Nitrogen-Doped Single-Walled Carbon Nanotube Thin Films Exhibiting Anomalous Sheet Resistances

Nitrogen-doped single-walled carbon nanotubes (N-SWCNTs) were synthesized using a floating catalyst aerosol chemical vapor deposition method, with carbon monoxide as the carbon source, ammonia as the nitrogen source, and iron particles derived from evaporated iron as the catalyst. The material was deposited on various substrates as grown directly from the gas phase as films and subsequently characterized by Raman and optical absorption spectroscopies, sheet resistance measurements, electron microscopy, energy-loss spectroscopy, and X-ray photoelectron spectroscopy. The sheet resistance measurements revealed that the doped films had unexpectedly high resistances. This stands in contrast to the case of N-MWCNT films, where decreased resistance has been reported with N-doping. To understand this effect, we developed a resistor network model, which allowed us to disentangle the contribution of bundle−bundle contacts when combined with data on undoped films. Assuming doping does not significantly change the contacts, the increased resistances of the doped films are likely due to enhanced carrier scattering by defect sites in the nanotubes. This work represents the first experimental report on macroscopic N-SWCNT thin films.