Single-walled carbon nanotubes (SWNTs), prepared by metal-catalysed laser ablation of graphite, form close-packed bundles or 'ropes'. These rope crystallites exhibit metallic behaviour above 50 K (ref. 2), and individual tubes behave as molecular wires, exhibiting quantum effects at low temperatures. They offer an all-carbon host lattice that, by analogy with graphite and solid C60 (ref. 6), might form intercalation compounds with interesting electronic properties, such as enhanced electrical conductivity and superconductivity. Multi-walled nanotube materials have been doped with alkali metals and FeCl3 (ref. 8). Here we report the doping of bulk samples of SWNTs by vapour-phase reactions with bromine and potassium - a prototypical electron acceptor and donor respectively. Doping decreases the resistivity at 300 K by up to a factor of 30, and enlarges the region where the temperature coefficient of resistance is positive (the signature of metallic behaviour). These results suggest that doped SWNTs represent a new family of synthetic metals.
CITATION STYLE
Lee, R. S., Kim, H. J., Fischer, J. E., Thess, A., & Smalley, R. E. (1997). Conductivity enhancement in single-walled carbon nanotube bundles doped with K and Br. Nature, 388(6639), 255–257. https://doi.org/10.1038/40822
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