Spatial segregation of substitutional B atoms in graphene patterned by the moir\'e superlattice on Ir(111)

TL;DR

This study demonstrates how moiré patterns in graphene on Ir(111) guide the formation of ordered arrays of substitutional boron atoms, revealing their distribution, bonding, and minimal impact on electronic properties through combined experimental and theoretical methods.

Contribution

It provides a detailed understanding of boron atom segregation and behavior in graphene moiré patterns, combining microscopy, spectroscopy, and density functional theory analysis.

Findings

Boron forms small aggregates in low regions of the moiré superlattice.

Local graphene rippling influences boron distribution and electronic interactions.

Boron incorporation does not significantly alter graphene's electronic structure.

Abstract

Fabrication of ordered structures at the nanoscale limit poses a cornerstone challenge for modern technologies. In this work we show how naturally occurring moir\'e patterns in Ir(111)-supported graphene template the formation of 2D ordered arrays of substitutional boron species. A complementary experimental and theoretical approach provides a comprehensive description of the boron species distribution, bonding configurations, interfacial interaction with Ir(111) and the impact on graphene's electronic structure. Atomically-resolved scanning tunnelling microscopy images and density functional theory calculations reveal that boron preferably forms small aggregates of substitutional defects in geometrically low regions of the moir\'e superlattice of graphene, by inducing local bending of graphene towards the underlying Ir(111). Surprisingly, calculations reveal that the incorporation of electron deficient boron does not lead to an enhanced p-type doping, as the local rippling of the graphene layer prompts electron uptake from the iridium substrate that compensates the initial electron loss due to substitutional boron. Scanning tunnelling spectroscopy and angle-resolved photoemission spectroscopy measurements corroborate that the arrays of boron species do not modify the electronic structure of graphene near the Fermi level, hence preserving the slight p-type doping induced by Ir(111).