Transport and noise spectroscopy of MWCNT/HDPE composites with different nanotube concentrations

Electrical current transport and low-frequency noise spectra of multiwall carbon nanotubes in high-density polyethylene matrix have been measured in a temperature range between 10 and 300 K. The dc electrical investigations suggest that these composites can be regarded as a random resistor network, where the resistors are formed by tunnel junctions between carbon nanotubes. A crossover of the conduction from a low-field to a high-field regime is found in current-voltage characteristics. In particular, the high-field regime has a strong dependence on carbon nanotube concentration. Noise measurements reveal a standard 1/f behavior due to resistance fluctuations. However, in samples with different concentration of nanotubes, an unusual temperature dependence of the noise is observed. The samples with higher percentage of nanotubes seem to be the most promising ones for devices application, since their noise level is lower in the whole investigated temperature range.