Dopant-assisted stabilization of negatively charged single nitrogen-vacancy centers in phosphorus-doped diamond at low temperatures
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-10-27 |
| Journal | npj Quantum Information |
| Authors | Jianpei Geng, Tetyana Shalomayeva, Mariia Gryzlova, Amlan Mukherjee, S. Santonocito |
| Institutions | University of Stuttgart, Kyoto University Institute for Chemical Research |
| Citations | 13 |
| Analysis | Full AI Review Included |
Dopant-Assisted NV Center Stabilization in P-Doped Diamond: Technical Analysis and 6CCVD Solutions
Section titled âDopant-Assisted NV Center Stabilization in P-Doped Diamond: Technical Analysis and 6CCVD SolutionsâThis document analyzes the research paper âDopant-assisted stabilization of negatively charged single nitrogen-vacancy centers in phosphorus-doped diamond at low temperaturesâ (Geng et al., 2023) to provide technical specifications and highlight how 6CCVDâs advanced MPCVD diamond capabilities can support and extend this critical quantum research.
Executive Summary
Section titled âExecutive SummaryâThis research successfully addresses a major bottleneck in solid-state quantum systems by achieving intrinsic stabilization of the negatively charged Nitrogen-Vacancy (NV-) center in diamond, eliminating the need for external repump lasers.
- Core Achievement: Stabilization of the NV- charge state in phosphorus-doped (P-doped) diamond at liquid helium temperatures (4 K).
- Mechanism: Photoionization of shallow phosphorus donors provides free electrons, significantly enhancing the NV° to NV- recombination pathway.
- Performance Gain: The elimination of the repump laser reduces system overhead and mitigates spurious effects like spectral diffusion, which typically degrade spin-photon interfaces.
- Key Finding: The recombination rate exhibits a linear dependence on laser power, clearly distinguishing this dopant-assisted mechanism from conventional quadratic laser-assisted processes.
- Material Requirement: High-quality, epitaxially grown P-doped diamond layers on (111)-oriented substrates are essential for achieving stable Photoluminescence-Excitation (PLE) spectra.
- Application Potential: This intrinsic stabilization is crucial for scaling quantum network applications and improving entanglement rates by removing time-consuming repump cycles.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results, focusing on material composition, operational conditions, and performance metrics.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Phosphorus Concentration | 5 x 1016 | atoms cm-3 | CVD-grown layer |
| Substrate Orientation | (111) | N/A | Ib-type diamond used for epitaxial growth |
| Operating Temperature | 4 | K | Liquid helium cryogenic setup |
| NV Resonant Excitation | 636 | nm | Used for NV centers created during growth |
| Implantation Species | 15N+ | N/A | Used for creating additional NV centers |
| Implantation Energy | 9.8 | keV | For 15N+ ions |
| Implantation Dose | 1.3 x 1010 | atoms cm-2 | For 15N+ ions |
| Spin Coherence Time (T2) | 1.94 | ms | NV centers created during growth |
| Spin Coherence Time (T2) | 11.53 | ”s | NV centers created by ion implantation |
| P Donor Energy Level | 0.57 | eV | Below the conduction band edge |
| Recombination Rate Dependence | Linear | N/A | Observed dependence on laser power (krec) |
Key Methodologies
Section titled âKey MethodologiesâThe stabilization and characterization of the NV centers relied on precise material engineering and advanced cryogenic optical techniques.
- Epitaxial Growth: Phosphorus-doped diamond layers were grown epitaxially via Chemical Vapor Deposition (CVD) onto Ib-type (111)-oriented diamond substrates, ensuring a specific P concentration (5 x 1016 atoms cm-3).
- NV Center Generation: NV centers were created using two methods: in situ during the growth process (resulting in longer T2) and ex situ via 15N+ ion implantation (9.8 keV).
- Photon Collection Enhancement: Arrays of nanopillars (400-500 nm apex size) were fabricated on the surface to maximize the photon collection efficiency, particularly for implanted defects.
- Cryogenic Confocal Setup: Measurements were conducted using a home-built cryogenic confocal microscope, maintaining the sample environment at 4 K (liquid helium).
- Resonant Excitation: A 636 nm resonant laser was used for continuous illumination and excitation, enabling the monitoring of the NV charge state via fluorescence.
- Charge Dynamics Analysis: Fluorescence time traces were recorded and fitted to extract the ionization (kion) and recombination (krec) rates, confirming the linear power dependence of krec attributed to P photo-ionization.
- Spectroscopy: Stable Photoluminescence-Excitation (PLE) spectra were obtained for the grown NV centers without the use of a conventional repump laser.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the high-purity, custom-engineered MPCVD diamond materials required to replicate, optimize, and scale this research for industrial quantum applications.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate the high-quality, doped diamond used in this study, researchers require materials with precise crystallographic orientation and controlled donor concentration.
| Research Requirement | 6CCVD Solution | Material Specification |
|---|---|---|
| P-Doping/N-Type | N-Type Doped Single Crystal Diamond (SCD) | Custom doping (e.g., Boron-Doped (BDD) capability confirms general doping expertise) to achieve target P concentrations (5 x 1016 atoms cm-3). |
| High Coherence | Optical Grade SCD | Ultra-low strain and defect density SCD, crucial for achieving the reported millisecond T2 coherence times for grown NV centers. |
| Substrate Orientation | Custom (111) SCD Substrates | While (100) is common, 6CCVD provides custom growth on (111) substrates, which is essential for optimizing NV alignment and spin properties in this specific research. |
| Thickness Control | SCD/PCD Wafers | Thickness control from 0.1 ”m up to 500 ”m (SCD/PCD layers) and substrates up to 10 mm, allowing for deep defect creation or thin film device integration. |
Customization Potential
Section titled âCustomization PotentialâThe optimization section of the paper discusses the need to control P concentration and potentially separate NV and P layers (delta-doping) to achieve narrower PLE linewidths. 6CCVDâs custom capabilities directly address these advanced requirements.
- Doping Optimization: 6CCVD offers precise control over dopant incorporation during MPCVD growth, enabling researchers to fine-tune the P concentration to optimize the balance between NV- stabilization and minimizing electric field noise (as discussed in the paperâs Discussion section).
- Custom Dimensions: We supply plates and wafers up to 125 mm (PCD) and large-area SCD, facilitating the transition from small research samples to scalable, inch-size quantum devices.
- Advanced Polishing: Achieving high-fidelity nanopillar arrays (as used for photon enhancement) requires an ultra-smooth starting surface. 6CCVD guarantees surface roughness of Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD.
- Metalization Services: Although not the focus of this paper, 6CCVD offers in-house metalization (Au, Pt, Pd, Ti, W, Cu) for integrating diamond quantum chips with microwave lines or electrical contacts necessary for advanced quantum protocols.
Engineering Support
Section titled âEngineering SupportâThe complexity of charge state dynamics and defect engineering requires specialized knowledge.
6CCVDâs in-house PhD team can assist with material selection and recipe development for similar NV Center Quantum Sensing and Computing projects. We provide consultation on optimizing growth parameters (temperature, pressure, gas flow) and material specifications (doping level, orientation) to ensure stable NV- population and narrow linewidths, accelerating the development of repump-free quantum devices.
Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Charge state instabilities have been a bottleneck for the implementation of solid-state spin systems and pose a major challenge to the development of spin-based quantum technologies. Here we investigate the stabilization of negatively charged nitrogen-vacancy (NV â ) centers in phosphorus-doped diamond at liquid helium temperatures. Photoionization of phosphorous donors in conjunction with charge diffusion at the nanoscale enhances NV 0 to NV â conversion and stabilizes the NV â charge state without the need for an additional repump laser. The phosphorus-assisted stabilization is explored and confirmed both with experiments and our theoretical model. Stable photoluminescence-excitation spectra are obtained for NV â centers created during the growth. The fluorescence is continuously recorded under resonant excitation to real-time monitor the charge state and the ionization and recombination rates are extracted from time traces. We find a linear laser power dependence of the recombination rate as opposed to the conventional quadratic dependence, which is attributed to the photo-ionization of phosphorus atoms.