Electronic Transport Properties of Carbon-Nanotube Networks: The Effect of Nitrate Doping on Intratube and Intertube Conductances

Abstract

The conductivity of carbon-nanotube (CNT) networks can be improved markedly by doping with nitric acid. In the present work, CNTs and junctions of CNTs functionalized with NO 3 molecules are investigated to understand the microscopic mechanism of nitric acid doping. According to our density-functional-theory band-structure calculations, there is charge transfer from the CNT to adsorbed molecules indicating p-type doping. The average doping efficiency of the NO 3 molecules is higher if the NO 3 molecules form complexes with water molecules. In addition to electron transport along individual CNTs, we also study electron transport between different types (metallic, semiconducting) of CNTs. Reflecting the differences in the electronic structures of semiconducting and metallic CNTs, we find that in addition to turning semiconducting CNTs metallic, doping further increases electron transport most efficiently along semiconducting CNTs as well as through the junctions between them.

Bridging the Junction: Electrical Conductivity of Carbon Nanotube Networks

“…The local conductivity minima occur when the bands are flat such as at −0.5 and −1.5 eV. These are Van Hove singularities, which have local maxima in the density of states and have previously been noted for CNT systems …”

“…However, standard percolation theory lacks the electronic structure information of the nanotubes. Computational studies based on density-functional theory (DFT) have revealed how the overall conductivity and electronic structure of a CNT network are changed by analytes or dopants such as H 2 , nitrogen oxides, , gold chlorides, , halogens, and transition metals . DFT methods predict significant variation in the electronic transport and reactivity of different configurations of N-substituted nanotubes. − Enhanced conductivity and improved sheet resistance have been measured experimentally in films containing Cl anions or doped with Cr .…”

Optoelectronic and charge transport properties of the complex of carbon nanotube with perylene bisimide

“…In one of our studies, it was observed that the complexes of indigo wrapped over CNT exhibit p‐type charge transfer characteristics . Very recently, Ketolainen et al examined the adsorption of nitrates on the surface of CNT and found a p‐type characteristics owing to the charge transfer from donor CNT to acceptor nitrates . On the other hand, Koizhaiganova and coworkers reported n‐type charge‐transfer characteristics for the complexes of CNT with aromatic amines wherein CNT acts as an acceptor for the donor amines .…”

Overcoming the Sticking Point: Electrical Conductivity of Carbon Nanotube Networks Containing 3d Metals

“…Intense Raman peaks have been observed from nanotubes with encapsulated S . The adsorption of H 2 was more favorable on transition-metal-decorated CNTs than pristine CNTs. − NO 3 , AuCl 3 , AuCl 4 , or halogens induce p-type behavior in semiconducting CNT networks. − Atomic gold clusters at the CNT intersection increase the electrical conductivity if the clusters have an odd number of atoms …”