Single Photon Emitters in Boron Nitride: More Than a Supplementary Material

TL;DR

This study thoroughly characterizes single photon emitters in boron nitride, revealing their optical properties, stability, excitation dependence, and potential for room-temperature quantum applications.

Contribution

It provides the first comprehensive optical analysis of boron nitride single photon sources, highlighting their stability, excitation selectivity, and insensitivity to magnetic fields.

Findings

Emitters are stable and suitable as visible light sources.

Emission intensity depends on excitation energy and polarization.

Magnetic field has no effect on emission spectra.

Abstract

We present comprehensive optical studies of recently discovered single photon sources in boron nitride, which appear in form of narrow lines emitting centres. Here, we aim to compactly characterise their basic optical properties, including the demonstration of several novel findings, in order to inspire discussion about their origin and utility. Initial inspection reveals the presence of narrow emission lines in boron nitride powder and exfoliated flakes of hexagonal boron nitride deposited on Si/SiO2 substrates. Generally rather stable, the boron nitride emitters constitute a good quality visible light source. However, as briefly discussed, certain specimens reveal a peculiar type of blinking effects, which are likely related to existence of meta-stable electronic states. More advanced characterisation of representative stable emitting centres uncovers a strong dependence of the emission intensity on the energy and polarisation of excitation. On this basis, we speculate that rather strict excitation selectivity is an important factor determining the character of the emission spectra, which allows the observation of single and well-isolated emitters. Finally, we investigate the properties of the emitting centres in varying external conditions. Quite surprisingly, it is found that the application of a magnetic field introduces no change in the emission spectra of boron nitride emitters. Further analysis of the impact of temperature on the emission spectra and the features seen in second-order correlation functions is used to provide an assessment of the potential functionality of boron nitride emitters as single photon sources capable of room temperature operation.