Effects of Geometry and Symmetry on Electron Transport through Graphene-Carbon-Chain Junctions

TL;DR

This study investigates how the geometry and symmetry of carbon chains connecting graphene nanoribbons influence electron transport, revealing ways to control conductance and electronic behavior in nanoscale devices.

Contribution

It demonstrates the critical role of orbital symmetry and contact geometry in modulating electron transport in graphene-carbon-chain junctions, introducing new ways to engineer device functionalities.

Findings

Symmetry of orbitals determines electron transport modes.

Position and number of carbon chains affect conductance near Fermi energy.

Proper geometry enables Ohmic contact, current stabilization, or negative differential resistance.

Abstract

The electron transport between two zigzag graphene nanoribbons (ZGNRs) connected by carbon atomic chains has been investigated by the nonequilibrium Green's function method combined with the density functional theory. The symmetry of the orbitals in the carbon chain selects critically the modes and energies of the transporting electrons. The electron transport near the Fermi energy can be well-manipulated by the position and the number of carbon chains contacting the nanoribbons. In symmetric ZGNRs connected by a central carbon chain, a square conductance step appears at the Fermi energy because the antisymmetric modes below it are not allowed to go through the chain. These modes can additionally contribute to the conductance if side carbon chains are added in the connection. By choosing a proper geometry configuration, we can realize Ohmic contact, current stabilizer, or the negative differential resistance phenomenon in the devices.