Quantum conductance of graphene nanoribbons with edge defects

Abstract

The conductance of metallic graphene nanoribbons (GNRs) with single defects and weak disorder at their edges is investigated in a tight-binding model. We find that a single edge defect will induce quasi-localized states and consequently cause zero-conductance dips. The center energies and breadths of such dips are strongly dependent on the geometry of GNRs. Armchair GNRs are much more sensitive to a vacancy than zigzag GNRs, but are less sensitive to a weak scatter. More importantly, we find that with a weak disorder, zigzag GNRs will change from metallic to semiconducting due to Anderson localization. But a weak disorder only slightly affects the conductance of armchair GNRs. The influence of edge defects on the conductance will decrease when the widths of GNRs increase.Comment: 8 pages and 11 figure

Structure of graphene and its disorders: a review

“…Point defects such as SW defects, vacancies, and adatoms can serve as scattering centers for electron waves, and thus reducing the conductivity of graphene [255–258]. The charged impurities adsorbed on graphene or located at the interface between graphene and substrate induce Coulomb scattering [259], and are responsible for the electron-hole puddles at the neutrality point [260,261].…”

Charge transport in disordered graphene-based low dimensional materials

“…The basic idea is to start from a tight-binding Hamiltonian for a clean and regular ribbon (in general with hydrogen passivation on the edges), and then adding [37] or removing [36, 139 141] carbon atoms at the edges, or varying the width of the system [142] to account for roughness, or introducing Anderson disorder [143]. The most proper way of adding/removing atoms at the edges avoids fi nal confi gurations that might cause steric problems.…”

“…The transport properties of metallic aGNRs have been investigated in the presence of both roughness [36,141] and Anderson disorder [143] on the edges. In the case of vacancies on the edges, the differential conductance of the system is considerably reduced and even a weak disorder on the two external rows induces a localization process, see Fig.…”

Quantized conductance of a suspended graphene nanoconstriction

“…However, those devices are not in the ballistic regime because they have the characteristics of a diffusive, disordered system and lack uniform doping owing to strong interaction with the substrate. In such a narrow and long ribbon an edge disorder of typically only a few per cent of missing carbon atoms will prevent the observation of quantum ballistic transport and conductance quantization [17][18][19] . A way to circumvent this problem is to prepare a constriction with a length comparable or shorter than the width, for which conductance quantization is theoretically possible for an edge disorder of 10% or even higher [18][19][20] .…”