Electron-Induced State Conversion in Diamond NV Centers Measured with Pump−Probe Cathodoluminescence Spectroscopy

Nitrogen-vacancy (NV) centers in diamond have been exploited as reliable single-photon emitters, with applications in quantum technologies and metrology. Two charge states are known for NV centers: NV0 and NV–, with the latter being mostly studied due to its long electron spin coherence time. Therefore, control over the charge state of the NV centers is essential. However, the understanding of the dynamics between the different states still remains challenging. Here we show that electron excitation induces the conversion from NV– to NV0 through electron-induced carrier generation. We present for the first time ultrafast pump-probe cathodoluminescence spectroscopy, with electron pulses as pump, and laser pulses as probe, to prepare and read out the NV states. The experimental data is explained with a model considering carrier dynamics (0.8 ns), NV0 spontaneous emission (20 ns) and NV0NV– back transfer (500 ms). Our results provide new insights into the NV–NV0 conversion dynamics, and into the use of pump-probe cathodoluminescence as a nanoscale NV characterization tool.