Identification and Reversible Optical Switching of NV+ Centers in Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-03-30 |
| Journal | Advanced Functional Materials |
| Authors | Marcel Dickmann, Lucian Mathes, Ricardo Helm, Vassily Vadimovitch Burwitz, Werner Egger |
| Institutions | Technical University of Munich, Heinz Maier-Leibnitz Zentrum |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Analysis & Documentation: Reversible Optical Switching of NV+ Centers in Diamond
Section titled âTechnical Analysis & Documentation: Reversible Optical Switching of NV+ Centers in DiamondâExecutive Summary
Section titled âExecutive SummaryâThis research successfully identifies and characterizes the positively charged Nitrogen-Vacancy (NV+) center in high-purity CVD diamond, a critical step for advanced quantum technologies.
- NV+ Identification: Experimental confirmation of the elusive NV+ center, previously only inferred, using Positron Annihilation Lifetime Spectroscopy (PALS) combined with in situ light illumination.
- Reversible Switching: Demonstration of reversible optical charge state switching from NV+ to the detectable neutral state (NV0).
- Critical Energy Threshold: The charge transition (NV+ to NV0) requires a threshold photon energy of 1.234(8) eV, aligning with theoretical predictions.
- Metastable State Lifetime: The resulting NV0 state is metastable in complete darkness, decaying back to NV+ with a characteristic lifetime of 1.73(22) hours.
- Material Requirement: The study relies on ultra-low impurity, single crystal CVD diamond to ensure controlled defect creation via N+ implantation and subsequent high-temperature annealing (1200 °C).
- Quantum Relevance: These findings are essential for developing long-lived quantum data storage and scalable quantum computer architectures utilizing the NV+ centerâs unique spin properties.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental methodology and results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Initial Nitrogen Purity | < 5 | ppb | Single Crystal CVD Diamond (SCD) |
| Initial Boron Purity | < 1 | ppb | Single Crystal CVD Diamond (SCD) |
| Crystal Orientation | (100) | N/A | Substrate used for implantation |
| N+ Implantation Energy | 0.5 | MeV | Used to create NV precursors |
| N+ Implantation Fluence | 1.0 · 1014 | cm-2 | Chosen for high NV concentration |
| Annealing Temperature | 1200 | °C | Used for NV center formation |
| Annealing Time | 2 | h | Used for NV center formation |
| NV+ to NV0 Transition Energy | 1.234(8) | eV | Threshold photon energy (Eph) |
| NV0 Decay Time (in darkness) | 1.73(22) | h | Characteristic lifetime (t1/e) |
| Calculated Bulk Positron Lifetime | 103 | ps | Perfect diamond lattice |
| Measured NV Center Lifetime | 145(12) | ps | Associated with NV0 or NV- centers |
| Positron Implantation Depth (12 keV) | 596 | nm | Overlaps well with N+ distribution |
Key Methodologies
Section titled âKey MethodologiesâThe experimental success hinges on precise material preparation and advanced spectroscopic techniques:
- High-Purity Substrate Preparation: Utilization of commercial single crystal CVD diamond with ultra-low native nitrogen (< 5 ppb) and boron (< 1 ppb) to ensure defect control.
- Controlled Defect Introduction: Implantation of 0.5 MeV N+ ions at a fluence of 1.0 · 1014 cm-2 to introduce nitrogen and vacancies without causing bulk amorphization.
- Thermal Activation: Subsequent high-temperature annealing at 1200 °C for 2 hours to mobilize vacancies, allowing them to bind with substitutional nitrogen to form NV centers.
- Depth-Resolved Positron Spectroscopy: Application of Mono-energetic Positron Spectroscopy (MePS) at variable energies (4 keV and 12 keV) to probe defect structures at specific depths (82 nm and 596 nm).
- In Situ Charge Manipulation: Combination of Doppler-Broadening Spectroscopy (DBS) and PALS with monochromatic light illumination (1.1 - 1.4 eV range) to induce and monitor the NV+ to NV0 charge transition.
- DFT Verification: Density Functional Theory (DFT) calculations were used to predict positron lifetimes for various defects (NV0, NV-, V1, Vn clusters) to verify experimental PALS results.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the foundational materials and customization services required to replicate, extend, and scale this critical quantum research.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the controlled NV center formation and high-fidelity measurements demonstrated in this paper, researchers require the highest quality starting material:
- Optical Grade Single Crystal Diamond (SCD): The core material used in this study. 6CCVD supplies ultra-high purity SCD with native nitrogen levels typically < 1 ppb. This low background impurity is essential for controlling the Fermi level and ensuring that implanted nitrogen dominates the NV center population.
- Boron-Doped Diamond (BDD): The paper notes that NV+ formation requires a Fermi level close to the valence band, often achieved by acceptor doping (e.g., boron). 6CCVD offers custom BDD materials, allowing precise control over boron concentration to tune the Fermi level and optimize the initial NV+ population for quantum device integration.
Customization Potential
Section titled âCustomization Potentialâ6CCVDâs advanced MPCVD and post-processing capabilities directly address the needs of quantum material engineering:
| Research Requirement | 6CCVD Capability | Technical Specification |
|---|---|---|
| Substrate Dimensions | Custom Plates and Wafers | SCD up to 500 ”m thick; PCD up to 125mm diameter |
| Surface Quality | Ultra-Precision Polishing | SCD: Ra < 1 nm; Inch-size PCD: Ra < 5 nm |
| Orientation | Specific Crystal Cuts | Available (100) orientation, matching the studyâs requirements |
| Post-Processing | Metalization Services | In-house deposition of Au, Pt, Pd, Ti, W, Cu for electrical contacts (critical for bias-voltage switching applications) |
| Thickness Control | SCD Layer Growth | SCD layers available from 0.1 ”m up to 500 ”m, allowing precise control over the active quantum layer depth |
Engineering Support
Section titled âEngineering SupportâThe successful manipulation of NV charge states requires deep expertise in defect engineering and material science.
- Defect Engineering Consultation: 6CCVDâs in-house PhD team can assist researchers in optimizing material selection and specifications for similar NV Center Quantum Technology projects, including advising on optimal starting purity, target implantation fluence, and post-growth annealing protocols (like the 1200 °C anneal used here).
- Global Logistics: We ensure reliable, secure global shipping (DDU default, DDP available) of sensitive, high-value diamond substrates directly to research facilities worldwide.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Positive nitrogenâvacancy centers (NV + ) in diamond are predicted to exist in conjunction with neutral (NV 0 ) and negative (NV â ) centers. However, the existence of NV + has only been indirectly inferred through a shift of the Fermi level. Evidence of NV + coexisting with NV 0 and NV - in diamond has not yet been observed. In this paper, positron annihilation spectroscopy in combination with in situ light illumination is applied, in order to investigate the presence of NV + centers in nitrogen implanted and subsequently annealed diamond. Switching of NV + to NV 0 centers is observed with a threshold photon energy of 1.234(8) eV. In complete darkness, a decay of NV 0 centers with a decay time of 1.73(22) h can be detected. In conclusion, previously converted NV 0 centers are metastable and partially decay in darkness, leading to the reformation of NV + centers.