Supergrowth of nitrogen-doped single-walled carbon nanotube arrays: active species, dopant characterization, and doped/undoped heterojunctions.

We demonstrate the water-assisted supergrowth of vertically aligned single-walled carbon-nitrogen nanotubes (SWNNTs) using a simple liquid/gas-phase precursor system. In situ characterization of gas-phase nitrogen-containing precursors and their correlation to growth identifies HCN as the most active precursor for SWNNT growth, analogous to C(2)H(2) for single-walled carbon nanotubes (SWNTs). Utilizing Raman spectroscopy, combined with XPS and in situ mass spectrometry during growth, we demonstrate the ability to probe N atoms at low concentrations (10(-5) at. % N) in the SWNNT. Additionally, we demonstrate sensitivity of SWNNT optical transitions to N-doping through absorbance measurements, which appear to be a sensitive fingerprint for SWNNT doping. Finally, we demonstrate the fabrication of SWNT/SWNNT heterojunctions in the self-assembled carpet morphology that can be printed to arbitrary host substrates and facilitate potential emerging applications for this material. This work brings together new aspects regarding the growth, characterization, and materials processing that can yield advanced material architectures involving electronically tuned SWNNT array networks.