Ultrahigh conductivity of graphene nanoribbons doped with ordered nitrogen

Abstract

Graphene is an attractive candidate for developing high conductivity materials (HCMs) owing to an extraordinary charge mobility. While graphene itself is a semi-metal with an inherently low carrier density, and methods used for increasing carrier density normally also cause a marked decrease in charge mobility. Here, we report that ordered nitrogen doping can induce a pronounced increase in carrier density but does not harm the high charge mobility of graphene nanoribbons (GNRs), giving rise to an unprecedented ultrahigh conductivity in the system. Our first-principles calculations for orderly N-doped GNRs (referred to as C₅N-GNRs) show that N-doping causes a significant shift-up of the Fermi level (ΔE_F), resulting in the presence of multiple partially-filled energy bands (PFEDs) that primarily increase the carrier density of system. Notably, the PFEDs are delocalized well with integral and quantized transmissions, suggesting a negligible effect from N-doping on the charge mobility. Moreover, the PFEDs can cross the E_F multiple times as the ribbon widens, causing the conductivity to increase monotonically and reach ultrahigh values (>15G₀) in sub-5 nm wide ribbons with either armchair or zigzag edges. Furthermore, a simple linear relationship between the doing concentration and the ΔE_F was obtained, which provides a robust means for controlling the conductivity of C₅N-GNRs. Our findings should be useful for understanding the effect of ordered atomic doping on the conductivity of graphene and may open new avenues for realizing graphene-based HCMs.