Temperature-dependent transport and 1/f noise mechanisms in single-walled carbon nanotube films

The temperature dependence of 1/f noise and resistivity in single-walled carbon nanotube (CNT) films are studied. We find that as the temperature decreases, resistivity monotonically increases whereas 1/f noise amplitude first decreases, then increases, reaching a minimum at around 40 K. At temperatures considerably smaller than 40 K, the temperature dependence of both resistivity and 1/f noise amplitude can be explained by three-dimensional Mott variable-range hopping, which is due to localization effects that result in an insulating behavior in CNT films. At higher temperatures, on the other hand, the dependence of resistivity on temperature can be explained by fluctuation-induced tunneling. In this high-temperature regime, we analyze the temperature dependence of the noise amplitude to extract the density of fluctuators as a function of their energy. Our results show a characteristic peak between 0.3 and 0.6 eV that is responsible for the majority of 1/f noise. We also find that, due to its correlation with the number of carriers, the noise amplitude is very sensitive to CNT film device dimensions, especially near the percolation threshold where the resistivity increases. These results not only provide fundamental physical insights about transport and 1/f noise mechanisms in CNT films at different temperatures but also help assess the suitability of these films for device applications.