Coherent communication over mesoscale distances is a necessary condition for the application of solid-state spin qubits to scalable quantum information processing. Among other routes under study, one possibility entails the generation of magnetostatic surface spin waves (MSSW) dipolarly coupled to shallow paramagnetic defects in wide-bandgap semiconductors. As an initial step in this direction, here we make use of room-temperature MSSWs to mediate the interaction between the microwave field from an antenna and the spin of a nitrogen-vacancy (NV) center in diamond. We show that this transport spans distances exceeding 3 mm, a manifestation of the MSSW robustness and long diffusion length. Using the NV spin as a local sensor, we find that the MSSW amplitude grows linearly with the applied microwave power, suggesting this approach could be extended to amplify the signal from neighboring spin qubits by several orders of magnitude.
Photochromism in single nitrogen-vacancy optical centers in diamond is demonstrated. Time-resolved optical spectroscopy shows that intense irradiation at 514 nm switches the nitrogen-vacancy defects to the negative form. This defect state relaxes back to the neutral form under dark conditions. Temporal anticorrelation of photons emitted by the different charge states of the optical center unambiguously indicates that the nitrogen-vacancy defect accounts for both 575 nm and 638 nm emission bands. Possible mechanism of photochromism involving nitrogen donors is discussed.
The negatively charged nitrogen-vacancy defect (NV)$^-$ in diamond has attracted much attention in recent years in qubit and biological applications. The negative charge is donated from nearby nitrogen donors that could limit or stem the successful application of (NV)$^-$. In this Letter, we unambiguously identify the \emph{neutral} nitrogen-vacancy defect (NV$^0$) by \emph{ab initio} supercell calculations. Our analysis shows that i) the spin state can be \emph{selectively} occupied optically, ii) the electron spin state can be manipulated by time-varying magnetic field, and iii) the spin sta…
Symmetry considerations are used in presenting a model of the electronic structure and the associated dynamics of the nitrogen-vacancy center in diamond. The model accounts for the occurrence of optically induced spin polarization, for the change of emission level with spin polarization and for new measurements of transient emission. The rate constants given are in variance to those reported previously.
We investigated the effect of fluorine-terminated diamond surface on the charged state of shallow nitrogen vacancy defect centers (NVs). Fluorination is achieved with CF4 plasma and the surface chemistry is confirmed with x-ray photoemission spectroscopy. Photoluminescence of these ensemble NVs reveal that fluorine-treated surfaces lead to a higher negatively charged nitrogen vacancy (NV-) population than oxygen-terminated surfaces. Using surface chemistry to control NV charges, in particular increasing the density of NV- centers, is an important step towards improving the optical and spin pro…
Optical coupling of an ensemble of silicon-vacancy (SiV) centers to single-crystal diamond microdisk cavities is demonstrated. The cavities are fabricated from a single-crystal diamond membrane generated by ion implantation and, electrochemical liftoff followed by homo-epitaxial overgrowth. Whispering gallery modes which spectrally overlap with the zero-phonon line (ZPL) of the SiV centers and exhibit quality factors ~2200 are measured. Lifetime reduction from 1.8 ns to 1.48 ns is observed from SiV centers in the cavity compared to those in the membrane outside the cavity. These results are pi…
The conversion of neutral nitrogen-vacancy centers to negatively charged nitrogen-vacancy centers is demonstrated for centers created by ion implantation and annealing in high-purity diamond. Conversion occurs with surface exposure to an oxygen atmosphere at 465 C. The spectral properties of the charge-converted centers are investigated. Charge state control of nitrogen-vacancy centers close to the diamond surface is an important step toward the integration of these centers into devices for quantum information and magnetic sensing applications.
The negatively-charged silicon-vacancy (SiV$^-$) center in diamond is a promising single photon source for quantum communications and information processing. However, the center's implementation in such quantum technologies is hindered by contention surrounding its fundamental properties. Here we present optical polarization measurements of single centers in bulk diamond that resolve this state of contention and establish that the center has a $\langle111\rangle$ aligned split-vacancy structure with $D_{3d}$ symmetry. Furthermore, we identify an additional electronic level and evidence for the…
We present high-resolution, all-optical thermometry based on ensembles of GeV color center in diamond. Due to the unique properties of diamond, an all-optical approach using this method opens a way to produce non-invasive, back-action-free temperature measurements in a wide range of temperatures, from a few Kelvin to 1100 Kelvin.
We show that the orientation of nitrogen-vacancy (NV) defects in diamond can be efficiently controlled through chemical vapor deposition (CVD) growth on a (111)-oriented diamond substrate. More precisely, we demonstrate that spontaneously generated NV defects are oriented with a ~ 97 % probability along the [111] axis, corresponding to the most appealing orientation among the four possible crystallographic axes. Such a nearly perfect preferential orientation is explained by analyzing the diamond growth mechanism on a (111)-oriented substrate and could be extended to other types of defects. Thi…
We determine and analyze the charge and spin density distributions of nitrogen-vacancy (N-V) center in diamond for both the ground and excited states by \emph{ab initio} supercell calculations. We show that the hyperfine tensor of $^{15}$N nuclear spin is negative and strongly anisotropic in the excited state, in contrast to previous models used extensively to explain electron spin resonance measurements. In addition, we detect a significant redistribution of the spin density due to excitation that has serious implications for the quantum register applications of N-V center.
Chemical-Vapor-Deposition (CVD) diamond films were prepared using a variation of nitrogen addition into the gas source admixture by a direct current CVD method. The influence of nitrogen addition on the crystallographic texture and grain shape evolution in heteroepitaxial polycrystalline diamond films was investigated using high-resolution electron backscattering diffraction (HR-EBSD) and X-ray diffraction (XRD). The analysis reveals that an addition of 1.5% N2 to the CH4 gas flow leads to a strong enhancement of a {110} fiber texture. The phenomenon is discussed in terms of a competitive grow…
An ensemble of silicon vacancy centers in diamond (\ce{SiV-}) is probed using two coherent spectroscopy techniques. Two main distinct families of \ce{SiV-} centers are identified using multidimensional coherent spectroscopy, and these families are paired with two orientation groups by comparing spectra from different linear polarizations of the incident laser. By tracking the peak centers in the measured spectra, the full diamond strain tensor is calculated local to the laser spot. Such measurements are made at multiple points on the sample surface and variations in the strain tensor are obser…
Although chemical vapor deposition (CVD) is one of the preferred routes to synthetic diamond crystals, a full knowledge of the point defects produced during growth is still incomplete. Here we exploit the charge and spin properties of nitrogen-vacancy (NV) centers in type-1b CVD diamond to expose an optically and magnetically dark point defect, so far virtually unnoticed despite an abundance comparable to (if not greater than) that of substitutional nitrogen. Indirectly-detected photo-luminescence spectroscopy indicates a donor state 1.6 eV above the valence band, although the defect's microsc…
It is suggested that the substitutional nitrogen in diamonds bonded to three of the surrounding carbon atoms instead of four. This proposed electron configuration of the defect is deduced from previous experiments and theoretical considerations. Notably, the 1344 cm-1 band, characteristics of the substitutional Nitrogen, is independent of the isotopic change of Nitrogen but depend on the isotopic change of Carbon. The well established NV centre should not be stable if Nitrogen is bounded to four of the surrounding Carbon. Additional support comes from the substantially bigger size of the singl…
Vacancy-mediated nitrogen diffusion and aggregation via high-fluence electron beam irradiation in HPHT synthesized diamond crystal
National Institute for Materials Science（物质材料研究机构）；University of Tsukuba（筑波大学）；National Institutes for Quantum Science and Technology（量子科学技术研究开发机构）；Tohoku University（东北大学）
This work explores the possibility of increasing the density of negatively charged nitrogen-vacancy centers [NV-] in nanodiamonds using nitrogen-rich type Ib diamond powders as the starting materials. The nanodiamonds (10 - 100 nm in diameters) were prepared by ball-milling of microdiamonds, in which the density of neutral and automatically dispersed nitrogen atoms [N0] was measured by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). A systematic measurement for the fluorescence intensities and lifetimes of the crushed monocrystalline diamonds as a function of [N0] indicate…
Optical and microwave double resonance techniques are used to obtain the excited state structure of single nitrogen-vacancy centers in diamond. The excited state is an orbital doublet and it is shown that it can be split and associated transition strengths varied by external electric fields and by strain. A group theoretical model is developed. It gives a good account of the observations and contributes to an improved understanding of the electronic structure of the center. The findings are important for quantum information processing and other applications of the center.
Nitrogen-vacancy (NV-) color centers in diamond were created by implantation of 7 keV 15N (I = 1/2) ions into type IIa diamond. Optically detected magnetic resonance was employed to measure the hyperfine coupling of the NV- centers. The hyperfine spectrum from 15NV- arising from implanted 15N can be distinguished from 14NV- centers created by native 14N (I = 1) sites. Analysis indicates 1 in 40 implanted 15N atoms give rise to an optically observable 15NV- center. This report ultimately demonstrates a mechanism by which the yield of NV- center formation by nitrogen implantation can be measured…
The split silicon-vacancy defect (SiV) in diamond is an electrically and optically active color center. Recently, it has been shown that this color center is bright and can be detected at the single defect level. In addition, the SiV defect shows a non-zero electronic spin ground state that potentially makes this defect an alternative candidate for quantum optics and metrology applications beside the well-known nitrogen-vacancy color center in diamond. However, the electronic structure of the defect, the nature of optical excitations and other related properties are not well-understood. Here w…
We report the first experimental observation of a doubly-charged defect in diamond, SiV2-, in silicon and nitrogen co-doped samples. We measure spectroscopic signatures we attribute to substitutional silicon in diamond, and identify a silicon-vacancy complex decorated with a nearest-neighbor nitrogen, SiVN, supported by theoretical calculations. Samples containing silicon and nitrogen are shown to be heavily photochromic, with the dominant visible changes due to the loss of SiV0/- and gain in the optically-inactive SiV2-.
Quantum-mechanical ab initio calculations are performed to elucidate the vibrational spectroscopic features of a common irradiation-induced defect in diamond, i.e. the neutral vacancy. Raman spectra are computed analytically through a Coupled-Perturbed-Hartree-Fock/Kohn-Sham approach as a function of both different defect spin states and defect concentration. The experimental Raman features of defective diamond located in the 400-1300 cm-1 spectral range, i.e. below the first-order line of pristine diamond at 1332 cm-1 , are well reproduced, thus corroborating the picture according to which, a…
The nitrogen-vacancy colour centre in diamond is emerging as one of the most important solid-state quantum systems. It has applications to fields including high-precision sensing, quantum computing, single photon communication, metrology, nanoscale magnetic imaging and biosensing. For all of these applications, a high quantum yield of emitted photons is desirable. However, diamond samples engineered to have high densities of nitrogen-vacancy centres show levels of brightness varying significantly within single batches, or even within the same sample. Here we show that nearby nitrogen impuritie…
In this paper, starting from a quantum master equation, we discuss the interaction between two negatively charged Nitrogen-vacancy color centers in diamond via exciton-polaritons propagating in a two-dimensional transition metal dichalcogenide layer in close proximity to a diamond crystal. We focus on the optical 1.945 eV transition and model the Nitrogen-vacancy color centers as two-level (artificial) atoms. We find that the interaction parameters and the energy levels renormalization constants are extremely sensitive to the distance of the Nitrogen-vacancy centers to the transition metal dic…
Electrically driven emission from negatively charged silicon-vacancy, (SiV)- centres in single crystal diamond is demonstrated. The SiV centres were generated using ion implantation into an intrinsic (i) region of a p-i-n single crystal diamond diode. Both electroluminescence and the photoluminescence signals exhibit the typical emission that is attributed to the (SiV)- centres. Under forward and reversed biased PL measurements, no signal from the neutral (SiV)0 defect could be observed. The realization of electrically driven (SiV)- emission is promising for scalable nanophotonics devices empl…
We report on wide-field optically detected magnetic resonance imaging of nitrogen-vacancy centers (NVs) in type IIa polycrystalline diamond. These studies reveal a heterogeneous crystalline environment that produces a varied density of NV centers, including preferential orientation within some individual crystal grains, but preserves long spin coherence times. Using the native NVs as nanoscale sensors, we introduce a 3-dimensional strain imaging technique with high sensitivity ( $< 10^{-5}$ Hz$^{-1/2}$) and diffraction-limited resolution across a wide field of view.
We show a marked reduction in the emission from nitrogen-vacancy (NV) color centers in single crystal diamond due to exposure of the diamond to hydrogen plasmas ranging from 700°C to 1000°C. Significant fluorescence reduction was observed beneath the exposed surface to at least 80mm depth after ~10 minutes, and did not recover after post-annealing in vacuum for seven hours at 1100°C. We attribute the fluorescence reduction to the formation of NVH centers by the plasma induced diffusion of hydrogen. These results have important implications for the formation of nitrogen-vacancy centers for quan…
The localized spin triplet ground state of a nitrogen vacancy (NV) center in diamond can be used in atomic-scale detection of local magnetic fields. Here we present a technique using these defects in diamond to image fields around magnetic structures. We extract the local magnetic field vector by probing resonant transitions of the four fixed tetrahedral NV orientations. In combination with confocal microscopy techniques, we construct a 2-dimensional image of the local magnetic field vectors. Measurements are done in external fields less than 50 G and under ambient conditions.
Experiments show that shallow nitrogen implantations (<10keV) result in a negatively charged nitrogen-vacancy center (NV-) yield of 0.01-0.1%. The most succesful technique for introducing NV- centers in the carbon matrix is ion implantation followed by annealing at 1100K. We investigated the influence of channeling effects during shallow implantation and statistical diffusion using molecular dynamics (MD) and Monte Carlo (MC) approaches. Energy barriers for the diffusion process were calculated using the density functional theory (DFT). Our simulations show a significant difference in the NV y…
Nanodiamond crystals containing single color centers have been grown by chemical vapor deposition (CVD). The fluorescence from individual crystallites was directly correlated with crystallite size using a combined atomic force and scanning confocal fluorescence microscope. Under the conditions employed, the optimal size for single optically active nitrogen-vacancy (NV) center incorporation was measured to be 60 to 70 nm. The findings highlight a strong dependence of NV incorporation on crystal size, particularly with crystals less than 50 nm in size.
The optical transition linewidth and emission polarization of single nitrogen-vacancy (NV) centers are measured from 5 K to room temperature. Inter-excited state population relaxation is shown to broaden the zero-phonon line and both the relaxation and linewidth are found to follow a T^5 dependence for T up to 100 K. This dependence indicates that the dynamic Jahn-Teller effect is the dominant dephasing mechanism for the NV optical transitions at low temperatures.
Nitrogen-vacancy (NV) centers in diamond can be used for nanoscale sensing with atomic resolution and sensitivity; however, it has been observed that their properties degrade as they approach the diamond surface. Here we report that in addition to degraded spin coherence, NV centers within nanometers of the surface can also exhibit decreased fluorescence contrast for optically detected electron spin resonance (OD-ESR). We demonstrate that this decreased OD-ESR contrast arises from charge state dynamics of the NV center, and that it is strongly surface-dependent, indicating that surface enginee…
Diamond and Silicon Carbide (SiC) are promising wide band-gap semiconductors for power electronics, SiC being more mature especially in term of large wafer size (that has reached 200 mm quite recently). Nitrogen impurities are often used in both materials for different purpose: increase the diamond growth rate or induce n-type conductivity in SiC. The determination of the nitrogen content by secondary ion mass spectrometry (SIMS) is a difficult task mainly because nitrogen is an atmospheric element for which direct monitoring of N$^\pm$ ions give no or a weak signal. With our standard diamond …
Nitrogen is frequently included in chemical vapour deposition feed gases to accelerate diamond growth. While there is no consensus for an atomistic mechanism of this effect, existing studies have largely focused on the role of sub-surface nitrogen and nitrogen-based adsorbates. In this work, we demonstrate the catalytic effect of surface-embedded nitrogen in nucleating new layers of (100) diamond. To do so we develop a model of nitrogen overgrowth using density functional theory. Nucleation of new layers occurs through C insertion into a C--C surface dimer. However, we find that C insertion in…
We present a beam-directed chemical technique for controlling the charge states of near-surface luminescence centers in semiconductors. Specifically, we fluorinate the surface of H-terminated diamond by electron beam irradiation in the presence of NF3 vapor. The fluorination treatment acts as a local chemical switch that alters the charge state of nitrogen-vacancy luminescence centers from the neutral to the negative state. The electron beam fluorination process is highly localized and can be used to control the emission spectrum of individual nanodiamonds and surface regions scanned by the el…
We introduce a process for the fabrication of high quality, spatially isolated nano-diamonds on iridium via microwave plasma assisted CVD-growth. We perform spectroscopy of single silicon-vacancy (SiV)-centres produced during the growth of the nano-diamonds. The colour centres exhibit extraordinary narrow zero-phonon-lines down to 0.7 nm at room temperature. Single photon count rates up to 4.8 Mcps at saturation make these SiV-centres the brightest diamond based single photon sources to date. We measure for the first time the fine structure of a single SiV-centre thus confirming the atomic com…
Vacancy centers in diamond have proven to be a viable solid-state platform for quantum coherent opto-electronic applications. Among the variety of vacancy centers, silicon-vacancy (SiV) centers have recently attracted much attention as an inversion-symmetric system that is less susceptible to electron-phonon interactions. Nevertheless, phonon-mediated processes still degrade the coherent properties of SiV centers, however characterizing their electron-phonon coupling is extremely challenging due to their weak spectroscopic signatures and remains an open experimental problem. In this paper we t…
Etching experiments were performed that reveal the vertical distribution of optically active nitrogen-vacancy (NV) centers in diamond created in close proximity to a surface through ion implantation and annealing. The NV distribution depends strongly on the native nitrogen concentration, and spectral measurements of the neutral and negatively-charged NV peaks give evidence for electron depletion effects in lower-nitrogen material. The results are important for potential quantum information and magnetometer devices where NV centers must be created in close proximity to a surface for coupling to…
Using microwave-assisted plasma chemical vapour deposition (CVD) a layer of Nitrogen doped ultra-nano-crystalline diamond (N-UNCD) is deposited on top of a non-conducting diamond layer, which itself is situated on a Silicon wafer. This structure is then shaped into Hall-bar devices of various dimensions using optical lithography and dry-etching techniques. The devices' electrical properties are investigated at various temperatures using a cryogen-free dilution refrigerator.
Spin ensembles of nitrogen vacancy (NV) centers in diamond are emerging as powerful spin-based sensors for magnetic, electric and thermal field imaging with high spatial and temporal resolution. Here we characterize the formation of depth-confined NV center ensembles, activated by electron irradiation in diamond layers grown by plasma enhanced chemical vapor deposition with nitrogen co-doping. To do so, we exploit the high magnetic sensitivity of ensembles of NV centers to probe their spin environment as a function of growth and irradiation parameters. We engineer an NV ensemble whose magnetic…
The atomic orbital basis and atomic pseudopotential for electron-ion interaction in framework of density function theory used to calculate C70H84 spin polarized diamond cluster with neutral vacancy. The band gap has been found to be 1.70 eV. The chosen cluster comprises electronic properties depending on thetype of its spin. It could be used as a data transporter. The calculated band gap, density of state and spin properties illustrate how beneficial it could be in spintronic devices.
Exposure to beams of low energy electrons (2 to 30 keV) in a scanning electron microscope locally induces formation of NV-centers without thermal annealing in diamonds that have been implanted with nitrogen ions. We find that non-thermal, electron beam induced NV-formation is about four times less efficient than thermal annealing. But NV-center formation in a consecutive thermal annealing step (800C) following exposure to low energy electrons increases by a factor of up to 1.8 compared to thermal annealing alone. These observations point to reconstruction of nitrogen-vacancy complexes induced …
The nitrogen-vacancy center in diamond is a promising candidate for realizing the spin qubits concept in quantum information. Even though this defect is known for a long time, its electronic structure and other properties have not yet been explored in detail. We study the properties of the nitrogen-vacancy center in diamond through density functional theory within the local spin density approximation, using supercell calculations. While this theory is strictly applicable for ground state properties, we are able to give an estimate for the energy sequence of the excited states of this defect. W…
The silicon-vacancy center in diamond offers attractive opportunities in quantum photonics due to its favorable optical properties and optically addressable electronic spin. Here, we combine both to achieve all-optical coherent control of its spin states. We utilize this method to explore spin dephasing effects in an impurity-rich sample beyond the limit of phonon-induced decoherence: Employing Ramsey and Hahn-echo techniques at 12mK base temperature we identify resonant coupling to a substitutional nitrogen spin bath as the limiting decoherence source for the electron spin.
We investigate the effect of surface termination on the charge state of nitrogen vacancy centers, which have been ion-implanted few nanometers below the surface of diamond. We find that, when changing the surface termination from oxygen to hydrogen, previously stable NV- centers convert into NV0 and, subsequently, into an unknown non-fluorescent state. This effect is found to depend strongly on the implantation dose. Simulations of the electronic band structure confirm the dissappearance of NV- in the vicinity of the hydrogen-terminated surface. The band bending, which induces a p-type surface…
Fluorescent nanodiamonds containing negatively-charged nitrogen-vacancy (NV$^-$) centers are promising for a wide range of applications, such as for sensing, as fluorescence biomarkers, or to hyperpolarize nuclear spins. NV$^-$ centers are formed from substitutional nitrogen (P1 centers) defects and vacancies in the diamond lattice. Maximizing the concentration of NVs is most beneficial, which justifies the search for methods with a high yield of conversion from P1 to NV$^-$. We report here the characterization of surface cleaned fluorescent micro- and nanodiamonds, obtained by irradiation of …
We report depth-resolved photoluminescence measurements of nitrogen-vacancy (NV$^-$) centers formed along the tracks of swift heavy ions (SHIs) in type Ib synthetic single crystal diamonds that had been doped with 100 ppm nitrogen during crystal growth. Analysis of the spectra shows that NV$^-$ centers are formed preferentially within regions where electronic stopping processes dominate and not at the end of the ion range where elastic collisions lead to formation of vacancies and defects. Thermal annealing further increases NV yields after irradiation with SHIs preferentially in regions with …
Single crystal diamond membranes that host optically active emitters are highly attractive components for integrated quantum nanophotonics. In this work we demonstrate bottom-up synthesis of single crystal diamond membranes containing the germanium vacancy (GeV) color centers. We employ a lift-off technique to generate the membranes and perform chemical vapour deposition in a presence of germanium oxide to realize the insitu doping. Finally, we show that these membranes are suitable for engineering of photonic resonators such as microring cavities with quality factors of 1500. The robust and s…
We demonstrate that silicon-vacancy (SiV) centers in diamond can be used to efficiently generate coherent optical photons with excellent spectral properties. We show that these features are due to the inversion symmetry associated with SiV centers, and demonstrate generation of indistinguishable single photons from separate emitters in a Hong-Ou-Mandel (HOM) interference experiment.Prospects for realizing efficient quantum network nodes using SiV centers are discussed.
The controlled creation of color centers in phosphorus-doped (n-type) diamond can facilitate the electronics integration of quantum photonics devices, such as single-photon sources operating upon electrical injection. Silicon vacancy (SiV) color centers are promising candidates, but so far the conditions for single-photon emission in phosphorus-doped diamond have not been investigated. In this study, we create SiV color centers in diamond samples with different phosphorus concentrations and show that the fluorescence background due to doping, nitrogen-impurities and ion implantation induced de…
We present systematic measurements of longitudinal relaxation rates ($1/T_1$) of spin polarization in the ground state of the nitrogen-vacancy (NV$^-$) color center in synthetic diamond as a function of NV$^-$ concentration and magnetic field $B$. NV$^-$ centers were created by irradiating a Type 1b single-crystal diamond along the [100] axis with 200 keV electrons from a transmission electron microscope with varying doses to achieve spots of different NV$^-$ center concentrations. Values of ($1/T_1$) were measured for each spot as a function of $B$.
We characterize a high-density sample of negatively charged silicon-vacancy (SiV$^-$) centers in diamond using collinear optical multidimensional coherent spectroscopy. By comparing the results of complementary signal detection schemes, we identify a hidden population of \ce{SiV^-} centers that is not typically observed in photoluminescence, and which exhibits significant spectral inhomogeneity and extended electronic $T_2$ times. The phenomenon is likely caused by strain, indicating a potential mechanism for controlling electric coherence in color-center-based quantum devices.
The silicon-vacancy centre (SiV) in diamond has interesting vibronic features. We demonstrate that the zero phonon line position can be used to reliably identify the silicon isotope present in a single centre. This is of interest for quantum information applications since only the silicon 29 isotope has nuclear spin. In addition, we demonstrate that the 64 meV line is due to a local vibrational mode of the silicon atom. The presence of a local mode suggests a plausible origin of the isotopic shift of the zero phonon line.
Group-IV color centers in diamond have garnered great interest for their potential as optically active solid-state spin qubits. Future utilization of such emitters requires the development of precise site-controlled emitter generation techniques that are compatible with high-quality nanophotonic devices. This task is more challenging for color centers with large group-IV impurity atoms, which are otherwise promising because of their predicted long spin coherence times without a dilution refrigerator. For example, when applied to the negatively charged tin-vacancy (SnV$^-$) center, conventional…
Color centers in diamond are widely explored for applications in quantum sensing, computing, and networking. Their optical, spin, and charge properties have been extensively studied, while their interactions with itinerant carriers are relatively unexplored. Here we show that NV centers situated within 10 nm of the diamond surface can be converted to the neutral charge state via hole capture. By measuring the hole capture rate, we extract the capture cross section, which is suppressed by proximity to the diamond surface. The distance dependence is consistent with a carrier diffusion model, ind…
The application of imaging techniques based on ensembles of nitrogen-vacancy (NV) sensors in diamond to characterise electrical devices has been proposed, but the compatibility of NV sensing with operational gated devices remains largely unexplored. Here we fabricate graphene field-effect transistors (GFETs) directly on the diamond surface and characterise them via NV microscopy. The current density within the gated graphene is reconstructed from NV magnetometry under both mostly p- and n-type doping, but the exact doping level is found to be affected by the measurements. Additionally, we obse…
Fluorescent nanodiamonds are attracting major attention in the field of bio-sensing and biolabeling. In this work we demonstrate a robust approach to surface functionalize individual nanodiamonds with metal-phenolic networks that enhance the photoluminescence from single nitrogen vacancy (NV) centers. We show that single NV centres in the coated nanodiamonds also exhibit shorter lifetimes, opening another channel for high resolution sensing. We propose that the nanodiamond encapsulation suppresses the non-radiative decay pathways of the NV color centers. Our results provide a versatile and ass…
Individual, luminescent point defects in solids so called color centers are atomic-sized quantum systems enabling sensing and imaging with nanoscale spatial resolution. In this overview, we introduce nanoscale sensing based on individual nitrogen vacancy (NV) centers in diamond. We discuss two central challenges of the field: First, the creation of highly-coherent, shallow NV centers less than 10 nm below the surface of single-crystal diamond. Second, the fabrication of tip-like photonic nanostructures that enable efficient fluorescence collection and can be used for scanning probe imaging bas…
