Effects of adsorption of alcohol and water on the electrical transport of carbon nanotube bundles

In situ studies on the effects of physisorption of various alcohol molecules (CnH2n+1OH; n = l-4) on the transport properties of thin films of bundled single-walled carbon nanotubes reveal large increases in the thermoelectric power (TEP) S (~l-4 *mV K-1) and four-probe resistance R (~4-8%) at 40 de...

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Veröffentlicht in:Journal of physics. Condensed matter 2004-03, Vol.16 (12), p.1939-1949
Hauptverfasser: Romero, H E, Sumanasekera, G U, Kishore, S, Eklund, P C
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Sprache:eng
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Zusammenfassung:In situ studies on the effects of physisorption of various alcohol molecules (CnH2n+1OH; n = l-4) on the transport properties of thin films of bundled single-walled carbon nanotubes reveal large increases in the thermoelectric power (TEP) S (~l-4 *mV K-1) and four-probe resistance R (~4-8%) at 40 deg C. Interestingly, exposure to water causes virtually no change in the TEP, although the electrical resistance shows a change of ~4%, typical for the alcohols. We observe a simple exponential response of S (t) and R (t) to a sudden change in the molecular pressure. The characteristic time constants (*t ~ 10 min) for S and R are found to be essentially the same for a given molecule, indicating that the changes in these transport properties track each other. In fact, plots of S versus *DR are linear, the slopes depending on the specific molecule. The transport results are interpreted in terms of a Boltzmann model and the introduction of a new scattering channel for charge carriers in metallic tubes due to weak interactions with physisorbed molecules. The trends in the changes in S and R with adsorption of these polar molecules can be explained on the basis of the interplay between the adsorption energy and the molecular coverage on the nanotube surfaces.
ISSN:0953-8984
1361-648X
DOI:10.1088/0953-8984/16/12/004