Resistance–temperature dependence in carbon nanotube fibres

Low temperature electrical transport in modified carbon nanotube fibres

“…We have recently shown that in-depth analysis of R-T 50 curves may aid an assessment of the influence of the exact morphology of the fibres, determined during the production process, on their electrical transport, and thus the usefulness of the employed process [9]. Here we show that a similar method may be used to provide insight into the changes of transport in CNT fibres due to their modification by foreign molecules.…”

“…for more semiconducting materials. The above model supplemented with an exponential term, for scattering in quasi 1D metals 1 b  exp(Àd/T), where b and d are fitting parameters, allows fitting of R-T curves in the whole range of temperatures and facilitates comparison between samples [9,15,16]. The latter term although it provides values consistent with the previous literature, will not be considered in detail here, as its rigorous derivation still needs further study [9,17].…”

“…The R-T characteristics may change gradually from very metallic to semiconducting depending on the morphology of the fibres and foreign inclusions. To provide extreme 40 examples, highly pure fibres made of armchair CNTs or fibres heavily doped with acids may show a decrease in resistance down to 40-50 K, and only below this crossover temperature show a weak semiconductor-like increase in resistance towards 0 K [4,5,9]. On the other hand, poor quality fibres or fibres composited with non-conductive polymers may show an insignificant contribution of metallic type behaviour and, above room temperature, a crossover to a steep semiconducting slope [9][10][11][12].…”

“…To provide extreme 40 examples, highly pure fibres made of armchair CNTs or fibres heavily doped with acids may show a decrease in resistance down to 40-50 K, and only below this crossover temperature show a weak semiconductor-like increase in resistance towards 0 K [4,5,9]. On the other hand, poor quality fibres or fibres composited with non-conductive polymers may show an insignificant contribution of metallic type behaviour and, above room temperature, a crossover to a steep semiconducting slope [9][10][11][12].We have recently shown that in-depth analysis of R-T 50 curves may aid an assessment of the influence of the exact morphology of the fibres, determined during the production process, on their electrical transport, and thus the usefulness of the employed process [9]. Here we show that a similar method may be used to provide insight into the changes of transport in CNT fibres due to their modification by foreign molecules.…”

“…To allow quantitative analysis of the changes in R-T curves mentioned in the introduction we have developed a new theoretical model [9]. The main formula Eq.…”