Impurity invisibility in graphene: Symmetry guidelines for the design of efficient sensors

TL;DR

This paper shows that the symmetry of impurity binding in graphene determines its detectability, with symmetric binding leading to invisibility and asymmetry enabling sensing, and strain can break this symmetry to enhance sensor performance.

Contribution

It introduces a symmetry-based framework for predicting impurity visibility in graphene, guiding the design of more effective graphene sensors.

Findings

Symmetric impurity binding causes impurity invisibility in graphene.

Asymmetric dopants are more strongly scattered and detectable.

Strain can break symmetry and turn invisible impurities into detectable ones.

Abstract

Renowned for its sensitivity to detect the presence of numerous substances, graphene is an excellent chemical sensor. Unfortunately, which general features a dopant must have in order to enter the list of substances detectable by graphene are not exactly known. Here we demonstrate with a simple model calculation implemented in three different ways that one of such features is the symmetry properties of the impurity binding to graphene. In particular, we show that electronic scattering is suppressed when dopants are bound symmetrically to both graphene sub-lattices, giving rise to impurity invisibility. In contrast, dopants that affect the two sublattices asymmetrically are more strongly scattered and therefore the most likely candidates to being chemically sensed by graphene. Furthermore, we demonstrate that impurity invisibility is lifted with the introduction of a symmetry-breaking perturbation such as uniaxial strain. In this case, graphene with sublattice-symmetric dopants will function as efficient strain sensors. We argue that by classifying dopants through their bonding symmetry leads to a more efficient way of identifying suitable components for graphene-based sensors.