Effect of concentration on low-frequency noise of multiwall carbon nanotubes in high-density polyethylene matrix

Transport and noise measurements of multiwall carbon nanotubes in high-density polyethylene matrix are reported. In these composites current transport occurs through a random tunnel junctions network, formed by adjacent carbon nanotubes. Low-frequency noise investigations reveal a 1/f behavior induced by resistance fluctuations. An unusual temperature dependence in samples with different nanotube concentration is found. This can be explained by a transition from a fluctuation-induced tunneling mechanism to a thermally activated regime, occurring at increasing nanotube concentration and resulting in a decrease in the overall noise.