Group IV vacancy color centers in diamond are promising spin-photon interfaces with strong potential for applications in photonic quantum technologies. Reliable methods for controlling and stabilizing their charge state are urgently needed for scaling to multiqubit devices. Here, we manipulate the charge state of silicon vacancy (SiV) ensembles by combining luminescence and photocurrent spectroscopy. We controllably convert the charge state between the optically active SiV − and dark SiV 2− with megahertz rates and >90% contrast by judiciously choosing the local potential applied to in-plane surface electrodes and the laser excitation wavelength. We observe intense SiV − photoluminescence under hole capture, measure the intrinsic conversion time from the dark SiV 2− to the bright SiV − to be 36.4(67) ms, and demonstrate how it can be enhanced by a factor of 10 5 via optical pumping. Moreover, we obtain previously unknown information on the defects that contribute to photoconductivity, indicating the presence of substitutional nitrogen and divacancies.
Group IV vacancy color centers in diamond are promising spin-photon interfaces with strong potential for applications in photonic quantum technologies. Reliable methods for controlling and stabilizing their charge state are urgently needed for scaling to multiqubit devices. Here, we manipulate the charge state of silicon vacancy (SiV) ensembles by combining luminescence and photocurrent spectroscopy. We controllably convert the charge state between the optically active SiV − and dark SiV 2− with megahertz rates and >90% contrast by judiciously choosing the local potential applied to in-plane surface electrodes and the laser excitation wavelength. We observe intense SiV − photoluminescence under hole capture, measure the intrinsic conversion time from the dark SiV 2− to the bright SiV − to be 36.4(67) ms, and demonstrate how it can be enhanced by a factor of 10 5 via optical pumping. Moreover, we obtain previously unknown information on the defects that contribute to photoconductivity, indicating the presence of substitutional nitrogen and divacancies.
Control over the charge states of color centers in solids is necessary to fully utilize them in quantum technologies. However, the microscopic charge dynamics of deep defects in wide-band-gap semiconductors are complex, and much remains unknown. We utilize a single-shot charge-state readout of an individual nitrogen-vacancy (NV) center to probe the charge dynamics of the surrounding defects in diamond. We show that the NV center charge state can be converted through the capture of holes produced by optical illumination of defects many micrometers away. With this method, we study the optical charge conversion of silicon-vacancy (SiV) centers and provide evidence that the dark state of the SiV center under optical illumination is SiV 2– . These measurements illustrate that charge carrier generation, transport, and capture are important considerations in the design and implementation of quantum devices with color centers and provide a novel way to probe and control charge dynamics in diamond.
Abstract Nitrogen-vacancy (NV) and silicon-vacancy (SiV) color defects in diamond are promising systems for applications in quantum technology. The NV and SiV centers have multiple charge states, and their charge states have different electronic, optical and spin properties. For the NV centers, most investigations for quantum sensing applications are targeted on the negatively charged NV (NV−), and it is important for the NV centers to be in the NV− state. However, it is known that the NV centers are converted to the neutrally charged state (NV0) under laser excitation. An energetically favorable charge state for the NV and SiV centers depends on their local environments. It is essential to understand and control the charge state dynamics for their quantum applications. In this work, we discuss the charge state dynamics of NV and SiV centers under high-voltage nanosecond pulse discharges. The NV and SiV centers coexist in the diamond crystal. The high-voltage pulses enable manipulating the charge states efficiently. These voltage-induced changes in charge states are probed by their photoluminescence spectral analysis. The analysis result from the present experiment shows that the high-voltage nanosecond pulses cause shifts of the chemical potential and can convert the charge states of NV and SiV centers with the transition rates of ∼MHz. This result also indicates that the major population of the SiV centers in the sample is the doubly negatively charged state (SiV2−), which is often overlooked because of its non-fluorescent and non-magnetic nature. This demonstration paves a path for a method of rapid manipulation of the NV and SiV charge states in the future.
Mitigating the Transition of SiV− in Diamond to an Optically Dark State
Negatively charged silicon vacancy centers in diamond (SiV−) are promising for quantum photonic technologies. However, when subject to resonant optical excitation, they can inadvertently transfer into a zero-spin optically dark state. We show that this unwanted change of charge state can be quickly reversed by the resonant laser itself in combination with static electric fields. By defining interdigitated metallic contacts on the diamond surface, we increase the steady-state SiV− photoluminescence under resonant excitation by a factor ≥3 for most emitters, making it practically constant for certain individual emitters. We electrically activate single \sivs near the positively biased electrode, which are entirely dark without applying local electric fields. Using time-resolved 3-color experiments, we show that the resonant laser not only excites the SiV−, but also creates free holes that convert SiV2− to SiV− on a timescale of milliseconds. Through analysis of several individual emitters, our results show that the degree of electrical charge state controllability differs between individual emitters, indicating that their local environment plays a key role. Our proposed electric-field-based stabilization scheme enhances deterministic charge state control in group-IV color centers and improves its understanding, offering a scalable path toward quantum applications such as entanglement generation and quantum key distribution.
The investigation of optically active point defects in wide-bandgap semiconductors is driven by the development of solid-state quantum technologies. Such atom-like defects are used for the realization of quantum registers and quantum sensors. Reproducible engineering of even well-established defects with predictable properties remains challenging, as the local environment and complex charge dynamics limit their performance and applicability. Furthermore, not all defects are optically accessible, which hinders our ability to study them. Here, we use the photoelectric detection technique to study switching and control of desired double and single charge states of silicon vacancy (SiV) defect in diamond. We demonstrate the first direct imaging of the dark charge state of SiV, which cannot be addressed by optical methods or electron paramagnetic resonance. We discuss a model for SiV charge state conversion involving proximal substitutional nitrogen defects. These findings are important for the charge state control of the entire family of group-IV defects in diamond.
The silicon vacancy (SiV) center in diamond is typically found in three stable charge states, SiV 0, SiV –, and SiV 2–, but studying the processes leading to their formation is challenging, especially at room temperature, due to their starkly different photoluminescence rates. Here, we use confocal fluorescence microscopy to activate and probe charge interconversion between all three charge states under ambient conditions. In particular, we witness the formation of SiV 0 via the two-step capture of diffusing, photogenerated holes, a process we expose both through direct SiV 0 fluorescence measurements at low temperatures and confocal microscopy observations in the presence of externally applied electric fields. In addition, we show that continuous red illumination induces the converse process, first transforming SiV 0 into SiV – and then into SiV 2– . Our results shed light on the charge dynamics of SiV and promise opportunities for nanoscale sensing and quantum information processing.
The charge dynamics of silicon-vacancy (SiV) centers have been investigated for the first time in high-pressure high-temperature nanodiamonds (NDs) with varying concentrations of substitutional nitrogen (Ns). We demonstrate a controlled sixfold enhancement of SiV- photoluminescence (PL) under dual-color excitation, consisting of strong red (~660 nm) illumination combined with weak green (~530 nm) excitation. The measured dependencies of SiV- PL lifetime and intensity on excitation wavelength, together with the enhancement dependence on Ns concentration in the studied nanodiamonds, provide unambiguous evidence of the involvement of donor nitrogen in SiV-emission dynamics. Saturation curves and second-order PL intensity correlation measurements further indicate suppression of the population of the optically inactive SiV2- state upon the addition of green excitation. These results unlock a practical pathway toward engineering optically-controlled and scalable quantum emitters based on SiV-luminescent diamond nanoparticles.