Reducing electrical resistance in single-walled carbon nanotube networks: effect of the location of metal contacts and low-temperature annealing

The ability to control the density of single-walled carbon nanotubes (SWNTs) during the formation of 2D networks allows one to tune the electrical properties of these thin-films from semiconductive to metallic conduction, allowing their use in numerous new materials applications. However, the resistances of such thin-films are generally non-optimal, dominated by the effects of inter-SWNT tunneling junctions, metal/SWNT contacts, sidewall defects, and the presence of residual dopants. These studies provide insight into the relative contributions of these various items to the overall resistance of an SWNT network contacted by Ti electrodes, and ways to reduce these effects via changing the structure of the metal/SWNT contact, and annealing at low temperature. Further, the addition of a mild-acid treatment was found to cause a 13-fold reduction in resistance and much greater reproducibility in inter-network conductivity.