Tailoring spin defects in diamond by lattice charging
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-05-17 |
| Journal | Nature Communications |
| Authors | Felipe FĂĄvaro de Oliveira, Denis Antonov, Ya Wang, Philipp Neumann, Seyed Ali Momenzadeh |
| Institutions | University of Stuttgart, UniversitÀt Ulm |
| Citations | 117 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Tailoring Spin Defects in Diamond by Lattice Charging
Section titled âTechnical Documentation & Analysis: Tailoring Spin Defects in Diamond by Lattice ChargingâSource Paper: de Oliveira, F. F. et al. Tailoring spin defects in diamond by lattice charging. Nat. Commun. 8, 15409 (2017).
Executive Summary
Section titled âExecutive SummaryâThis research demonstrates a breakthrough method for engineering high-performance nitrogen-vacancy (NV) centers in diamond, critical for advancing solid-state quantum systems.
- Core Achievement: Achieved a tenfold improvement in spin coherence times ($T_2$) and a twofold improvement in NV center formation yield for shallow defects ($2-8$ nm depth).
- Mechanism: The technique utilizes a planar $p^{+}-i$ junction structure (Boron-Doped layer on Ultra-Pure SCD substrate) to generate a space-charge layer of free carriers (holes).
- Defect Suppression: Charging of implantation-induced vacancies ($V^{2+}$) within this layer suppresses the formation of detrimental di-vacancy ($V_2$) complexes during $950$ °C thermal annealing.
- Performance Metrics: Single NV centers exhibited long spin-lattice relaxation times ($T_1 > 5$ ms) and coherence times ($T_2$) up to $\sim 180$ ”s, confirming the pristine quality of the processed diamond lattice.
- Material Requirement: Success relies critically on the precise MPCVD growth of ultra-pure intrinsic diamond and heavily Boron-Doped Diamond (BDD) layers with nanometre thickness control.
- Application Impact: These results significantly improve the engineering of quantum devices, including nanoscale magnetometry and quantum computation, by mitigating implantation-induced lattice damage.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the research paper, highlighting the performance gains achieved using the lattice charging technique.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| $T_2$ Coherence Time Enhancement | Tenfold | Factor | Improvement over reference area for shallow NV centers (< 5 nm) |
| Maximum $T_2$ Coherence Time | $\sim 180$ | ”s | Observed for NV centers confined within 2-8 nm depth |
| $T_1$ Spin Relaxation Time | $>5$ | ms | Achieved for single NV centers |
| NV Center Formation Yield Enhancement | Twofold | Factor | Observed across 2.5, 5.0, and 9.8 keV implantation energies |
| Boron Acceptor Concentration ($p^{+}$ layer) | $\sim 10^{20}$ | cm-3 | Required concentration for the heavily doped layer |
| Nitrogen Implantation Energies | 2.5, 5.0, 9.8 | keV | Used $^{15}N^{+}$ ions for shallow implantation |
| Thermal Annealing Temperature | 950 | °C | Performed under high vacuum ($<10^{-6}$ mbar) |
| Boron-Doped Layer Thickness ($d_{p+}$) | 6, 12 | nm | MPCVD grown sacrificial layer |
| Substrate Impurity Concentration ($i$ layer) | $\sim 10^{14}$ | cm-3 | Concentration of residual donors (e.g., Nitrogen) |
| Final Surface Roughness (SCD) | Ra < 1 | nm | Required for as-polished SCD substrates |
Key Methodologies
Section titled âKey MethodologiesâThe successful fabrication of high-coherence shallow NV centers relied on precise MPCVD growth and controlled post-processing steps.
- Substrate Selection: Use of ultra-pure, [100]-oriented Single Crystal Diamond (SCD) substrates with extremely low nitrogen and boron concentrations ($<1$ p.p.b. impurities).
- $p^{+}$-Layer Overgrowth: Heavily Boron-Doped Diamond (BDD) layers (6 nm or 12 nm thickness, $N_A \sim 10^{20}$ cm-3) were epitaxially grown via Microwave Plasma Chemical Vapor Deposition (MPCVD) using a solid boron rod source for sharp doping profiles.
- Ion Implantation: Low-energy implantation of $^{15}N^{+}$ ions (2.5, 5.0, or 9.8 keV) using a focused ion beam at a $3^{\circ}$-off angle to localize defects within the space-charge layer.
- Thermal Annealing: Samples were annealed at $950$ °C under high vacuum for approximately 2 hours to mobilize vacancies, allowing them to combine with nitrogen atoms to form NV centers, while the lattice charging suppressed $V_2$ complex formation.
- Sacrificial Layer Removal: A final plasma etching step (7 nm removal) using oxygen inductively coupled plasma was performed to remove the sacrificial BDD layer, resulting in a pristine, oxygen-terminated surface essential for shallow NV performance.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials and precision engineering services required to replicate, scale, and extend the quantum research presented in this paper.
Applicable Materials
Section titled âApplicable MaterialsâThe success of the $p^{+}-i$ junction structure hinges on the quality and precise doping of the CVD layers. 6CCVD provides the necessary materials:
| Material Requirement | 6CCVD Solution | Technical Specification Match |
|---|---|---|
| Intrinsic Layer ($i$) | Ultra-Low Nitrogen SCD Substrates | SCD material with residual nitrogen concentration below $10^{14}$ cm-3, ensuring minimal background noise. |
| Doping Layer ($p^{+}$) | Heavy Boron Doped Diamond (BDD) | Custom BDD layers capable of achieving $N_A$ up to $10^{20}$ cm-3, essential for creating the required space-charge layer dynamics. |
| Substrate Format | SCD Substrates (up to 10mm thick) | High-quality, electronic-grade SCD required for the base material. |
Customization Potential
Section titled âCustomization PotentialâThe research utilized nanometre-scale layers (6 nm, 12 nm) and required precise surface preparation. 6CCVDâs custom capabilities directly address these needs:
- Precision Thickness Control: 6CCVD specializes in growing SCD and BDD layers with thickness control from $0.1$ ”m up to $500$ ”m. We can reliably produce the nanometre-thin BDD layers required for optimal $p^{+}-i$ junction performance.
- Advanced Polishing: Our internal polishing capabilities achieve surface roughness Ra < 1 nm for SCD, providing the pristine, low-damage surface necessary for low-energy ion implantation and subsequent shallow NV center performance.
- Custom Dimensions: While the paper used small samples, 6CCVD can supply custom plates and wafers up to 125 mm (PCD), enabling scaling for industrial quantum device fabrication.
Engineering Support
Section titled âEngineering SupportâThe complexity of tailoring defect formation kinetics requires deep material science expertise.
- MPCVD Recipe Optimization: 6CCVDâs in-house PhD team specializes in optimizing MPCVD growth parameters to control dopant concentration and layer thickness with high precision, crucial for engineering the exact space-charge layer dynamics required for Quantum Device Engineering and Nanoscale Sensing.
- Post-Processing Integration: We offer consultation on post-growth processing, including surface termination (e.g., oxygen termination via plasma etching, as used in the paper) to ensure optimal spin properties for near-surface NV centers.
- Metalization Services: For researchers integrating these NV centers into functional quantum circuits, 6CCVD offers custom metalization services (including Au, Pt, Ti, W, Cu) for creating electrical contacts or reference layers (e.g., for $T_1$ calibration using $Gd^{3+}$ ions).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.