Room-temperature quantum emission from $\mathrm{C}{\mathrm{u}}_{\mathrm{Zn}}$-${\mathrm{V}}_{\mathrm{S}}$ defects in ZnS:Cu colloidal nanocrystals

Abstract

We report room-temperature observations of $\mathrm{C}{\mathrm{u}}_{\mathrm{Zn}}$-${\mathrm{V}}_{\mathrm{S}}$ quantum emitters in individual ZnS:Cu nanocrystals (NCs). Using time-gated imaging, we isolate the distinct, $\sim$3-$\hat{I}¼$s-long, red photoluminescence (PL) emission of $\mathrm{C}{\mathrm{u}}_{\mathrm{Zn}}$-${\mathrm{V}}_{\mathrm{S}}$ defects, enabling their precise identification and statistical characterization. The emitters exhibit distinct blinking and photon antibunching, consistent with individual NCs containing two to four $\mathrm{C}{\mathrm{u}}_{\mathrm{Zn}}$-${\mathrm{V}}_{\mathrm{S}}$ 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 $\ddot{I}ƒ$-character optical dipole transition and the symmetry of the $\mathrm{C}{\mathrm{u}}_{\mathrm{Zn}}$-${\mathrm{V}}_{\mathrm{S}}$ defect. These observations motivate further investigation of $\mathrm{C}{\mathrm{u}}_{\mathrm{Zn}}$-${\mathrm{V}}_{\mathrm{S}}$ defects in ZnS NCs for use in quantum technologies.

29 pages, 17 figures