Room-temperature quantum emission from $\mathrm{Cu_{Zn}}$-$\mathrm{V_{S}}$ defects in ZnS:Cu colloidal nanocrystals

TL;DR

This study demonstrates room-temperature quantum light emission from specific copper-related defects in ZnS nanocrystals, with detailed characterization of their optical properties and potential for quantum technology applications.

Contribution

First observation and detailed analysis of room-temperature quantum emitters from $ ext{Cu}_{ ext{Zn}}$-$ ext{V}_ ext{S}$ defects in ZnS:Cu nanocrystals, including their optical behavior and polarization characteristics.

Findings

Distinct $ ext{Cu}_{ ext{Zn}}$-$ ext{V}_ ext{S}$ defect emission with ~3 μs PL lifetime

Emitters show blinking and photon antibunching, indicating single-photon emission

PL spectra exhibit a blue shift due to photochemical effects

Abstract

We report room-temperature observations of $\mathrm{Cu_{Zn}}$-$\mathrm{V_{S}}$ quantum emitters in individual ZnS:Cu nanocrystals (NCs). Using time-gated imaging, we isolate the distinct, $\sim$3-$\mu$s-long, red photoluminescence (PL) emission of $\mathrm{Cu_{Zn}}$-$\mathrm{V_{S}}$ defects, enabling their precise identification and statistical characterization. The emitters exhibit distinct blinking and photon antibunching, consistent with individual NCs containing two to four $\mathrm{Cu_{Zn}}$-$\mathrm{V_{S}}$ defects. The quantum emitters' PL spectra show a pronounced blue shift compared to NC dispersions, likely due to photochemical and charging effects. Emission polarization measurements of quantum emitters are consistent with a $\sigma$-character optical dipole transition and the symmetry of the $\mathrm{Cu_{Zn}}$-$\mathrm{V_{S}}$ defect. These observations motivate further investigation of $\mathrm{Cu_{Zn}}$-$\mathrm{V_{S}}$ defects in ZnS NCs for use in quantum technologies.