Exploring the carbon nanocosmos: Doped nanotubes, networks, and other novel forms of carbon

High temperature routes to arrays of aligned CN_x nanotubes and B-doped carbon nanotubes are presented. The materials have been characterized using state-of-the-art techniques such as high-resolution electron energy loss spectroscopy (HREELS), scanning tunneling spectroscopy (STS) and high-resolution transmission electron microscopy (HRTEM). Using STS, we show that the doped nanotubes exhibit strong features on the conduction (for CN_x nanotubes) and valence band (for B-doped nanotubes) close to the Fermi level, thus indicating that electron-rich (CN_x) and hole-rich (B-doped) nanotubes are indeed fabricated (n- and p-type respectively). Tight-binding and ab-inito calculations confirm our experimental results obtained using STS. Finally, it is demonstrated that high electron irradiation at 700 - 800°C, is capable of creating "X" and "Y" junctions using single-walled nanotubes (SWNTs). The process has also been studied using tight-binding molecular dynamics (TBMD). Vacancies trigger the organization of atoms on the tube lattices within adjacent tubes. These results pave the way to the fabrication of nanotube heterojunction networks, robust composites, contacts, nanocircuits and strong 3D composites.