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 π-bond states and the Si dangling-bond states. This hybridization breaks the rotational symmetry of the (3,3) CNT whose π-bonding and π-antibonding bands cross at the Fermi level. As a result, the adsorbed CNT opens an energy gap of ∼0.1 eV, yielding a metal-to-semiconductor transition. [ABSTRACT FROM AUTHOR]