Transport Properties Of Graphene Nanoribbons Research Articles

Role of Symmetry in the Transport Properties of Graphene Nanoribbons under Bias

The intrinsic transport properties of zigzag graphene nanoribbons (ZGNRs) are investigated using first-principles calculations. It is found that although all ZGNRs have similar metallic band structure, they show distinctly different transport behaviors under bias voltages, depending on whether they are mirror symmetric with respect to the midplane between two edges. Asymmetric ZGNRs behave as conventional conductors with linear current-voltage dependence, while symmetric ZGNRs exhibit unexpected very small currents with the presence of a conductance gap around the Fermi level. This difference is revealed to arise from different coupling between the conducting subbands around the Fermi level, which is dependent on the symmetry of the systems.

Transport properties of graphene nanoribbons with side-attached organic molecules

In this work we address the effects on the conductance of graphene nanoribbons (GNRs) oforganic molecules adsorbed at the ribbon edge. We studied the case of armchair andzigzag GNRs with quasi-one-dimensional side-attached molecules, such as linearpoly-aromatic hydrocarbons and poly(para-phenylene). These nanostructuresare described using a single-band tight-binding Hamiltonian and their electronicconductance and density of states are calculated within the Green’s function formalismbased on real-space renormalization techniques. We found that the conductanceexhibits an even–odd parity effect as a function of the length of the attachedmolecules. Furthermore, the corresponding energy spectrum of the molecules can beobtained as a series of Fano antiresonances in the conductance of the system. Thelatter result suggests that GNRs can be used as a spectrograph sensor device.

Study on electronic structure and transport properties of graphene nanoribbons with single vacancy defects

Based on first-principles electronic structure and transport calculations, we have studied electronic structure and transport properties of graphene nanoribbons with single vacancy defects. It is shown that introduction of the single vacancy defects leads to a flat band belt at the Fermi energy level for graphene nanoribbons and the semiconductor-metal transition in zigzag semiconducting graphene nanoribbons, which is useful in the energy-band engineering. Armchair graphene nanoribbons with odd width are metallic with good electric conduction while armchair graphene nanoribbons with even width have metallic band structures with character of the group IV semiconductor. Single vacancy defects weakens the conduction of armchair graphene nanoribbons with odd width while obviously strengthens the conduction of armchair graphene nanoribbons with even width.

Electronic and Transport Properties of Boron-Doped Graphene Nanoribbons

We report a spin polarized density functional theory study of the electronic and transport properties of graphene nanoribbons doped with boron atoms. We considered hydrogen terminated graphene (nano)ribbons with width up to 3.2 nm. The substitutional boron atoms at the nanoribbon edges (sites of lower energy) suppress the metallic bands near the Fermi level, giving rise to a semiconducting system. These substitutional boron atoms act as scattering centers for the electronic transport along the nanoribbons. We find that the electronic scattering process is spin-anisotropic; namely, the spin-down (up) transmittance channels are weakly (strongly) reduced by the presence of boron atoms. Such anisotropic character can be controlled by the width of the nanoribbon; thus, the spin-up and spin-down transmittance can be tuned along the boron-doped nanoribbons.