Conductance of graphene flakes contacted at their corners

TL;DR

This study computationally analyzes how the geometry and edge type of graphene flakes influence their electrical conductance when contacted at corners, revealing significant differences based on edge configuration and contact position.

Contribution

It demonstrates that contact placement at corners and edge type critically affect conductance, with new insights into the role of edge states and disorder effects in graphene junctions.

Findings

Armchair-edge flakes with electrodes at acute corners block conductance.

Electrodes at obtuse corners enhance conductance in armchair-edge flakes.

Edge disorder does not significantly alter main conductance trends.

Abstract

Linear conductance of junctions formed by graphene flakes with order of nanometer-thick electrodes attached at the corners of the flakes is studied. The explored structures have sizes up to 20000 atoms and the conductance is studied as a function of applied gate voltage varied around the Fermi level. The finding, obtained computationally, is that junctions formed by armchair-edge flakes with the electrodes connected at the acute-angle corners block the electron transport while only junctions with such electrodes at the obtuse-angle corners tend to provide the high electrical conductance typical for metallic GNRs. The finding in case of zig-zag edges is similar with an exception of a relatively narrow gate voltage interval in which each studied junction is highly conductive as mediated by the edge states. The contrast between the conductive and insulating setups is typically several orders of magnitude in terms of ratio of their conductances. Main results of the paper remain to a large extent valid also in the presence of edge disorder.