First-Principles Calculations of Carbon Nanotubes Adsorbed on Si(001)

We report first-principles calculations on the adsorption of a metallic (6,6) single-walled carbon nanotube (SWCN) on the Si(001) surface. We find stable geometries for the nanotube between two consecutive dimer rows where C-Si chemical bonds are formed. The binding energy in the most stable geometry is found to be $0.2\mathrm{e}\mathrm{V}/\AA$. Concerning the electronic properties, the most stable structure shows an increase in the density of states near the Fermi level due to the formation of C-Si bonds enhancing the metallic character of the nanotube by the contact with the surface. These properties may lead one to consider metallic SWCNs adsorbed on Si substrates for interconnections and contacts on future nanoscale devices. Finally, the nature of the nanotube-surface interaction for nanotubes of larger diameters is also discussed.