Defect-engineering hexagonal boron nitride using low-energy Ar+ irradiation

TL;DR

This study demonstrates how low-energy Ar+ ion irradiation can selectively engineer defect types in monolayer hexagonal boron nitride, advancing the control of quantum emitter-related defects for future applications.

Contribution

It provides the first detailed correlation between ion irradiation parameters and defect types in hBN, enabling targeted defect engineering.

Findings

Intrinsic defect concentration is about 0.03/nm2.

Irradiation increases defect concentration to 0.30/nm2.

Irradiation selectively alters defect type distributions.

Abstract

Monolayer hexagonal boron nitride (hBN) has recently become the focus of intense research as a material to host quantum emitters. Although it is well known that such emission is associated with point defects, so far no conclusive correlation between the spectra and specific defects has been demonstrated. Here, we prepare atomically clean suspended hBN samples and subject them to low-energy ion irradiation. The samples are characterized before and after irradiation via automated scanning transmission electron microscopy imaging to assess the defect concentrations and distributions. We find an intrinsic defect concentration of ca. 0.03/nm2 (with ca. 55% boron and 8% nitrogen single vacancies, 20% double vacancies and 16% more complex vacancy structures). To be able to differentiate between these and irradiation-induced defects, we create a significantly higher (but still moderate) concentration of defects with the ions (0.30/nm2), and now find ca. 55% boron and 12% nitrogen single vacancies, 14% double vacancies, and 18% more complex vacancy structures. The results demonstrate that already the simplest irradiation provides selectivity for the defect types, and open the way for future experiments to explore changing the selectivity by modifying the irradiation parameters.