Poole-Frenkel conduction in single wall carbon nanotube composite films built up by electrostatic layer-by-layer deposition

The fabrication of large area thin films of single wall carbon nanotubes (SWCNTs) using electrostatic layer-by-layer deposition is reported. The in-plane current versus voltage (I-V) characteristics were dependent on the concentration of SWCNTs transferred from the solvents onto the substrates. Solutions with a low SWCNT concentration produced films that exhibited a nonlinear I-V regime. The experimental data fitted with various conduction models indicated that Poole-Frenkel conduction was the dominant mechanism. The temperature dependence of the conductivity also supported this model. Two activation energies were identified-approximately 10 and 20 meV. These were thought to be associated with the surfactant coatings of the nanotubes. Increasing the SWCNT loading in the thin films led to an Ohmic conduction process by virtue of a denser network of conductive paths in the film and conduction via tube to tube contacts.