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 Aun 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.