The nanolayers and nanomembranes with the 30–300 thickness and the 0.5 ppm NV– center content were produced by 50 keV $${\text{H}}_{2}^{ + }$$ ion implantation in Ib type (111) diamond plates and vacuum or high pressure annealing with subsequent lift-off process. The similar NV– content nanolayers were formed by N+ ion implantation in IIa type (111) diamond plates and similar annealings. 〈111〉 oriented nanopillars were produced on both types of nanolayers using focused ion beam (FIB) with Ga+ 30 keV maskless milling. The unusual optically detected magnetic resonances (ODMRs) were measured in a single nanopillars with a height of 500‒700 nm and of 250 nm in diameter covered by an amorphous a-C:Ga nanolayer in the 0‒20 G magnetic field. They demonstrated both a significant decrease in the gyromagnetic ratio and the quenching of photoluminescence (PL) signal from the NV– centers inclined to the nanopillar axis by the conductive a‑C:Ga nanolayer and stresses created by it. The multistep O2 RIE plasma etching restored the normal ODMR resonance frequencies and intensities for all four NV–center orientations in (111) diamond nanopillars.
The nanolayers and nanomembranes with the 30–300 thickness and the 0.5 ppm NV– center content were produced by 50 keV H2+ ion implantation in Ib type (111) diamond plates and vacuum or high pressure annealing with subsequent lift-off process. The similar NV– content nanolayers were formed by N+ ion implantation in IIa type (111) diamond plates and similar annealings. 〈111〉 oriented nanopillars were produced on both types of nanolayers using focused ion beam (FIB) with Ga+ 30 keV maskless milling. The unusual optically detected magnetic resonances (ODMRs) were measured in a single nanopillars with a height of 500‒700 nm and of 250 nm in diameter covered by an amorphous a-C:Ga nanolayer in the 0‒20 G magnetic field. They demonstrated both a significant decrease in the gyromagnetic ratio and the quenching of photoluminescence (PL) signal from the NV– centers inclined to the nanopillar axis by the conductive a‑C:Ga nanolayer and stresses created by it. The multistep O2 RIE plasma etching restored the normal ODMR resonance frequencies and intensities for all four NV–center orientations in (111) diamond nanopillars.
Raman and ODMR Spectroscopy of NV Centers in Nanolayers and Nanopillars of ⟨111⟩ Diamond after Etching with a Focused Beam of Ga Ions
The spectral characteristics of the optically detected magnetic resonance of negatively charged nitrogen–vacancy (NV − ) centers in synthetic diamonds and nanopillars on their surface formed by a focused Ga + ion beam, when the lower spin sublevels are populated with microwave radiation, are studied. In the course of studies for emerging spin resonances at different values of the external magnetic field, both a significant decrease in the gyromagnetic ratio and a significant drop in the photoluminescence contrast are revealed for the directions of the NV − centers inclined to the axis of the nanopillars due to residual defects from ion etching recorded on Raman spectra in the form of peaks from amorphous carbon and graphite and the stresses they create.
Nitrogen-vacancy (NV) color centers in diamond are excellent quantum sensors possessing high sensitivity and nano-scale spatial resolution. Their integration in photonic structures is often desired, since it leads to an increased photon emission and also allows the realization of solid-state quantum technology architectures. Here, we report the fabrication of diamond nano-pillars with diameters up to 1000 nm by electron beam lithography and inductively coupled plasma reactive ion etching in nitrogen-rich diamonds (type Ib) with [100] and [111] crystal orientations. The NV centers were created by keV-He ion bombardment and subsequent annealing, and we estimate an average number of NVs per pillar to be 4300 ± 300 and 520 ± 120 for the [100] and [111] samples, respectively. Lifetime measurements of the NVs’ excited state showed two time constants with average values of τ1 ≈ 2 ns and τ2 ≈ 8 ns, which are shorter as compared to a single color center in a bulk crystal (τ ≈ 10 ns). This is probably due to a coupling between the NVs as well as due to interaction with bombardment-induced defects and substitutional nitrogen (P1 centers). Optically detected magnetic resonance measurements revealed a contrast of about 5% and average coherence and relaxation times of T2 [100] = 420 ± 40 ns, T2 [111] = 560 ± 50 ns, and T1 [100] = 162 ± 11 μs, T1 [111] = 174 ± 24 μs. These pillars could find an application for scanning probe magnetic field imaging.
Nitrogen-vacancy (NV) centers in diamonds have been an epicenter of research for diverse applications in quantum technologies. It is therefore imperative that their fabrication techniques are well understood and characterized for the technological scalability of these applications. A comparative study of the optical and spin properties of NVs created by ion implantation and chemical vapor deposition delta-doping is thus presented, combined with an investigation on the impact of annealing in vacuum at different temperatures. In addition, nanopillars are fabricated by electron beam lithography and reactive ion etching for enhanced photon collection efficiency. An extensive combination of characterization techniques is employed. Notably, the smallest nanopillars present fluorescence enhancements of factor around 50, compared to the unstructured regions. Annealing is also demonstrated to increase the optical contrast between the NVs' electronic states, the coherence and relaxation times both in bulk as in pillars. Regarding the NV preparation technique, the delta-doping is shown to create NVs with less lattice defects and strain compared to implantation. • Comparative study of optical and spin properties of implanted and δ-doped CVD NVs • Impact of structuring with nanopillars and annealing on the NV properties • Fluorescence enhancement factors of above 30 in 100–150 nm diameter pillars • 3-Fold increase in ODMR contrast of all samples after annealing • Increase of coherence and relaxation times after annealing
Precise control over the spatial distribution and charge state of nitrogen-vacancy (NV) centers in diamond is a key requirement for further advancing this platform in quantum sensing and photonic applications. Here, we investigate nitrogen ion implantation as a scalable method to engineer NV centers in bulk single-crystalline (SC) and a 5 μ m -thick polycrystalline (PC) diamond membrane. Nitrogen-doped regions (1–80 ppm) were fabricated using a 0.7 MeV ion beam and high-temperature annealing, with NV center formation verified by confocal fluorescence imaging and spectral analysis. In SC bulk diamond, we estimate the NV concentration from spectral analysis and model the fluorescence response as a function of implantation dose, capturing both the initial increase at low concentrations and a saturation behavior at higher doses due to quenching mechanisms. In contrast, PC diamond membranes show a weaker dependence at low implantation fluences, consistent with pre-existing nitrogen impurities, thus making a statistical model significantly more complex. The activation yield is found to be of order of 1%, which is lower than in N-rich diamond samples, as implanted N is predominantly interstitial. Photoluminescence spectroscopy indicates that NV 0 is the dominant charge state in both materials, with a laser-power-dependent redistribution between neutral and negative charge states. Optically detected magnetic resonance (ODMR) measurements in SC bulk diamond resolve the hyperfine structure and allow extraction of the dephasing time ( T 2 ∗ ), while in PC diamond membranes, where NV centers tend do form near the grain boundaries, the ODMR signals are observed but spectral resolution is currently limited by impurities, grain-dependent NV orientations, and photoluminescence background.
We investigate the possibilities to realize light extraction from single crystal diamond (SCD) nanopillars. This was achieved by dedicated 519 nm laser-induced spin-state initiation of negatively charged nitrogen vacancies (NV−). We focus on the naturally-generated by chemical vapor deposition (CVD) growth of NV−. Applied diamond was neither implanted with 14N+, nor was the CVD synthesized SCD annealed. To investigate the possibility of light extraction by the utilization of NV−’s bright photoluminescence at room temperature and ambient conditions with the waveguiding effect, we have performed a top-down nanofabrication of SCD by electron beam lithography (EBL) and dry inductively-coupled plasma/reactive ion etching (ICP-RIE) to generate light focusing nanopillars. In addition, we have fluorinated the diamond’s surface by dedicated 0 V SF6 ICP plasma. Light extraction and spin manipulations were performed with photoluminescence (PL) spectroscopy and optically detected magnetic resonance (ODMR) at room temperature. We have observed a remarkable effect based on the selective 0 V SF6 plasma etching and surprisingly, in contrast to literature findings, deactivation of NV− centers. We discuss the possible deactivation mechanism in detail.
The development of material-processing techniques that can be used to generate optical diamond nanostructures containing a single-color center is an important problem in quantum science and technology. In this work, we present the combination of ion implantation and top-down diamond nanofabrication in two scenarios: diamond nanopillars and diamond nanowires. The first device consists of a 'shallow' implant (∼20 nm) to generate nitrogen-vacancy (NV) color centers near the top surface of the diamond crystal prior to device fabrication. Individual NV centers are then mechanically isolated by etching a regular array of nanopillars in the diamond surface. Photon anti-bunching measurements indicate that a high yield (>10%) of the devices contain a single NV center. The second device demonstrates 'deep' (∼1 μm) implantation of individual NV centers into diamond nanowires as a post-processing step. The high single-photon flux of the nanowire geometry, combined with the low background fluorescence of the ultrapure diamond, allowed us to observe sustained photon anti-bunching even at high pump powers.