Stone-Wales defects in hexagonal boron nitride as ultraviolet emitters

TL;DR

This study uses first principles calculations to identify Stone-Wales defects in hexagonal boron nitride as ultraviolet light emitters, potentially changing how fluorescent centers are understood in this material.

Contribution

It demonstrates that specific Stone-Wales defects are responsible for ultraviolet emission in hexagonal boron nitride, providing a new understanding of its optical properties.

Findings

Pentagon-heptagon Stone-Wales defect emits at 4.08 eV, matching observed quantum emitters.

Square-octagon line defects are also optically active in the ultraviolet region.

Results suggest a new paradigm for identifying fluorescent centers in hexagonal boron nitride.

Abstract

Many quantum emitters have been measured close or near the grain boundaries of the two-dimensional hexagonal boron nitride where various Stone-Wales defects appear. We show by means of first principles density functional theory calculations that the pentagon-heptagon Stone-Wales defect is an ultraviolet emitter and its optical properties closely follow the characteristics of a 4.08-eV quantum emitter often observed in polycrystalline hexagonal boron nitride. We also show that the square-octagon Stone-Wales line defects are optically active in the ultraviolet region with varying gaps depending on their density in hexagonal boron nitride. Our results may introduce a paradigm shift in the identification of fluorescent centres in this material.