Impurity segregation in graphene nanoribbons

TL;DR

This paper models impurity segregation in graphene nanoribbons, showing how impurity distribution can be controlled by external electric fields, potentially tuning their magnetic and transport properties.

Contribution

A simple energy model for impurity positioning in GNRs validated by ab initio calculations, highlighting external electric fields as a control mechanism.

Findings

Impurities tend to segregate near edges due to energetic favorability.

External electric fields can influence impurity distribution across the ribbon.

Control over impurity placement may enable tuning of GNR properties.

Abstract

The electronic properties of low-dimensional materials can be engineered by doping, but in the case of graphene nanoribbons (GNR) the proximity of two symmetry-breaking edges introduces an additional dependence on the location of an impurity across the width of the ribbon. This introduces energetically favorable locations for impurities, leading to a degree of spatial segregation in the impurity concentration. We develop a simple model to calculate the change in energy of a GNR system with an arbitrary impurity as that impurity is moved across the ribbon and validate its findings by comparison with ab initio calculations. Although our results agree with previous works predicting the dominance of edge disorder in GNR, we argue that the distribution of adsorbed impurities across a ribbon may be controllable by external factors, namely an applied electric field. We propose that this control over impurity segregation may allow manipulation and fine-tuning of the magnetic and transport properties of GNRs.