Dedoping of Carbon Nanotube Networks Containing Metallic Clusters and Chloride

Doping carbon nanotube films improves their electrical conductivity and chemical stability. One conventional doping method is the in situ reduction of AuCl₃ and yet its beneficial properties on the electrical conductivity lessen once the films are thermally annealed. Here, density functional theory and semiclassical Boltzmann transport theory calculations show a deterioration of the electrical conductivity of a doped network of (8,0) carbon nanotubes as the Au_n clusters (n ≤ 10) become larger or the Cl impurity concentration decreases. Between the smallest and largest cluster sizes, the conductivity along the nanotubes and across the junction dropped by 47 and 90% in metallic networks. The declines in semiconducting networks were 50 and 13%, respectively. The maximum electrical conductivity across the junction was for networks containing Au₅ clusters (193 times larger than the pristine network). Additionally, the electrical transport was reduced when Cl impurities were removed. Networks with excess Cl impurities had 9.6 and 36.7 times larger electrical conductivity along the nanotubes and across the junction than networks without impurities. Controlling the cluster size and Cl content would mitigate the dedoping of carbon nanotube films after thermal annealing.