Sulfur in diamond and its effect on the creation of nitrogen-vacancy defect from ab initio simulations
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-03-17 |
| Journal | Physical Review Research |
| Authors | Nima Ghafari Cherati, Anton Pershin, ĂdĂĄm Gali |
| Institutions | HUN-REN Wigner Research Centre for Physics, GfK (United States) |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Sulfur-Mediated NV Center Engineering
Section titled âTechnical Documentation & Analysis: Sulfur-Mediated NV Center Engineeringâ6CCVD specializes in providing high-purity, custom MPCVD diamond materials (SCD/PCD) essential for advanced quantum and electronic applications.
Executive Summary
Section titled âExecutive SummaryâThis research utilizes hybrid Density Functional Theory (HSE06) to elucidate the mechanism by which sulfur doping dramatically enhances the creation efficiency of negatively charged Nitrogen-Vacancy (NV) centers in Chemical Vapor Deposited (CVD) diamond, a critical material platform for quantum technologies.
- Enhanced NV Creation: The study confirms the microscopic mechanism behind the experimentally observed 75% NV center creation efficiency achieved in sulfur-doped diamond layers via nitrogen ion implantation.
- Double Donor Mechanism: Substitutional Sulfur (S${s}$) acts as an efficient double donor (S${s}^{2+}$), providing two electrons to the lattice.
- Vacancy Stabilization: The S${s}^{2+}$ charge state effectively stabilizes mobile vacancies (V) in a negative charge state (V$^{-}$ or V$^{2-}$), preventing their aggregation into detrimental Divacancies (V${2}$).
- NV Promotion: By preventing V${2}$ formation, the negatively charged vacancies are instead channeled to combine with substitutional nitrogen (N${s}$), promoting the formation of the desired NV centers.
- Stable Defect Environment: The Sulfur-Vacancy (SV) complex is identified as the most stable sulfur-related defect, which is optically inactive and provides a photostable, electron spin-free environment, potentially improving NV coherence times.
- Engineering Insight: The results provide crucial data on formation energies and charge transition levels, guiding the precise engineering of annealing temperatures (e.g., above 800 °C for V(-) mobility) required to maximize NV yield.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the ab initio simulations and referenced experimental context, critical for material and process engineering.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| NV Creation Efficiency (S-doped) | 75.3 | % | Highest reported experimental yield (Ref. [8]) |
| Diamond Band Gap (E${c}$ - E${v}$) | 5.4 | eV | Calculated HSE06 value |
| Substitutional Sulfur Donor Level (S$_{s}$) | E$_{c}$ - 1.6 | eV | (+1 |
| Substitutional Sulfur Double Donor Level (S$_{s}$) | E$_{c}$ - 2.9 | eV | (2+ |
| Neutral Vacancy Diffusion Activation Energy (V(0)) | 2.3 ± 0.3 | eV | Experimental activation energy |
| V(0) Mobility Threshold | ~600 | °C | Estimated temperature for V(0) mobility |
| V(-) Mobility Threshold | ~800 | °C | Estimated temperature for V(-) mobility |
| SV Complex Formation Binding Energy | 8.7 | eV | Binding energy for V(0) + S$_{s}$(2+) $\rightarrow$ SV(0) |
| Divacancy Formation Binding Energy | 4.2 | eV | Binding energy for V(0) + V(0) $\rightarrow$ V$_{2}$(0) |
| Experimental Annealing Temperature | 1200 | °C | Used in related S implantation studies (Ref. [45]) |
Key Methodologies
Section titled âKey MethodologiesâThe theoretical investigation relied on highly accurate computational methods to model defect behavior in diamond, providing a roadmap for experimental replication and optimization.
- Computational Framework: Calculations were performed using ab initio Density Functional Theory (DFT) implemented in VASP.
- Functional Selection: The screened hybrid density functional HSE06 was employed, specifically chosen for its ability to accurately reproduce the experimental band gap of diamond (5.4 eV) and defect levels within the gap (typical accuracy of 0.1 eV).
- Supercell Geometry: Defects were modeled within a large 4 x 4 x 4 cubic 512-atom supercell, ensuring minimal interaction between periodic images.
- Convergence Criteria: Structural relaxation was performed to strict convergence thresholds: 10-5 eV for total energy and 10-3 eV/Ă for ionic forces.
- Chemical Potential Referencing: Chemical potentials for Sulfur (S) were referenced to the total energy of an S$_{8}$ crystal, and Hydrogen (H) was referenced to a slab model of a hydrogen-terminated diamond surface.
- Defect Species Analyzed: A comprehensive set of sulfur-related defects were studied, including Interstitial Sulfur (S${i}$), Substitutional Sulfur (S${s}$), Sulfur-Vacancy (SV), Sulfur-Vacancy-Vacancy (SVV), and their complexes with Interstitial Hydrogen (SH, SVH, SVVH).
- Property Calculation: Formation energies, charge transition levels (referenced to E${c}$ for donors and E${v}$ for acceptors), and hyperfine tensors were calculated to predict magnetic and electronic properties.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful replication and extension of this researchâachieving high-yield, high-coherence NV centersârequires ultra-high-purity MPCVD diamond substrates with precise doping and surface engineering. 6CCVD is uniquely positioned to supply the necessary materials and technical support.
Applicable Materials for Quantum Defect Engineering
Section titled âApplicable Materials for Quantum Defect Engineeringâ| Application Requirement | 6CCVD Material Recommendation | Rationale |
|---|---|---|
| Starting Substrate | Electronic Grade SCD (Single Crystal Diamond) | Ultra-low intrinsic defect density (N < 1 ppb) is essential to ensure that implanted S and N are the dominant defects, maximizing NV yield and coherence. |
| Scalable Platform | Optical Grade PCD (Polycrystalline Diamond) | Available in large formats (up to 125mm wafers) for high-throughput ion implantation and scalable quantum device fabrication. |
| Dopant Source | Custom Sulfur-Doped CVD Layers | We offer custom MPCVD growth recipes to incorporate Sulfur (S) during deposition, providing the critical S$_{s}^{2+}$ double donor required for vacancy stabilization. |
| High-Coherence Environment | High-Purity SCD/PCD with Ra < 1nm Polishing | The SV defect provides a spin-free environment. Maintaining high material purity and surface quality is paramount for achieving long spin coherence times (T$_{2}$). |
Customization Potential for Advanced Research
Section titled âCustomization Potential for Advanced ResearchâThe research highlights the need for precise control over material composition and post-processing steps (implantation and annealing). 6CCVD offers comprehensive customization services to meet these demands:
- Custom Dimensions and Thickness: While the paper references implantation depths of âtens of nanometers,â 6CCVD provides SCD and PCD layers with thickness control from 0.1”m up to 500”m, allowing researchers to define the exact active layer depth for optimal defect placement.
- Large-Area Substrates: We supply PCD wafers up to 125mm in diameter, enabling the transition from small-scale research to scalable quantum device manufacturing.
- Advanced Metalization Services: For integrating NV centers into microwave or optical circuits, 6CCVD offers in-house metalization using materials such as Au, Pt, Pd, Ti, W, and Cu, applied with high precision.
- Surface Engineering: We guarantee ultra-low surface roughness (Ra < 1nm for SCD), which is critical for minimizing implantation damage and ensuring high-fidelity optical readout.
Engineering Support
Section titled âEngineering SupportâThe paper emphasizes that maximizing NV creation yield requires careful engineering of annealing parameters to control the competition between SV complex formation and S$_{s}$ stability.
- Defect Control Consultation: 6CCVDâs in-house PhD team specializes in defect physics and MPCVD growth kinetics. We provide expert consultation on material selection and post-growth processing parameters (e.g., annealing temperatures and ramp rates) for similar NV Center Creation and Quantum Sensing projects.
- Global Supply Chain: We ensure reliable global delivery (DDU default, DDP available) of highly specialized diamond materials, supporting international research collaborations.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The negatively charged nitrogen-vacancy (NV) center is one of the most significant and widely studied defects in diamond that plays a prominent role in quantum technologies. The precise engineering of the location and concentration of NV centers is of great importance in quantum technology applications. To this end, irradiation techniques such as nitrogen-molecule ion implantation are applied. Recent studies have reported enhanced NV center creation and activation efficiencies introduced by nitrogen molecule ion implantation in doped diamond layers, where the maximum creation efficiency at <a:math xmlns:a=âhttp://www.w3.org/1998/Math/MathMLâ><a:mrow><a:mo>âŒ</a:mo><a:mn>75</a:mn><a:mo>%</a:mo></a:mrow></a:math> has been achieved in sulfur-doped layers. However, the microscopic mechanisms behind these observations and the limits of the efficiencies are far from understood. In this study, we employ hybrid density-functional-theory calculations to compute the formation energies, charge transition levels, and the magneto-optical properties of various sulfur defects in diamond where we also consider the interaction of sulfur and hydrogen in chemical vapor-deposited diamond layers. Our results imply that the competition between the donor substitutional sulfur and the hyperdeep acceptor sulfur-vacancy complex is an important limiting factor on the creation efficiency of the NV center in diamond. However, both species are able to trap interstitial hydrogen from diamond, which favorably mediates the creation of NV centers in chemical vapor-deposited diamond layers.