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.
We investigate the influence of plasma treatments, especially a 0V-bias, potentially low damage O
2 plasma as well as a biased Ar/SF
6/O
2 plasma on shallow, negative nitrogen vacancy (NV
−) centers. We ignite and sustain using our 0V-bias plasma using purely inductive coupling. To this end, we pre-treat surfaces of high purity chemical vapor deposited single-crystal diamond (SCD). Subsequently, we create $\sim
10nmdeepNV^-$ centers via implantation and annealing. Onto the annealed SCD surface, we fabricate nanopillar structures that efficiently waveguide the photoluminescence (PL) of shallow NV
−. Characterizing single NV
− inside these nanopillars, we find that the Ar/SF
6/O
2 plasma treatment quenches NV
− PL even considering that the annealing and cleaning steps following ion implantation remove any surface termination. In contrast, for our 0V-bias as well as biased O
2 plasma, we observe stable NV
− PL and low background fluorescence from the photonic nanostructures.
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.
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.
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
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.
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 properties of NVs for quantum information processing and magnetic sensing.