Atomically well-defined nitrogen doping for cross-plane transport through graphene heterojunctions

The nitrogen doping of graphene leads to graphene heterojunctions with a tunable bandgap, suitable for electronic, electrochemical, and sensing applications. However, the microscopic nature and charge transport properties of atomic-level nitrogen-doped graphene are still unknown, mainly due to the multiple doping sites with topological diversities. In this work, we fabricated atomically well-defined N-doped graphene heterojunctions and investigated the cross-plane transport through these heterojunctions to reveal the effects of doping on their electronic properties. We found that a different doping number of nitrogen atoms leads to a conductance difference of up to similar to 288%, and the conductance of graphene heterojunctions with nitrogen-doping at different positions in the conjugated framework can also lead to a conductance difference of similar to 170%. Combined ultraviolet photoelectron spectroscopy measurements and theoretical calculations reveal that the insertion of nitrogen atoms into the conjugation framework significantly stabilizes the frontier molecular orbitals, leading to a change in the relative positions of the HOMO and LUMO to the Fermi level of the electrodes. Our work provides a unique insight into the role of nitrogen doping in the charge transport through graphene heterojunctions and materials at the single atomic level.

Automated summary

Nitrogen doping of graphene leads to graphene heterojunctions with a tunable bandgap, suitable for various applications. In this work, atomically well-defined N-doped graphene heterojunctions were fabricated and their electronic properties were investigated. It was found that different doping numbers and positions of nitrogen atoms affected the conductance of the heterojunctions significantly. Furthermore, the insertion of nitrogen atoms into the conjugation framework of graphene stabilized the molecular orbitals and altered their relative positions to the Fermi level of the electrodes.