Experimental observation of scaling laws for alternating current and direct 
current conductivity in polymer-carbon nanotube composite thin films

Kilbride, B. E.; Coleman, J. N.; Fraysse, J.; Fournet, P.; Cadek, M.; Drury, A.; Hutzler, S.; Roth, S.; Blau, W. J.

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Experimental observation of scaling laws for alternating current and direct current conductivity in polymer-carbon nanotube composite thin films

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Fraysse, J.
Abteilung v. Klitzing, Former Departments, Max Planck Institute for Solid State Research, Max Planck Society;

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Roth, S.
Abteilung v. Klitzing, Former Departments, Max Planck Institute for Solid State Research, Max Planck Society;

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Citation

Kilbride, B. E., Coleman, J. N., Fraysse, J., Fournet, P., Cadek, M., Drury, A., et al. (2002). Experimental observation of scaling laws for alternating current and direct current conductivity in polymer-carbon nanotube composite thin films. Journal of Applied Physics, 92(7), 4024-4030.

Cite as: https://hdl.handle.net/21.11116/0000-000E-E41D-1

Abstract

Alternating current (ac) and direct current (dc) conductivities
have been measured in polymer-nanotube composite thin films.
This was carried out for a range of concentrations of multiwall
nanotubes in two polymer hosts, poly(m-phenylenevinylene-co-
2,5-dioctyloxyp-phenylenevinylene) (PmPV) and polyvinylalcohol
(PVA). In all cases the dc conductivity sigma(DC) was ohmic in
the voltage range studied. In general the ac conductivity
displayed two distinct regions, a frequency independent region
of magnitude sigma(0) at low frequency and a frequency
dependent region at higher frequency. Both sigma(DC) and
sigma(0) followed a percolation scaling law of the form
sigmaproportional to(p-p(c))(t) with p(c)=0.055% by mass and
t=1.36. This extrapolates to a conductivity of 1x10(-3) S/m for
100% nanotube content. Such a low value reflects the presence
of a thick polymer coating, resulting in poor electrical
connection between tubes. This leads to the suggestion that
charge transport is controlled by fluctuation induced
tunneling. In the high frequency regime the conductivity
increases with frequency according to an approximate power law
with exponent sapproximate to0.92, indicative of hopping
transport. The onset of this frequency independent conductivity
scales with mass fraction for the PmPV composite due to the
variation of correlation length with nanotube content. This
behavior is discussed in terms of a biased random walk in three
dimensions. In addition ac universality is demonstrated by the
construction of a mastercurve. (C) 2002 American Institute of
Physics.