Electronic transport properties of conducting polymers and carbon nanotubes

Kaiser, A. B.

doi:10.1088/0034-4885/64/1/201

Cited by 408 publications

(363 citation statements)

References 179 publications

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“…3b, indicate that the overall conductance is limited by hopping conduction through disordered regions. The approximate linearity of the plot of log(G) vs. T 1/2 agrees with the variable-range hopping conductivity expression [20,21] …”

Section: Thin Transparent Swnt Filmssupporting

confidence: 78%

Ion irradiation effects on conduction in single-wall carbon nanotube networks

et al. 2008

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We have measured how irradiation by Ar + and N + ions modifies electronic conduction in single-wall carbon nanotube (SWNT) networks, finding dramatically different effects for different thicknesses. For very thin transparent networks, ion irradiation increases localization of charge carriers and reduces the variable-range hopping conductivity, especially at low temperatures. However, for thick networks (SWNT paper) showing metallic conductivity, we find a relatively sharp peak in conductivity as a function of irradiation dose. Our investigation of this peak reveals the important role of thermal annealing extending beyond the range of the irradiating ions, and shows the dependence on the morphology of the samples. We propose a simple model that accounts for the temperature-dependent conductivity. Recently, the effect of defects on the conducting properties of individual metallic single-wall carbon nanotubes (SWNTs) was shown [1,2] by the controlled reduction of the electronic localization length by irradiation with Ar + ions. For these SWNTs in the strong Anderson localization regime, the exponential increase of resistance with length of SWNTs between electrodes was greatly enhanced by di-vacancies created by the Ar + ions. In this paper, we report the first measurements (to our knowledge) of the effect of irradiation by ions on conduction in thin transparent SWNT networks, finding that resistance always increases on ion irradiation. In contrast to these results, however, we show that ion irradiation initially decreases the resistance of our thick SWNT networks.Many applications proposed for carbon nanotubes [3][4][5][6] are likely to be sensitive to irradiation effects, which u Fax: +49-711-689-1010, E-mail: v.skakalova@fkf.mpg.de would be particularly significant, for example, for devices used in space or other high-radiation environments. Controlled irradiation also has many applications related to carbon nanotubes. It has been demonstrated by experimental and theoretical studies that irradiation can be used for nano-engineering of carbon nanotubes [7,8]. For example, focused electron beams were shown to result in welding of crossed single-wall carbon nanotubes to form molecular junctions [9], and molecular dynamics simulations showed how such junctions might also be produced by irradiation by Ar + ions [10]. Irradiation by 1.25-MeV electrons at high temperature (800 • C) was able to coalesce neighbouring Ndoped SWNTs as a result of defect formation followed by thermal annealing [11]. Using irradiation by Ar + ions, Stahl et al. [12] introduced defects in the SWNTs in the upper part of a bundle of loosely coupled SWNTs before depositing gold contacts on top of the bundle. They found that to avoid the defects, the current switched to undamaged nanotubes in the lower part of the bundle, tunnelling being the transfer mechanism between nanotubes.In previous work [13], we observed local modifications of the electronic structure in atomically resolved scanning tunnelling microscope (STM) images of multi-wal...

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Section: Thin Transparent Swnt Filmssupporting

confidence: 78%

Ion irradiation effects on conduction in single-wall carbon nanotube networks

et al. 2008

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“…5 for the same temperature interval. In spite of the small number and dispersion of the data points, one may notice that in the crystalline regions the temperature behavior resembles the 1D conductivity 24 in agreement with Ref. 11.…”

Section: ͑1͒supporting

confidence: 87%

Simultaneous observation of the magnetic and electric behavior in a correlated system near a metal-semiconductor transition: ESR in pellets of conducting polymers

et al. 2009

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Electron spin resonance ͑ESR͒ experiments show, at the metal-semiconductor transition temperature of a conducting polymer, the distinct contributions of the disordered and crystalline regions. In the more disordered regions of the polymer the polarons experience an antiferromagnetic coupling. As the level of disorder decreases, when small crystalline regions appear, there is a tendency, in some temperature range, for the polarons to interact ferromagnetically. For more ordered regions or crystalline regions of larger sizes, there is a competition between localized ferromagnetic coupled polarons and delocalized ones, that is, between localization and delocalization. The possibility to fit the ESR data for one of the samples using two Dysonian lines, one for each phase, allows one to follow the general behavior of the microwave conductivity as a function of the temperature. The semiconducting behavior of the disordered phase is clearly observed, as well as the true metallic behavior of the crystalline phase revealed by the increase in conductivity with the decrease in temperature.

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“…This is especially true at low temperatures where the metallic sign of the temperature dependence is suppressed and the resistance decreases as temperature increases. The disordered regions, however, provide less of a barrier to thermal conduction, and so typically thermopower shows metallic temperature dependence to lower temperatures than resistivity [5].…”

Section: Thermopower and Implications For Superconductivitymentioning

confidence: 99%

“…One such feature is the mixture of metallic and non-metallic character seen even for highly conducting samples. A heterogenous conduction model is able to account for the change from nonmetallic to metallic temperature dependence as temperature increases in highly conducting polymers, and also for the fact that thermopower remains metallic in character down to low temperatures [4,5]. The origin of this heterogeneity is the incomplete crystallinity of the polymers, which gives rise to disordered regions around the small crystallites [6].…”

Section: Introductionmentioning

confidence: 99%

Charge Transport in Conducting Polymers: Polyacetylene Nanofibres

Kaiser

Rogers

Park

2004

Molecular Crystals and Liquid Crystals

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The preparation of individual polyacetylene nanofibres has allowed a more probing investigation of the properties of polyacetylene. A significant discovery is that at low temperatures, polyacetylene nanofibres show temperature-independent Zener-type tunnelling, that we suggest is tunnelling of the conjugated-bond pattern along single polyacetylene chains. At higher temperatures, the current shows a strong increase with temperature and the nonlinearity of the current-voltage characteristics decreases. We make a comparison with similar behaviour found in single-wall carbon nanotube networks, and show that the decrease in nonlinearity is consistent with our generic calculations for fluctuation-assisted tunnelling and thermal excitation. There is no evidence for superconductivity in resistance measurements on polyacetylene. The thermoelectric power of polyacetylene and other bulk organic conducting polymers indicates the absence of significant superconductivity arising from the conventional electron-phonon mechanism.

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Electronic transport properties of conducting polymers and carbon nanotubes

Cited by 408 publications

References 179 publications

Ion irradiation effects on conduction in single-wall carbon nanotube networks

Ion irradiation effects on conduction in single-wall carbon nanotube networks

Simultaneous observation of the magnetic and electric behavior in a correlated system near a metal-semiconductor transition: ESR in pellets of conducting polymers

Charge Transport in Conducting Polymers: Polyacetylene Nanofibres

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