Non-invasive transmission electron microscopy of vacancy defects in graphene produced by ion irradiation

TL;DR

This paper introduces a non-invasive high-resolution electron microscopy method using protective graphene layers to accurately identify vacancy defects in irradiated graphene, clarifying their impact on material properties.

Contribution

It presents a novel non-invasive imaging technique that enables direct atomic-scale defect analysis in graphene without altering the sample during imaging.

Findings

Proton irradiation creates reconstructed monovacancies in graphene.

The technique confirms the nature of defects affecting magnetic and transport properties.

Provides clarity on defect types influencing electronic structure.

Abstract

Irradiation with high-energy ions has been widely suggested as a tool to engineer properties of graphene. Experiments show that it indeed has a strong effect on its transport, magnetic and mechanical characteristics. However, to use ion irradiation as an engineering tool requires understanding of the type and detailed characteristics of the produced defects which is still lacking, as the use of high-resolution transmission electron microscopy (HRTEM) - the only technique allowing direct imaging of atomic-scale defects - often modifies or even creates defects during imaging, thus making it impossible to determine the intrinsic atomic structure. Here we show that encapsulating the studied graphene sample between two other (protective) graphene sheets allows non-invasive HRTEM imaging and reliable identification of atomic-scale defects. Using this simple technique, we demonstrate that proton irradiation of graphene produces reconstructed monovacancies, which explains the profound effect that such defects have on magnetic and transport properties. This finding resolves the existing uncertainty with regard to the effect of ion irradiation on the electronic structure of graphene.