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arXiv:2610.03150

Self-organized Layered Structures of Nitrogen-Vacancy Centers with Preferential Orientation in Heteroepitaxial Diamond Films

Vadim Lebedev, Alejandro Martínez-Méndez, Jesús Moreno-Meseguer, Jan Engels, Jürgen Weippert, Jan Kustermann, Felix Hoffmann, Javier Prior, Jan Jeske

quant-phcond-mat.mtrl-sciphysics.opticsSubmitted Oct 2, 2026• Announced Oct 5, 2026
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Abstract

Here, we report the fabrication and characterization of single crystal diamond films on a two-inch wafer-scale containing three-dimensional layered structures of negatively charged nitrogen-vacancy color centers (NV$^{-}$). The (100)-oriented layered diamond films were grown by chemical vapor deposition (CVD) to create spatially separated regions of enhanced emission associated with NV$^{-}$ centers. Such localized emission enhancement as well as 2D and 3D arrays of spins could enable close-packed architectures for emerging quantum devices, such as data processors, memory cells, and magnetic sensors. A cyclic sequence of CVD growth and oxygen-plasma etching is employed, resulting in the in-situ formation of layered inverted pyramidal structures with flat $\{$111$\}$ sidewalls. These pits are subsequently overgrown by nitrogen-doped diamond to achieve NV$^{-}$-rich facets with a uniform N-V bond arrangement and improved nitrogen incorporation efficiency.

Comments
5 pages, 6 figures

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Here, we report the fabrication and characterization of single crystal diamond films on a two-inch wafer-scale containing three-dimensional layered structures of negatively charged nitrogen-vacancy color centers (NV−^{-}−). The (100)-oriented layered diamond films were grown by chemical vapor deposition (CVD) to create spatially separated regions of enhanced emission associated with NV−^{-}− centers. Such localized emission enhancement as well as 2D and 3D arrays of spins could enable close-packed architectures for emerging quantum devices, such as data processors, memory cells, and magnetic sensors. A cyclic sequence of CVD growth and oxygen-plasma etching is employed, resulting in the in-situ formation of layered inverted pyramidal structures with flat {\{{111}\}} sidewalls. These pits are subsequently overgrown by nitrogen-doped diamond to achieve NV−^{-}−-rich facets with a uniform N-V bond arrangement and improved nitrogen incorporation efficiency.
The negatively charged nitrogen-vacancy (${\mathrm{NV}}^{\ensuremath{-}}$) center in diamond is an attractive candidate for applications that range from magnetometry to quantum information processing. Here we show that only a fraction of the nitrogen (typically <0.5<0.5<0.5%) incorporated during homoepitaxial diamond growth by chemical vapor deposition (CVD) is in the form of undecorated ${\mathrm{NV}}^{\ensuremath{-}}$ centers. Furthermore, studies on CVD diamond grown on (110)(110)(110)-oriented substrates show a near 100% preferential orientation of NV centers along only the [111][111][111] and [1‾1‾1][\overline{1}\overline{1}1][111] directions, rather than the four possible orientations. The results indicate that NV centers grow in as units, as the diamond is deposited, rather than by migration and association of their components. The NV unit of the ${\mathrm{NVH}}^{\ensuremath{-}}$ is similarly preferentially oriented, but it is not possible to determine whether this defect was formed by H capture at a preferentially aligned NV center or as a complete unit. Reducing the number of NV orientations from four orientations to two orientations should lead to increased optically detected magnetic resonance contrast and thus improved magnetic sensitivity in ensemble-based magnetometry.
Heteroepitaxial chemical vapor deposition is the most promising option to fabricate wafer-scale monocrystalline diamonds for quantum applications. Previously, we demonstrated the feasibility to manufacture functional micrometer-sized pyramids on as-grown heteroepitaxial diamond as well as their quantum optical characteristics. Due to high background signals and microfabrication challenges, these pyramids could not compete with homoepitaxially grown structures. In this study, we overcame these problems with a nominally undoped buffer layer between the heteroepitaxial substrate and the pyramidal microstructure to reduce the signal-to-noise ratio from the substrate on the spin measurements of the nitrogen-vacancy (NV) center. Moreover, the microfabrication was improved to reach a higher angle of the pyramidal side plane, corresponding to the {111} facets. These improvements lead to pyramids on which each facet contains almost purely only one of the four possible NV orientations as shown by optically detected magnetic resonance (ODMR). ODMR shows a very high contrast of 19% without an external magnet and of 13% for a single spin resonance in the presence of a magnetic field. The contrast is more than doubled compared to our previous study. The T2* dephasing time of the NV centers of the samples ranges from 0.02 to 0.16 μs. The P1 center is a single substitutional nitrogen center, and the P1 densities range from 1.8 to 5 ppm.
Silicon has turned from a niche laboratory-scale material into the backbone of modern electronics. Diamond functionalized with color centers could follow a similar path and grow from proof-of-concepts experiments to application-oriented quantum technologies. Quantum sensing, communication, and information processing with color centers has been proven to work in scientific experiments and enhanced sensitivities as well as novel functionalities have been reported. While the first generation of diamond quantum devices relied on color centers formed uncontrolled in natural diamond with a high statistical variation in composition and crystallinity, the situation has changed nowadays. With the emergence of high purity monocrystals and the option for isotopic purification of the carbon matrix, technological progress in materials science on the atomic-scale enabled tailoring the spin properties in diamond. But, since many color centers typically require vacancies to combine with impurities in the carbon lattice via diffusion, the generation of color centers underlies a statistical process providing only little control on the center's final position in the crystal lattice. The negatively charged nitrogen-vacancy (NV−^-−) center is the most studied optically active defect in diamond and exhibits remarkable spin properties and sensing capabilities, even on the nanoscale and at room temperature. The spin properties of NV−^-− centers close to the surface (1\,nm - 30\,nm) have been thoroughly studied and the deeper the spins are located in diamond the less decoherence from surface defects is observed. Creating NV−^-− centers at the surface by nitrogen ion implantation and burying them beneath a thin diamond layer via chemical vapor deposition (CVD) of diamond is reported to enhance the coherence times significantly. By separating the color center generation from controlling the resulting depth by an additional diamond layer, narrow depth profiles can be achieved by reducing the ion energy during implantation. Although the coherence properties improve, many of the implanted NV−^-− center are reported to vanish in the hydrogen-rich plasma of growth CVD chambers. The mechanism responsible for the instability of NV−^-− centers towards the plasma remains unclear, though. One hypothesis is the formation of nitrogen-vacancy-hydrogen centers from diffusing hydrogen and implanted NV−^-− centers but is has not been proven, yet. Here, we demonstrate the fabrication of depth confined NV−^-− centers by combining low energy (1\,keV - 5\,keV) ion implantation and CVD overgrowth. By increasing the thickness of the overgrown layer (6\,nm - 100\,nm) the influence of surface noise is shown to decrease leading to bulk-like coherence properties of up to $450\,\upmu$s (Hahn-echo) and T2∗T_2^*T2∗​ dephasing times around $20\,\upmu$s. Monitoring the NV−^-− density as a function of the overgrowth time, we analyze the kinetics of the passivation in case of implanting ion doses of 1011^{11}11 15^{15}15N +^{+}+/cm2^22 and 1012^{12}12 15^{15}15N +^{+}+/cm2^22. The passivation turns out to occur faster for lower doses offering insights into sub-surface hydrogen diffusion in diamond. Analyzing the spin bath before and after overgrowth reveals a drastic reduction in paramagnetic spins after the CVD process but no NVH−^-− is found around the surviving NV−^-− centers. Checking the chemical composition in overgrown implantation sites with secondary-ion-mass-specrometry (SIMS), however, confirms significant amounts of hydrogen in the 15^{15}15N-implanted layers. Since the concentration found for hydrogen exceeds the one for nitrogen by far, we suggest that diffusing hydrogen interacts also with vacancies forming probably mostly diamagnetic defects. In the last part of this dissertation, NV−^-− centers are generated with sub-nanometer precision below a thin 13^{13}13C-enriched layer for quantum simulation. For fabricating the spin architecture starting from a 12^{12}12C base layer, we overgrow implanted nitrogen with a 13^{13}13C layer and bury the spins beneath a 30\,nm-thick 12^{12}12C capping layer. By measuring the coupling strength between the electron and nuclear spins, we deduce a NV−^-− placement accuracy reaching below one nanometer with respect to the 13^{13}13C-layer. Regarding the spin properties of the electron spins, no reduction in T2T_2T2​ is observed despite of the proximity to the dense 13^{13}13C-bath. As a consequence, the overgrowth of NV−^-− centers is demonstrated as a bottom-up approach to produce buried spin architectures with sharp isotopic transitions and efficient 13^{13}13C-NV−^-− coupling. Together with the potential for bulk-like coherence properties the synergy of implantation and overgrowth is a powerful tool to fabricate reproducible quantum systems with tailored properties and high depth confinement.
Nitrogen-vacancy (NV) centers in chemical-vapor-deposition (CVD) diamond can form preferentially oriented ensembles with high sensing performance and low densities of lattice defects. Thin films of this material are a cornerstone of various imaging modalities. However, nitrogen injection needed to produce such films can transiently drive growth out of equilibrium, generating interfacial strain and spin defects that degrade NV coherence. Here, we investigate this disorder in 12C^{12}\text{C}12C-enriched, preferentially oriented NV layers grown on (111) diamond using two nitrogen-injection procedures, combined with nanometer-scale selective plasma etching and NV spin-coherence measurements. Pulsed nitrogen injection produces a pronounced nitrogen overshoot within a 60--80 nm interfacial region, generating excessive amounts of defects. By contrast, smooth nitrogen delivery through mass flow controllers substantially suppresses interfacial disorder, yielding coherence properties close to the theoretical limit imposed by spin-bath noise. A 50-nm NV layer is used to demonstrate proton nuclear magnetic resonance detection. This work reveals the role of interfacial disorder associated with the nitrogen-doping procedure and provides a route to growing high-quality, thin NV-doped layers for quantum-sensing applications.
Abstract Confocal photoluminescence (PL) microscopy was used to study a distribution of negatively charged nitrogen-vacancy (NV − ) defects within a surface and in a cross section of a homoepitaxial chemical vapor deposition (CVD) diamond layer intentionally grown with a nitrogen concentration close to the solubility limit. A variation in the PL intensity within the whole sample was found to exceed no more than 30% of the intensity maximum. The diamond layers with densely packed NV − arrays are a promising material platform for the design of highly sensitive magnetic field and temperature sensors, as well as for using this material in quantum optics and informatics technologies based on NV − spins.
We investigate native nitrogen vacancy (NV) and silicon vacancy (SiV) color centers in a commercially available, heteroepitaxial, wafer-sized, mm thick, single-crystal diamond. We observe single, native NV centers with a density of roughly 1 NV per μm3 and moderate coherence time (T2 = 5 μs) embedded in an ensemble of SiV centers. Using low temperature luminescence of SiV centers as a probe, we prove the high crystalline quality of the diamond especially close to the growth surface, consistent with a reduced dislocation density. Using ion implantation and plasma etching, we verify the possibility to fabricate nanostructures with shallow color centers rendering our material promising for fabrication of nanoscale sensing devices. As this diamond is available in wafer-sizes up to 100 mm, it offers the opportunity to up-scale diamond-based device fabrication.