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

Abstract

Nitrogen-vacancy (NV) centers in diamond are reliable single-photon emitters, with applications in quantum technologies and metrology. Two charge states are known for NV centers: NV 0 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, an understanding of the dynamics between the different states still remains challenging. Here, conversion from NVto NV 0 due to electron-induced carrier generation is shown. Ultrafast pump-probe cathodoluminescence spectroscopy is presented for the first time, 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), NV 0 spontaneous emission (20 ns) and NV 0 NVback transfer (500 ms). The results provide new insights into the NV -NV 0 conversion dynamics, and into the use of pumpprobe cathodoluminescence as a nanoscale NV characterization tool.Nitrogen-vacancy (NV) centers in diamond are promising elements for quantum optical systems since they are single-photon emitters 1,2 with high photostability, quantum yield and brightness, even at room temperature. 3-6 Moreover, they are integrated inside a widebandgap solid-state host, the diamond lattice, making them robust against decoherence and allowing device scalability. 7-9 NV centers exhibit two different configurational states, the NV 0 state, with a zero-phonon line (ZPL) at 2.156 eV (λ = 575 nm), and the NVstate, with a ZPL at 1.945 eV (λ = 637 nm). 2 NV centers in the NVstate have received most of the attention in the past years since they exhibit a long electron spin coherence time that can be optically manipulated and read out, 9,10 which, together with the characteristics mentioned previously, make them suitable as building blocks for quantum technologies, 9,11,12 nanoscale magnetometry, 13,14 and other applications. 15,16 Typically, synthetically prepared diamonds with NV centers contain both NV 0 and NVstates. Previous work has shown that the state of an NV center can be converted from NVto NV 0 (ionization) and vice versa (recombination). For example, the state of the NV centers can be changed by laser irradiation [17][18][19] , as well as by shifting the Fermi level, either chemically, [20][21][22] or by applying an external voltage 23,24 .

Cathodoluminescence of green fluorescent protein exhibits the redshifted spectrum and the robustness

“…While PL shows the emission from both negatively-charged and neutral states, CL exhibits the emission only from neutral state. This fact is also surprising and its mechanism was recently studied 9 . Here, we emphasize the difference between diamond NV centre and GFP.…”

Tailoring of Typical Color Centers in Diamond for Photonics

“…Throughout the current literature, the charge‐state regulation of NV centers can be summarized as the electronic transition regulation and Fermi‐level regulation. [ 55–63 ] The former controls the electron transition path using an excitation laser of different wavelengths and power [ 56–64 ] to optimize the radiation spectrum generated by electron transition (Section 3.2); the latter adjusts the Fermi energy level of the color center location in the crystal [ 58,65,66 ] by employing surface terminal modification, electrochemistry, and an electric field (Section 3.3).…”

Orientation Dependence of Cathodoluminescence and Photoluminescence Spectroscopy of Defects in Chemical-Vapor-Deposited Diamond Microcrystal

“…The nitrogen vacancy related defects are among the essential ones in diamonds due to potential photonics applications. They can exist in two configurations [24]: nitrogen-neutral vacancy (NV 0 ) observed at 2.156 eV in CL and PL spectra, and negatively charged nitrogen vacancy (NV − ) at 1.945 eV. The last one is of the most important centers in diamond (possible Qubit).…”