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ACS Photonics

Fermi Level-Mediated Charge-State Control of Multicolor Diamond Microcrystals Using High-Voltage Pulses

Sina Ilkhani, Helen Highland, Yifan Song, Sizhe Weng, Ehsan Shamsi, Shunki Nakamura, Susumu Takahashi, Stephen B. Cronin

Published Apr 3, 2026• 0 citations
Publisher

Abstract

Silicon-vacancy (SiV – ) centers in diamond exhibit narrow optical transitions and favorable photophysical properties for quantum photonics and sensing. In microdiamonds, however, electrical control of color-center charge states remains challenging due to their small size, surface- and interface-dominated electronic structure, and the lack of reliable electrical contacts. Here, we report a noncontact strategy for electrically modulating microdiamond powders using nanosecond high-voltage pulses applied at kilohertz repetition rates across a hybrid architecture in which microdiamonds are deposited on electrically insulating bulk CVD diamond substrates. Sustained pulse excitation leads to pronounced and reversible suppression of zero-phonon-line emission from SiB, SiV –, and SiV 0 centers under applied voltages up to 10 kV. Voltage-, frequency-, and temperature-dependent measurements indicate that the modulation arises from charge-redistribution-induced shifts of the local Fermi level within the microdiamond layer, which transiently destabilize the emissive negative charge states. Time-resolved PL reveals recovery dynamics on second time scales consistent with trap-assisted re-equilibration of the local Fermi level mediated by surface and interface states. Measurements across multiple substrates confirm that the response is intrinsic to the microdiamonds and exhibits the opposite polarity to the voltage-enhanced SiV – emission reported in bulk diamonds. This hybrid diamond platform establishes a scalable route to charge redistribution modulation control of nanoscale color centers, providing a versatile framework for probing charge-state dynamics in surface-dominated quantum nanomaterials.

DOI
10.1021/acsphotonics.5c03094

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Silicon-vacancy (SiV – ) centers in diamond exhibit narrow optical transitions and favorable photophysical properties for quantum photonics and sensing. In microdiamonds, however, electrical control of color-center charge states remains challenging due to their small size, surface- and interface-dominated electronic structure, and the lack of reliable electrical contacts. Here, we report a noncontact strategy for electrically modulating microdiamond powders using nanosecond high-voltage pulses applied at kilohertz repetition rates across a hybrid architecture in which microdiamonds are deposited on electrically insulating bulk CVD diamond substrates. Sustained pulse excitation leads to pronounced and reversible suppression of zero-phonon-line emission from SiB, SiV –, and SiV 0 centers under applied voltages up to 10 kV. Voltage-, frequency-, and temperature-dependent measurements indicate that the modulation arises from charge-redistribution-induced shifts of the local Fermi level within the microdiamond layer, which transiently destabilize the emissive negative charge states. Time-resolved PL reveals recovery dynamics on second time scales consistent with trap-assisted re-equilibration of the local Fermi level mediated by surface and interface states. Measurements across multiple substrates confirm that the response is intrinsic to the microdiamonds and exhibits the opposite polarity to the voltage-enhanced SiV – emission reported in bulk diamonds. This hybrid diamond platform establishes a scalable route to charge redistribution modulation control of nanoscale color centers, providing a versatile framework for probing charge-state dynamics in surface-dominated quantum nanomaterials.
Silicon-vacancy defects have been identified as a promising optical transition for quantum communications, quantum control, and quantum information processing. In the work presented here, we demonstrate a voltage-controlled mechanism by which the photoluminescent (PL) emission from silicon-vacancy (Si-V) defects in diamond can be modulated. In particular, we can selectively produce emission from the negatively charged state of this defect (i.e., Si-V−), which exhibits narrow (Γ = 4 nm) emission at 738 nm at low laser power. This approach uses high voltage (2–5 kV) nanosecond pulses applied across top and bottom electrodes on a 0.5 mm thick diamond substrate. In the absence of high voltage pulses, we observe no emission at 738 nm. This feature increases monotonically with peak pulse voltage, pulse repetition rate (i.e., frequency), and incident laser intensity. We observe saturation of the PL intensity for pulse voltages above 3.2 kV and frequency above 100 Hz. Based on electrostatic simulations, we estimated the local electric field intensity near the tip of the Cu electrode to be 2.8 ×106 V/cm at these voltages. However, as a function of laser power, we observe a linear dependence of PL intensity without saturation. These saturating and non-saturating behaviors provide important insight into the voltage-induced charging mechanisms and kinetics associated with this process.
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\ge3≥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−^{2-}2− 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 silicon-vacancy (SiV) color center in diamond has recently emerged as a promising qubit for quantum photonics. However, the electrical control and excitation of the SiV centers are challenging due to the low density of free carriers in doped diamond. Here, we realize electrical excitation of SiV centers in a single-crystal diamond membrane, which is promising for scalable photonic architectures. We further demonstrate electrical switching of the charge states of the SiV centers by applying a forward bias voltage to the fabricated diamond-membrane devices and identify the position of the SiV−/SiV0 charge transition level. Our findings provide a perspective toward electrical triggering of color centers in diamond and accelerate the development of scalable quantum nanophotonic technologies.
ABSTRACT Defect and impurity centers in diamond can exist in multiple charge states. A notable example is a negatively and neutrally charged nitrogen‐vacancy center in diamond, whose optical and spin properties are very different. Recent DFT studies show that an energetically favorable charge state can be controlled by adjusting the chemical potential of the diamond sample, which often requires significant materials engineering. This study presents an alternative approach for the control of charge states with the use of nanosecond high‐voltage pulse discharges. We demonstrate the control of silicon‐vacancy (SiV) centers in diamond. Using time‐resolved photoluminescence (PL) spectroscopy measurement of the SiV centers with the application of nanosecond high‐voltage pulses, we show the emergence of the negatively charged SiV − state. We also employ the time‐resolved PL measurements and show that the population of the induced SiV − charge state decays exponentially, and the lifetime of the charge state is determined by 200–1100 ms. The observed long‐lived charge state is potentially useful for applications based on the SiV − center. This method also paved the way to access various charge states of defect and impurity centers in diamond and wide‐bandgap semiconductors.
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.