Stability and electronic properties of carbon nanotubes adsorbed on Si(0 0 1)

We report first-principles calculations on the adsorption of an armchair (6,6) single-walled carbon nanotube (CNT) on the Si(001) surface. We study several well-ordered adsorption configurations for the nanotube on the Si surface. Our results show stable geometries between two consecutive Si-dimer rows (the surface trench). The binding energy per tube length for the CNT in the most stable geometry is calculated to be 0.2 eV/Å. In this geometry, we observe the formation of C-Si chemical bonds. The density of states along the dimer rows for the lowest-energy adsorbed configuration shows an increase in the number of states at the Fermi level. This suggests an enhancement of the nanotube metallic character throughout the contact with the Si surface due to the formation of the C-Si bonds. These properties may lead to consider metallic CNTs as one-dimensional wires on the silicon surface with promising applications for contact and interconnections of future nanoscale electronic devices.