Stone\u2013Wales defects in hexagonal boron nitride as ultraviolet emitters

Hanen Hamdi,Adam Gali,Zoltán Bodrog,Viktor Ivády,Gergő Thiering

doi:10.1038/s41524-020-00451-y

Hanen Hamdi, Adam Gali + Show 3 more

Open Access

https://doi.org/10.1038/s41524-020-00451-y

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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.

Highlights

Two-dimensional (2D) materials are rich in novel phenomena in phyics
We focus our attention to the UV quantum emitter[3] that has a zero-phonon line (ZPL) energy at around 4.08 eV with prominent phonon sideband peaks[3,6]
By integrating the area of ZPL emission and the total emission as plotted in Fig. 1c in ref. 6, its ratio, i.e. the Debye–Waller factor (DW), is ≈0.14 which corresponds to S ≈ 2

Summary

INTRODUCTION

Two-dimensional (2D) materials are rich in novel phenomena in phyics. Hexagonal boron nitride (h-BN) is one of the key 2D materials in the field, which consists of boron–nitrogen bonds in a honeycomb lattice. The first quantum emitters were found to emit in the visible[2] and one in the ultraviolet (UV) region[3] The origin of these emitters is unknown but assumed to come from point defects with states in the fundamental band gap of h-BN2. It can be envisioned in 2D materials that these quantum emitters may be created in a wellcontrolled fashion because the composition of the top layer can be directly manipulated with different techniques We note that this colour centre is distinct from similar UV emitters[8,9] that have ZPL emission at around 4.1 eV but less pronounced phonon sideband with S ≈ 1

RESULTS AND DISCUSSION

Optical properties

Hamdi et al 5

METHODS

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