The effect of structure on the low-temperature electrical conductivity of carbon nanocomposite temperature sensors

Abstract

The electrical conductivity of carbon nanocomposite TVO-series resistors used as temperature sensors are studied in a wide temperature range of 300–1.8 K. It is found that hopping conductivity emerges at temperatures below 77 K. The shape of its temperature dependence varies for resistors having different resistance at room temperature. Raman spectra measurements have shown that the resistors differ according to the size of the carbon nanoparticles in the composite material of the conducting region and its dispersion along the direction of the current. The measured dependences of conductivity on temperature and magnitude of the applied electric field, wherein the charge carriers are heated by the field, are used to determine charge carrier localization lengths, which are almost two orders of magnitude greater than the carbon nanoparticles. The observed features of the conductivity can be explained by a nonuniform distribution of carbon in the composite material and the formation of nanoparticle clusters with quasi-metallic conductivity, while the conductivity between the clusters occurs due to carrier hopping.