Model of impurity segregation in graphene nanoribbons

The electronic properties of low-dimensional materials can be engineered by doping, but in the case of graphene nanoribbons (GNRs) 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 describe how the change in energy of a GNR system doped with a single impurity depends on the impurity position. The model is validated by comparing its findings 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.