Implanting germanium into graphene

TL;DR

This study demonstrates that heavy germanium atoms can be implanted into graphene, enabling tailored properties and potential applications like single-atom catalysis, with detailed atomistic insights into the implantation process.

Contribution

It is the first to show heavy Ge atom implantation into graphene and provides atomic-level understanding of the process and configurations.

Findings

Ge can substitute or occupy divacancies in graphene

Implantation occurs below the displacement threshold energy

Heavy atoms can be incorporated into the graphene lattice

Abstract

Incorporating heteroatoms into the graphene lattice may be used to tailor its electronic, mechanical and chemical properties. Direct substitutions have thus far been limited to incidental Si impurities and P, N and B dopants introduced using low-energy ion implantation. We present here the heaviest impurity to date, namely $^{74}$Ge$^+$ ions implanted into monolayer graphene. Although sample contamination remains an issue, atomic resolution scanning transmission electron microscopy imaging and quantitative image simulations show that Ge can either directly substitute single atoms, bonding to three carbon neighbors in a buckled out-of-plane configuration, or occupy an in-plane position in a divacancy. First principles molecular dynamics provides further atomistic insight into the implantation process, revealing a strong chemical effect that enables implantation below the graphene displacement threshold energy. Our results show that heavy atoms can be implanted into the graphene lattice, pointing a way towards advanced applications such as single-atom catalysis with graphene as the template.