Centers In Nanodiamonds Research Articles

Probing Abrikosov vortices in niobium with single nitrogen-vacancy centers in nanodiamonds

Abrikosov vortices play a fundamental role in the magnetic and electric properties of superconductors. The study of their pinning forces is essential to better understand the stability of vortex lattices, with the aim of increasing critical currents in superconductors. However, the study of vortices is challenging because of their nanometric sizes and the large variation in the pinning forces. In this Letter, we use a single nitrogen-vacancy center in a nanodiamond as a nanoscale magneto sensor to locally probe single vortices and their pinning effects in a thin niobium film. This simple, far-field optical approach also offers the possibility of manipulating a single spin with a single flux quantum.

Efficient coupling of single photons from chromium-vacancy centers in nanodiamonds into end-to-end aligned optical nanowires

Abstract We report a numerical simulation on the coupling of chromium-vacancy centers in nanodiamond (CrV-ND) with end-to-end aligned optical nanowires (ONWs) structure. The structure is designed using finite-difference time-domain simulations to maximize the bidirectional coupling of spontaneous emission from a CrV-ND into ONW-guided modes. We systematically analyze the dependence of spontaneous emission characteristics on the ONW and CrV-ND dimension, quantum emitter (QE) position, and polarization. We show that coupling efficiency as high as 62% can be achieved into the guided modes from a CrV-ND placed at the center of ONWs, which is twice as compared to a CrV-ND placed on an ONW surface. The degree of polarization of single photons from CrV-ND is also estimated to be as high as 64%. This simple device can be reconfigured for various QEs. This present fiber inline platform may open new avenues in quantum photonics.

Probing the electronic ground state of the nitrogen-vacancy center in nanodiamonds at room temperature

The color centers in diamonds are promising candidates in the context of quantum information science, quantum computation, and spin-based quantum sensors due to their spin-dependent optical transitions. The manipulation and optical readout of electronic spin state is measured using a technique known as optically detected magnetic resonance (ODMR). Here, we discuss the indigenous development of ODMR setup to coherently manipulate and precise readout of spin state of nitrogen-vacancy centers (NV) in nanodiamond at room-temperature. The study involves the confocal mapping of an ensemble of NV centers to measure spin state-dependent optical transition by applying an optical excitation and microwave field simultaneously. The spin state control appears as a dip at 2.87 GHz in the measured emission intensity spectra as a function of microwave frequency. An ODMR contrast of 3.4 % is achieved at the NV center emission maximum of 660 nm and an inhomogeneous dephasing time of 0.03 microseconds. We find an inherent small split in the ODMR dip which is induced by local strain in nanodiamonds. The split becomes stronger while applying an external magnetic field, which forms the basis of NV center-based magnetometry. The results are useful for spin-based microwave-optical quantum transducers, quantum sensing, and quantum memory devices.

Evaluation of single silicon vacancy centers in nanodiamonds created by ion implantation at cryogenic temperatures

Abstract Silicon vacancy (SiV) centers in diamonds have attracted much attention because of their stability and narrow emission linewidth, and are promising for applications in quantum information technology. SiV-center-encapsulated nanodiamonds have also attracted much attention because of their potential to be coupled to various photonic devices. One efficient way to fabricate nanodiamonds that contain SiV centers is Si ion implantation into nanodiamonds. However, the evaluation of a single SiV center in a nanodiamond produced by this method at low temperatures has not been performed. In this study, we report on the optical properties of a single SiV center in a nanodiamond produced by ion implantation at cryogenic temperatures. The emission spectrum from a single SiV center ( g 2 ( 0 ) = 0.19 ) was observed with four distinct fine splittings of the zero-phonon line (ZPL) at 4 K. At an excitation power of 50 μ W, the full width at half maximum of the ZPL reached the spectrometer resolution limit (0.09 nm). The temperature dependence of the emission peak is consistent with that of the emission coming from an SiV center under high strain. The results obtained in this work suggest that nanodiamonds containing single SiV centers formed using this method will be an important building block for the realization of quantum information applications.

Thermoelectric measurements of nanomaterials by nanodiamond quantum thermometry

In this study, the Seebeck coefficient of a single-walled carbon nanotube (SWCNT) was evaluated using a nitrogen vacancy center in nanodiamonds as a thermometer. A temperature gradient was established across the SWCNT, and the temperatures of the nanodiamonds on the electrodes, along with the electromotive force between these electrodes, were measured. The Seebeck coefficient for a metallic SWCNT was determined to be 14.0 ± 1.1 μV K−1, which is consistent with results reported in previous studies. This methodology offers a promising approach for evaluating the thermoelectric properties of various nanomaterials.

Spatially Resolved Quantum Sensing with High-Density Bubble-Printed Nanodiamonds.

Nitrogen-vacancy (NV-) centers in nanodiamonds have emerged as a versatile platform for a wide range of applications, including bioimaging, photonics, and quantum sensing. However, the widespread adoption of nanodiamonds in practical applications has been hindered by the challenges associated with patterning them into high-resolution features with sufficient throughput. In this work, we overcome these limitations by introducing a direct laser-writing bubble printing technique that enables the precise fabrication of two-dimensional nanodiamond patterns. The printed nanodiamonds exhibit a high packing density and strong photoluminescence emission, as well as robust optically detected magnetic resonance (ODMR) signals. We further harness the spatially resolved ODMR of the nanodiamond patterns to demonstrate the mapping of two-dimensional temperature gradients using high frame rate widefield lock-in fluorescence imaging. This capability paves the way for integrating nanodiamond-based quantum sensors into practical devices and systems, opening new possibilities for applications involving high-resolution thermal imaging and biosensing.

Creation, Control, and Modeling of NV Centers in Nanodiamonds

AbstractSensing based on Nitrogen‐Vacancy (NV) centers in nanodiamonds (NDs) represents a potentially groundbreaking technology with broad applications. Nevertheless, the optimization of their quantum‐optical properties is still a challenging issue. The present work aims at enhancing and controlling NV centers optical properties in NDs by combining their surface chemistry tuning and proton beam irradiation. Systematic thermal oxidations are carried out to study the evolution of surface chemical groups (IR spectroscopy), as well as their influence on optical properties (photoluminescence spectroscopy, PL decay measurements). Proton irradiation is performed by exploring a wide range of fluences (1014 – 1017 cm−2) in order to precisely control the amount of NV centers, thus defining the conditions that maximize their creation and emission intensity. In addition, NV centers charge state control is achieved by assessing NV−/NV0 ratio upon different surface termination tuning and NV centers amount. Finally, a novel predictive mathematical model is developed, allowing for the evaluation of the efficiencies of the formation of both NV− and NV0. Although the model is tested in the specific case study with proton irradiated NDs, it offers a broad applicability, thus representing a key landmark in the prediction of the outcome of ion‐beam‐based color centers generation in diamond.

Near-zero-field microwave-free magnetometry with nitrogen-vacancy centers in nanodiamonds

We study the fluorescence of nanodiamond ensembles as a function of static external magnetic field and observe characteristic dip features close to the zero field with potential for magnetometry applications. We analyze the dependence of the feature’s width and the contrast of the feature on the size of the diamond (in the range 30 nm–3000 nm) and on the strength of a bias magnetic field applied transversely to the field being scanned. We also perform optically detected magnetic resonance (ODMR) measurements to quantify the strain splitting of the zero-field ODMR resonance across various nanodiamond sizes and compare it with the width and contrast measurements of the zero-field fluorescence features for both nanodiamonds and bulk samples. The observed properties provide compelling evidence of cross-relaxation effects in the NV system occurring close to zero magnetic fields. Finally, the potential of this technique for use in practical magnetometry is discussed.

Raman peak shift and broadening in crystalline nanoparticles with lattice impurities

The effect of point-like lattice impurities on nanoparticle Raman spectra is studied using both numerical and analytical methods. Particular cases of replacement atoms of various masses, vacancies, and disorder in interatomic bonds are considered. It is shown that the disorder leads not only to the broadening of optical phonon lines but also to the shift of the corresponding Raman peak. The latter can be either positive (i.e., blueshift) or negative (redshift) depending on the type of impurities. Thus there is an additional contribution to the well-known redshift that occurs due to the size-quantization (confinement) effect. Considering nanometer-sized diamond particles as a representative example, we show that the broadening and the shift are, as a rule, of the same order of magnitude. The results are discussed in the framework of the self-consistent T-matrix approach. It is argued that both effects should be considered for accurate treatment of experimental Raman spectra. Simple recipes to do so are formulated for several important cases including NV centers in nanodiamonds.

Surface optimization of nanodiamonds using non-thermal plasma

Sensitive local monitoring of intracellular processes by quantum sensing utilizing nitrogen-vacancy (NV) centers in nanodiamonds (NDs), would greatly advance cell biology and medicine. However, NDs still fall behind in sensitivity compared to bulk diamond because of their much shorter NV relaxation times. As suggested in theoretical studies, prolongation of NV relaxation times should be achievable by surface optimization creating mixed H/O surface termination consisting of hydrogen atoms, hydroxyl groups, and C–O–C ether bridges. Here we target such chemistry by employing a non-thermal plasma (NTP) in a point-to-plain discharge configuration in aqueous solution. We have devised a set of experiments with different types of nanodiamond samples (of HPHT or detonation origin and with an H- or O-terminated surface) and four working gases (air, O2, He, and H2). Using FTIR, we have found that NTP modification induces a relative increase of O–H and C–H bonds with respect to CO bonds. We have observed the biggest changes in FTIR spectra and the greatest decrease in zeta potential with oxidized NDs (both detonation and HPHT) and hydrogen as the working gas. NV electron spin relaxation times of thus modified HPHT NDs indicate an improvement of the T1 time by ∼17%–∼29% and the T2 time prolongation of 40%.

Sensing the Spin State of Room-Temperature Switchable Cyanometallate Frameworks with Nitrogen-Vacancy Centers in Nanodiamonds.

Room-temperature magnetically switchable materials play a vital role in current and upcoming quantum technologies, such as spintronics, molecular switches, and data storage devices. The increasing miniaturization of device architectures produces a need to develop analytical tools capable of precisely probing spin information at the single-particle level. In this work, we demonstrate a methodology using negatively charged nitrogen vacancies (NV-) in fluorescent nanodiamond (FND) particles to probe the magnetic switching of a spin crossover (SCO) metal-organic framework (MOF), [Fe(1,6-naphthyridine)2(Ag(CN)2)2] material (1), and a single-molecule photomagnet [X(18-crown-6)(H2O)3]Fe(CN)6·2H2O, where X = Eu and Dy (materials 2a and 2b, respectively), in response to heat, light, and electron beam exposure. We employ correlative light-electron microscopy using transmission electron microscopy (TEM) finder grids to accurately image and sense spin-spin interacting particles down to the single-particle level. We used surface-sensitive optically detected magnetic resonance (ODMR) and magnetic modulation (MM) of FND photoluminescence (PL) to sense spins to a distance of ca. 10-30 nm. We show that ODMR and MM sensing was not sensitive to the temperature-induced SCO of FeII in 1 as formation of paramagnetic FeIII through surface oxidation (detected by X-ray photoelectron spectroscopy) on heating obscured the signal of bulk SCO switching. We found that proximal FNDs could effectively sense the chemical transformations induced by the 200 keV electron beam in 1, namely, AgI → Ag0 and FeII → FeIII. However, transformations induced by the electron beam are irreversible as they substantially disrupt the structure of MOF particles. Finally, we demonstrate NV- sensing of reversible photomagnetic switching, FeIII + (18-crown-6) ⇆ FeII + (18-crown-6)+ •, triggered in 2a and 2b by 405 nm light. The photoredox process of 2a and 2b proved to be the best candidate for room-temperature single-particle magnetic switching utilizing FNDs as a sensor, which could have applications into next-generation quantum technologies.

Enhancement of dual zero phonon line emissions in nanodiamonds using quasiperiodic photonic structures.

Color centers in nanodiamonds (NDs) have been largely explored by coupling to a photonic structured matrix (PSM) to amplify visible range emission features, enhancing their use in quantum technologies. Here, we study the emission enhancement of dual near-infrared zero phonon line (ZPL) emission from silicon-boron (SiB) and silicon-vacancy (SiV-) centers in NDs using a spontaneously emerged low index-contrast quasiperiodic PSM, having micron-scale air pores. An intensity enhancement factor of 6.15 for SiV- and 7.8 for SiB ZPLs is attained for the PSM sample compared to a control sample. We find Purcell enhancement of 2.77 times for the PSM sample using spatial-dependent decay rate measurements, supported by localized field intensity confinement in the sample. Such cavity-like emission enhancement and lifetime reduction are enabled by an in-plane order-disorder scattering in the PSM sample substantiated by pump-dependent emission measurements. The results put forward a facile approach to tailor the near-infrared dual ZPL emission from NDs using nanophotonic structures.

Heterogeneous Integration of Solid-State Quantum Systems with a Foundry Photonics Platform.

Diamond color centers are promising optically addressable solid-state spins that can be matter-qubits, mediate deterministic interaction between photons, and act as single photon emitters. Useful quantum computers will comprise millions of logical qubits. To become useful in constructing quantum computers, spin-photon interfaces must, therefore, become scalable and be compatible with mass-manufacturable photonics and electronics. Here, we demonstrate the heterogeneous integration of NV centers in nanodiamond with low-fluorescence silicon nitride photonics from a standard 180 nm CMOS foundry process. Nanodiamonds are positioned over predefined sites in a regular array on a waveguide in a single postprocessing step. Using an array of optical fibers, we excite NV centers selectively from an array of six integrated nanodiamond sites and collect the photoluminescence (PL) in each case into waveguide circuitry on-chip. We verify single photon emission by an on-chip Hanbury Brown and Twiss cross-correlation measurement, which is a key characterization experiment otherwise typically performed routinely with discrete optics. Our work opens up a simple and effective route to simultaneously address large arrays of individual optically active spins at scale, without requiring discrete bulk optical setups. This is enabled by the heterogeneous integration of NV center nanodiamonds with CMOS photonics.

Atomically Precise Detection and Manipulation of Nitrogen-Vacancy Centers in Nanodiamonds.

Nitrogen-vacancy (NV) centers in nanodiamonds are a promising quantum communication system offering robust and discrete single photon emission, but a more thorough understanding of properties of the NV centers is critical for real world implementation in functional devices. The first step to understanding how factors such as surface, depth, and charge state affect NV center properties is to directly characterize these defects on the atomic scale. Here we use Angstrom-resolution scanning transmission electron microscopy (STEM) to identify a single NV center in a ∼4 nm natural nanodiamond through simultaneous acquisition of electron energy loss and energy dispersive X-ray spectra, which provide a characteristic NV center peak and a nitrogen peak, respectively. In addition, we identify NV centers in larger, ∼15 nm synthetic nanodiamonds, although without the single-defect resolution afforded by the lower background of the smaller natural nanodiamonds. We have further demonstrated the potential to directly position these technologically relevant defects at the atomic scale using the scanning electron beam to "herd" NV centers and nitrogen atoms across their host nanodiamonds.

Control of photoluminescence of nitrogen-vacancy centers embedded in diamond nanoparticles coupled to silicon nanoantennas

The development of nanophotonics systems for the manipulation of luminescent properties of single quantum emitters is essential for quantum communication and computing. Dielectric nanosystems enable various opportunities for light control through inherent electric and magnetic resonances; however, their full potential has not yet been discovered. Here, emission properties of nitrogen-vacancy (NV) centers in nanodiamonds placed in the near-field zone of silicon nanoresonators are investigated. It is demonstrated experimentally that the spontaneous emission rate of single NV centers in 50 nm nanodiamonds can be modified by their coupling to spherical nanoantennas, reducing the mode of the lifetime distribution by ≈2 times from 16 to 9 ns. It is also shown that the collected intensity of photoluminescence emission from multiple NV centers in a 150 nm nanodiamond coupled to a cylindrical nanoantenna is increased by more than 50% compared to the intensity from the same nanodiamond on a bare substrate.

Fabrication of single color centers in sub-50 nm nanodiamonds using ion implantation

Abstract Diamond color centers have been widely studied in the field of quantum optics. The negatively charged silicon vacancy (SiV−) center exhibits a narrow emission linewidth at the wavelength of 738 nm, a high Debye–Waller factor, and unique spin properties, making it a promising emitter for quantum information technologies, biological imaging, and sensing. In particular, nanodiamond (ND)-based SiV− centers can be heterogeneously integrated with plasmonic and photonic nanostructures and serve as in vivo biomarkers and intracellular thermometers. Out of all methods to produce NDs with SiV− centers, ion implantation offers the unique potential to create controllable numbers of color centers in preselected individual NDs. However, the formation of single color centers in NDs with this technique has not been realized. We report the creation of single SiV− centers featuring stable high-purity single-photon emission through Si implantation into NDs with an average size of ∼20 nm. We observe room temperature emission, with zero-phonon line wavelengths in the range of 730–800 nm and linewidths below 10 nm. Our results offer new opportunities for the controlled production of group-IV diamond color centers with applications in quantum photonics, sensing, and biomedicine.

Two-Photon Excitation of Silicon-Vacancy Centers in Nanodiamonds for All-Optical Thermometry with a Noise Floor of 6.6 mK·Hz–1/2

In this paper, we introduce ultrasensitive all-optical nanothermometry using high figure-of-merit nanodiamonds with silicon-vacancy (SiV) centers. In contrast to the commonly used single-photon process, we have adopted a two-photon approach to achieve efficient excitation of SiV centers in nanodiamonds. Based on the developed intensity-projected scheme, we have experimentally achieved a noise floor of 6.6 mK·Hz–1/2 using nanodiamonds. This serves as a new record of temperature resolution in the relevant field. Particularly, this simplified method allows us to reflect the temperature-induced spectral shift without wavelength scanning via a spectrometer. Furthermore, we demonstrate that the two-photon excitation of SiV centers has been thermally activated, as indicated by an elevated fluorescence intensity accompanied by a temperature increase. Our findings offer an opportunity for harnessing SiV-based nanothermometry in an easy-to-use manner and open the road for the development of practical applications in complicated environments such as living cells.

Люминесцентные свойства индивидуальных центров "кремний-вакансия" в CVD-наноалмазах, выращенных на различных подложках

The application of the technique of resonant excitation of photoluminescence at low temperatures using a narrow-band tunable laser significantly expands the possibilities of spectral investigation of individual luminescent centers in nanodiamonds, even in conditions of high concentrations of such centers. In this paper, a comparative analysis of the spectral characteristics of individual Silicon-Vacancy (SiV) centers in nanodiamonds grown with a spontaneous nucleation technique on germanium and silicon substrates is carried out. Studied diamond nanoparticles have a characteristic size of 300 nm and contain large ensembles of SiV centers. It was found that during the transition from silicon substrates, which are traditionally used in the CVD synthesis of diamonds, to germanium substrates, the spectral characteristics of the photoluminescence of SiV centers almost do not change.

Effectively enhancing silicon-vacancy emission in a hybrid diamond-in-pit microstructure

Solid-state photon emitters at room temperature appear to be promising candidates for a variety of nanophotonic applications. In this regard, coupling photon emitters with various optical cavities providing pronounced directivity, high photoexcitation and emission rates is extremely desirable. Here, we introduce the novel concept of deterministically coupling color centers in nanodiamonds (NDs) with gold nanopits. We show that in this case, emission of silicon-vacancy (SiV−) centers at the zero-phonon line can exceed that of a ND on a gold surface by a factor of 62. The obtained results reveal an effective pumping of the SiV-centers in NDs along with the active switching of the SiV-centers from the dark to the bright state by plasmon mode that opens the way to design controllable resonance systems with diamond-based photonic emitters.

Optical properties of SiV and GeV color centers in nanodiamonds under hydrostatic pressures up to 180 GPa

The silicon-vacancy (SiV) and germanium-vacancy (GeV) centers in diamond have a sharp photoluminescence with high brightness. In this work, the photoluminescence of these centers is measured up to 180 GPa using nanodiamonds integrated in a diamond anvil cell. The results show blueshifts in the mean emission energy determined by the atomic radii of the impurity. The agreement with $a\phantom{\rule{0}{0ex}}b$ $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ calculations based on the lattice compression of diamond demonstrates the potential of these centers for sensing under extreme pressure conditions.