat samples. The temperature dependence of the thermal conductivity of nanotubes ex- hibits a peak at 320 K due to the onset of umklapp phonon scattering. The measured thermoelectric power shows linear temperature dependence with a value of 80 m V y K at room temperature. DOI: 10.1103/PhysRevLett.87.215502 PACS numbers: 61.46.+w, 63.22.+m, 65.80.+n The thermal properties of carbon nanotubes are of fun- damental interest and also play a critical role in controlling the performance and stability of nanotube devices [1]. Un- like electrical and mechanical properties, which have been studied at a single nanotube level [2], the thermal prop- erties of carbon nanotubes have not been measured at a mesoscopic scale. The speciFc heat, thermal conductivity, and thermoelectric power (TEP) of millimeter-sized mats of carbon nanotubes have been measured by several groups [3–13]. Although these studies have yielded a qualitative understanding of the thermal properties of these materials, there are signiFcant disadvantages to these “bulk” mea- surements for understanding intrinsic thermal properties of a single nanotube. One problem is that these measure- ments yield an ensemble average over the different tubes in a sample. More importantly, in thermal transport mea- surements such as thermal conductivity and TEP, it is dif- Fcult to extract absolute values for these quantities due to the presence of numerous tube-tube junctions. These junc- tions are in fact the dominant barriers to thermal transport in a mat of nanotubes. In this Letter, we present the results of mesoscopic ther- mal transport measurements of individual carbon nano- tubes. We have developed a microfabricated suspended device hybridized with multiwalled nanotubes (MWNTs) to probe thermal transport free from a substrate contact. The observed thermal conductivity of a MWNT is 2 or- ders of magnitude higher than the value found in previous bulk measurements and is comparable to the theoretical expectations. Suspended structures were fabricated on a silicon nitride/silicon oxide/silicon multilayer by electron beam and photolithography followed by metallizations and etching processes, which are described elsewhere in detail [14]. ±igure 1(a) shows a representative device including two 10 m m 3 10 m
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Thermal Transport Measurements of Individual Multiwalled Nanotubes #46 TSUN

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