Stability of extended defects on boron nitride and graphene monolayers: the role of chemical environment

TL;DR

This study uses ab initio calculations to analyze how the stability of antiphase boundaries in boron nitride and graphene monolayers depends on chemical environment, revealing conditions favoring different defect structures and their electronic properties.

Contribution

It introduces a detailed understanding of how chemical potentials influence the stability and electronic structure of extended defects in 2D materials.

Findings

Zigzag APBs are stable in N-rich environments.

Armchair APBs are stable under B-rich or intrinsic conditions.

Carbon doping stabilizes zigzag APBs near N-rich limit.

Abstract

We perform ab initio calculations that indicate that the relative stability of antiphase boundaries (APB) with armchair and zigzag chiralities in monolayer boron nitride (BN) is determined by the chemical potentials of the boron and nitrogen species in the synthesis process. In an N-rich environment, a zigzag APB with N-rich core is the most stable structure, while under B-rich or intrinsic growth conditions, an armchair APB with stoichiometric core is the most stable. This stability transition is shown to arise from a competition between homopolar-bond (B-B and N-N) and elastic energy costs in the core of the APBs. Moreover, in the presence of a carbon source we find that a carbon-doped zigzag APB becomes the most stable boundary near the N-rich limit. The electronic structure of the two types of APBs in BN is shown to be particularly distinct, with the zigzag APB depicting defect-like deep electronic bands in the band gap, while the armchair APB shows bulk-like shallow electronic bands.