Single-atom spectroscopy of phosphorus dopants implanted into graphene

TL;DR

This study demonstrates the first atomic-resolution imaging and spectroscopy evidence of phosphorus atoms incorporated into graphene via low-energy ion irradiation, confirming their substitutional lattice position and potential as dopants.

Contribution

It provides the first direct atomic-scale evidence of phosphorus doping in graphene, using advanced imaging and spectroscopy techniques.

Findings

Phosphorus atoms are successfully incorporated into graphene lattice.

P atoms occupy substitutional sites in the graphene structure.

The EELS spectrum matches ab initio simulations, confirming P incorporation.

Abstract

One of the keys behind the success of the modern semiconductor technology has been the ion implantation of silicon, which allows its electronic properties to be tailored. For similar purposes, heteroatoms have been introduced into carbon nanomaterials both during growth and using post-growth methods. However, due to the nature of the samples, it has been challenging to determine whether the heteroatoms have been incorporated into the lattice as intended, with direct observations so far being limited to N and B dopants, and incidental Si impurities. Furthermore, ion implantation of these materials is more challenging due to the requirement of very low ion energies and atomically clean surfaces. Here, we provide the first atomic-resolution imaging and electron energy loss spectroscopy (EELS) evidence of phosphorus atoms incorporated into the graphene lattice by low-energy ion irradiation. The measured P L-edge response of an single-atom EELS spectrum map shows excellent agreement with an ab initio spectrum simulation, conclusively identifying the P in a buckled substitutional configuration. Our results demonstrate the viability of phosphorus as a lattice dopant in $sp^2$-bonded carbon structures and provide its unmistakeable fingerprint for further studies.