Abstract

The stability and bonding properties of capped single-walled carbon nanotubes (CNTs) adsorbed on the Si(001) surface are addressed by density-functional theory calculations. We study the armchair (5,5) and the zigzag (9,0) CNTs with a similar length of about 24 Å, which are adsorbed parallel and perpendicular to the dimer direction of the reconstructed Si(001) surface. At the equilibrium geometries, both CNTs form covalent bonds with the substrates with binding energies ranging from 0.40 to 0.62 eV per C-Si bond. These bonds only form when neighboring C and Si atoms are closer than 2.13 Å. We find a preferential direction for the CNT adsorptions along the dimers where the zigzag CNT is found to be the most stable. Changes in the Si(001) band structures after the CNT adsorption are also discussed. © 2008 American Institute of Physics.