Structural and electronic properties of 4 Å carbon nanotubes on Si(001) surfaces

Abstract

The structural and electronic properties of a single-walled 4 Å (3,3) carbon nanotube (CNT) adsorbed on the Si(001) surface are studied using a first-principles method. It is found that for CNTs parallel to the dimer rows, the surface trench is the most stable adsorption site, while CNTs perpendicular to the dimer rows prefer to be adsorbed between Si surface dimers. The stable structures are characterized by four C-Si covalent bonds and large binding energies, 0.38-0.39 eV per unit length of the CNT. The electronic properties of the adsorbed structures are sensitive to the CNT adsorption sites. The structure is semiconducting when the adsorbed CNT is at the trench site, while it is metallic when the CNT is adsorbed between Si dimers. The metal-semiconductor transition of the CNT at the surface trench site is due to the formation of C-Si covalent bonds. The adsorption of a 3 Å (2,2) CNT inside a (6,6) CNT on Si(001) surfaces is also discussed. © 2006 The American Physical Society.