Band-gap opening in metallic carbon nanotubes adsorbed on H/Si(001)

A recent scanning tunneling microscope nanolithography technique can fabricate one-dimensional "dangling-bond (DB) wire" by the selective removal of H atoms from a H-passivated Si(001) surface along the Si dimer row. We here theoretically investigate the bonding geometry, band structure, and.binding mechanism of an armchair (3,3) single-walled carbon nanotube (CNT) adsorbed on the DB wire. We find that the formation of C-Si bonds between the CNT and the DB wire gives rise to hybridization between the carbon pi-bond states and the Si dangling-bond states. This hybridization breaks the rotational symmetry of the (3,3) CNT whose pi-bonding and pi-antibonding bands cross at the Fermi level. As a result, the adsorbed CNT opens an energy gap of similar to 0.1 eV, yielding a metal-to-semiconductor transition. (c) 2006 American Institute of Physics.