Energetics and electronic structure of semiconducting nanotubes adsorbed on surfaces

First-principle calculations are performed to explore the energetics and electronic structures of semiconducting nanotubes adsorbed on the (0 0 0 1) surfaces of α -quartz ( SiO 2 ). We find that the absorption energy of nanotube on SiO 2 is ∼ 0.4 eV/nm , strongly depends on the adsorption site and the inter-unit spacing of the nanotube and the SiO 2 . The electronic structure of this hybrid structure is semiconducting so that the electronic states near the energy gap are caused by those of the nanotubes. A detailed analysis of the electron states of the nanotubes reveals that the energy gaps between valence and conduction bands are slightly modulated by adsorption.