First-principles identification of single photon emitters based on carbon clusters in hexagonal boron nitride

TL;DR

This study uses density-functional theory to identify carbon clusters in hexagonal boron nitride as potential single photon emitters, matching experimental photoluminescence spectra and highlighting the role of specific carbon conformations.

Contribution

It provides a first-principles analysis of carbon cluster configurations in h-BN as single photon emitters, linking theoretical spectra to experimental observations.

Findings

Certain carbon cluster conformations match experimental photoluminescence spectra.

Vacancies do not reproduce typical phonon sideband features.

Carbon clusters are likely responsible for observed SPEs in h-BN.

Abstract

A recent study associate carbon with single photon emitters (SPEs) in hexagonal boron nitride (h-BN). This observation, together with the high mobility of carbon in h-BN suggest the existence of SPEs based on carbon clusters. Here, by means of density-functional theory calculations we studied clusters of substitutional carbon atoms up to tetramers in hexagonal boron nitride. Two different conformations of neutral carbon trimers have zero-point line energies and shifts of the phonon sideband compatible with typical photoluminescence spectra. Moreover, some conformations of two small C clusters next to each other result in photoluminescence spectra similar to those found in experiments. We also showed that vacancies are unable to reproduce the typical features of the phonon sideband observed in most measurements due to the large spectral weight of low-energy breathing modes, ubiquitous in such defects.