Electronic properties of nanotube–ribbon hybrid systems

Abstract

In this work we use the tight-binding model to study the electronic properties ofnanotube–ribbon hybrid systems. The nanotube–ribbon interactions will modify state energies,alter energy gaps, destroy state degeneracy, and create additional band-edge states. Thebandstructures are asymmetric and symmetric about the Fermi energy when theinteractions are turned on and off, respectively. The energy gap is found to vary sensitivelywith the nanotube location. Moreover, semiconductor–metal transition is predicted fornanotube–ribbon hybrid systems (I) and (III). For a zigzag ribbon, the partial flat bands atEF are almost unaffected by the nanotube–ribbon coupling although the bandstructures havebeen noticeably modified by such coupling; the energy gap of system (IV) is always zero.The effects of nanotube diameter and ribbon width on the energy gap and the density ofstates are also investigated. The semiconductor–metal transition can be accomplished byvarying the nanotube location, the nanotube diameter or the ribbon width. The mainfeatures of the bandstructure are directly reflected in the density of states. The numbers,heights, and energies of the density of states peaks are strongly dependent on thenanotube–ribbon hoppings.