[Paper Review] On the effect of Edge vs bulk effects in Graphene Nanoribbons

Colm Durkan, Xiao Liu+1 more|arXiv (Cornell University)|Feb 13, 2026

Graphene research and applications0 citations

TL;DR

The paper uses computational modeling and high-resolution Scanning Gate Microscopy to assess whether edge versus bulk properties drive the width-dependent CNP sign change in graphene nanoribbons (GNRs), finding edges do not dominantly cause the sign change and suggesting size-dependent band-structure effects instead.

ABSTRACT

Recent works have shown how the electrical properties of graphene nanoribbons (GNRs) show a size-dependence in terms of resistivity, charge neutrality point (CNP) and band structure once their widths drop below approximately 50 nm. It has been observed that the CNP switches sign below a certain GNR width, and in this article, we explore this via computational modelling of the electric field and the conductance of GNRs in the presence of an AFM tip. We show that CNP is expected to shift towards lower values as GNR width reduces as a result of the significantly enhanced electric field around edges, but that a change in sign is not expected. We also show experimentally via high-resolution Scanning Gate Microscopy (SGM) that there does not appear to be any significant difference between the edges and the bulk of a GNR, indicating that the switch in CNP is not due to differential doping, and may instead be due to variations in the band structure as a function of size.

Motivation & Objective

• Investigate how GNR width below ~50 nm affects resistivity, CNP, and band structure.
• Assess whether edge effects vs bulk properties drive CNP sign changes.
• Use computational modeling of electric fields and conductance with an AFM tip.
• Validate findings with experimental high-resolution Scanning Gate Microscopy (SGM).
• Determine implications for whether observed CNP shifts are due to doping or band-structure variations.

Proposed method

• Compute electric field and conductance in GNRs in the presence of an AFM tip to model edge versus bulk scenarios.
• Perform high-resolution Scanning Gate Microscopy (SGM) experiments to probe edge vs bulk behavior in GNRs.
• Compare CNP trends with GNR width and analyze sign changes.
• Infer whether edge-induced doping or alternative mechanisms explain CNP behavior.

Experimental results

Research questions

• RQ1 Does the CNP sign change in graphene nanoribbons with decreasing width arise from edge versus bulk effects?
• RQ2 How does the electric field enhancement near edges influence CNP and resistivity in narrow GNRs?
• RQ3 Are observed width-dependent CNP shifts due to differential edge doping or changes in band structure with size?
• RQ4 What do high-resolution SGM measurements reveal about edge versus bulk contributions to GNR electronic properties?
• RQ5 What mechanisms best explain the size-dependent electronic behavior of GNRs below ~50 nm?

Key findings

• CNP is expected to shift toward lower values as GNR width decreases due to enhanced edge electric fields.
• No sign change in CNP is expected from edge versus bulk differentiation.
• Experimental SGM indicates little difference between edge and bulk regions in GNRs.
• The CNP switch is likely not caused by differential edge doping but by size-dependent band-structure variations.
• The work supports a band-structure–driven explanation for width-dependent electronic changes in GNRs.