Decoration of growth sector boundaries with nitrogen vacancy centers in as-grown single crystal high-pressure high-temperature synthetic diamond
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-09-30 |
| Journal | Physical Review Materials |
| Authors | P.L. Diggle, U.F.S. D’Haenens-Johansson, B.L. Green, C.M. Welbourn, Thu Nhi Tran Thi |
| Institutions | Gemological Institute of America, Engineering and Physical Sciences Research Council |
| Citations | 11 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Defect Engineering in Single Crystal Diamond
Section titled “Technical Documentation & Analysis: Defect Engineering in Single Crystal Diamond”This documentation analyzes the findings of the research paper concerning point defect incorporation in high-purity HPHT diamond, positioning 6CCVD’s advanced MPCVD capabilities as the optimal solution for researchers requiring ultra-high purity and precise defect engineering for quantum and optical applications.
Executive Summary
Section titled “Executive Summary”- Material Quality Validation: The analyzed HPHT diamond exhibits high crystalline quality with low dislocation density (< 10³ cm⁻²), confirming its suitability as a base material for advanced applications.
- Impurity Control Challenge: While the boron concentration in the critical {001} growth sector is exceptionally low (< 1 ppb), the overall nitrogen contamination remains a limiting factor for achieving true “quantum grade” performance, a purity level routinely achieved via MPCVD.
- Defect Identification: Three key point defects were identified: the negatively charged Nitrogen Vacancy (NV⁻), the Silicon Vacancy (SiV⁻), and a Nickel-related 1.40 eV center.
- Spatial Localization: NV⁻ centers were found to exclusively decorate the boundaries between {111} and {113} growth sectors, providing a mechanism to calculate relative growth rates.
- Orientation Control: The 1.40 eV nickel-related defect showed strong preferential orientation aligned with the <111> growth direction, while the NV⁻ defect showed no orientation due to thermal re-orientation at HPHT growth temperatures.
- CVD Advantage: The paper implicitly validates the superior chemical purity control of CVD, noting that HPHT material must reduce nitrogen contamination to < 1 ppb to potentially outperform quantum-grade CVD diamond. 6CCVD specializes in delivering this ultra-high purity material.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the analysis of the HPHT diamond sample:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Sample Dimensions | 4.0 x 4.0 x 0.5 | mm | HPHT plate cut for analysis |
| Dislocation Density (Average) | < 10³ | cm⁻² | Low internal strain material quality |
| Substitutional Nitrogen [N⁰] (Average) | 6.5 ± 1 | ppb | Measured via EPR (bulk average) |
| Boron [B] Concentration ({001} Sector) | < 1 | ppb | Lowest impurity sector |
| Boron [B] Concentration ({111} Sector) | 84 ± 10 | ppb | Highest impurity sector |
| Luminescent Defect Concentration (Detection Limit) | 10¹¹ (or 10⁻³ ppb) | cm⁻³ | Confocal PL detection limit |
| NV⁻ Single Center Resolution Limit | 1.76 x 10¹¹ | cm⁻³ | Bulk defect concentration limit via g² |
| HPHT Growth Temperature Range | 1350 - 1600 | °C | Typical synthesis conditions |
| SiV⁻ Zero Phonon Line (ZPL) | 737 | nm | Observed in bulk {111} sectors |
| Nickel Defect (1.40 eV) ZPL | 884 | nm | Observed in bulk {111} sectors |
| NV⁻ Activation Energy (Ea) | ≈ 4.0 | eV | Used for re-orientation modeling |
Key Methodologies
Section titled “Key Methodologies”The study employed a comprehensive suite of characterization techniques to analyze the structural quality and defect incorporation mechanisms of the as-grown HPHT diamond:
- Sample Preparation: A 4.0 x 4.0 x 0.5 mm plate was cut from an HPHT diamond synthesized in a Co-Fe-C system using a proprietary nitrogen getter. The large face was oriented within 1° of the (001) plane.
- Structural Analysis: White light cross polarization imaging and white beam X-ray topography (XRT) were used to assess internal strain, extended defects, and dislocation density.
- Bulk Impurity Measurement: Electron Paramagnetic Resonance (EPR) was utilized to determine the mean neutral substitutional nitrogen concentration [N⁰] across the entire sample.
- Sector-Specific Impurity Measurement: Low temperature (77 K) Cathodoluminescence (CL) imaging and spectroscopy were employed to map growth sectors and quantify substitutional boron concentration [B] based on the Boron Bound Exciton (BE) signal.
- Point Defect Mapping: Room temperature Confocal Photoluminescence (PL) microscopy (using 488 nm and 532 nm excitation) was used to spatially map the distribution of NV⁻, SiV⁻, and the 1.40 eV nickel-related defects.
- Single Defect Quantification: Second order photon autocorrelation (g²) measurements were performed to classify the NV⁻ centers as single emitters or ensembles, establishing a bulk defect concentration limit of 1.76 x 10¹¹ cm⁻³.
- Defect Orientation Analysis: Optically Detected Magnetic Resonance (ODMR) and rotation of linear excitation polarization were used to investigate the preferential alignment of the defect symmetry axes relative to the growth direction.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”The research demonstrates the critical need for ultra-high purity, low-strain diamond substrates for quantum applications, a domain where 6CCVD’s MPCVD technology excels over HPHT synthesis. 6CCVD provides the necessary materials and customization to replicate and advance this research, particularly in achieving the sub-ppb impurity levels required for long spin coherence times.
| Research Requirement/Challenge | 6CCVD MPCVD Solution | Technical Advantage |
|---|---|---|
| Challenge: Achieving N < 1 ppb in bulk material (HPHT limitation). | Quantum Grade Single Crystal Diamond (SCD) | MPCVD allows precise control of gas chemistry, routinely achieving N and B concentrations < 1 ppb, minimizing paramagnetic impurities that cause spin decoherence. |
| Requirement: High-quality substrates for post-growth defect creation (e.g., ion implantation or laser writing). | Ultra-Low Strain SCD Substrates (0.1 µm - 500 µm thickness) | Our SCD material is optimized for subsequent processing, providing the low dislocation density and high purity necessary for stable, high-fidelity quantum emitters. |
| Requirement: Large area for scaling devices (HPHT sample was 4x4 mm). | Custom Dimensions up to 125 mm (PCD) / Large Area SCD | We supply SCD and PCD plates/wafers in custom dimensions far exceeding typical HPHT limits, enabling industrial scaling of optical and quantum devices. |
| Requirement: High-resolution optical access (NA = 1.4 objective used). | SCD Polishing (Ra < 1 nm) | Our proprietary polishing achieves atomic-scale smoothness (Ra < 1 nm for SCD), minimizing surface scattering and optimizing coupling efficiency for high-NA confocal microscopy and integrated photonics. |
| Requirement: Integration of electrical contacts (Au sputtering used for CL). | In-House Custom Metalization | 6CCVD offers internal deposition of thin films (Au, Pt, Pd, Ti, W, Cu) for creating co-planar waveguides (used in ODMR) or electrical contacts directly onto the diamond surface, accelerating device prototyping. |
| Requirement: Controlled incorporation of SiV⁻ or other color centers. | Doped SCD/PCD Wafers | We offer controlled doping during the CVD growth process to engineer specific defect concentrations (e.g., Si, N, B) and spatial distributions, crucial for integrated quantum circuits and sensing arrays. |
Applicable Materials
Section titled “Applicable Materials”- Optical Grade SCD: Ideal for replicating the confocal PL and CL experiments, offering superior transparency and low birefringence.
- Quantum Grade SCD: Specifically required to overcome the nitrogen contamination limits of the HPHT material, ensuring N and B impurities are below 1 ppb for optimal NV⁻ or SiV⁻ spin coherence.
- Polycrystalline Diamond (PCD): Available in large formats (up to 125 mm) and various thicknesses (0.1 µm - 500 µm) for high-power optical windows or thermal management applications where ultra-high purity is less critical than size.
Engineering Support
Section titled “Engineering Support”6CCVD’s in-house PhD team specializes in defect engineering and material optimization. We can assist researchers with material selection, orientation control (e.g., <111> growth for preferential defect alignment), and post-growth processing strategies for similar quantum sensing and solid-state physics projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Large (> 100 mm$^3$), relatively pure (type II) and low birefringence single\ncrystal diamond can be produced by high pressure high temperature (HPHT)\nsynthesis. In this study we examine a HPHT sample of good crystalline\nperfection, containing less than 1 ppb (part per billion carbon atoms) of boron\nimpurity atoms in the {001} growth sector and only tens of ppb of nitrogen\nimpurity atoms. It is shown that the boundaries between {111} and {113} growth\nsectors are decorated by negatively charged nitrogen vacancy centres (NV$^-$):\nno decoration is observed at any other type of growth sector interface. This\ndecoration can be used to calculated the relative {111} and {113} growth rates.\nThe bulk (001) sector contains concentrations of luminescent point defects\n(excited with 488 and 532 nm wavelengths) below 10$^{11}$ cm$^{-3}$ (10$^{-3}$\nppb). We observe the negatively charged silicon-vacancy (SiV$^-$) defect in the\nbulk {111} sectors along with a zero phonon line emission associated with a\nnickel defect at 884 nm (1.40 eV). No preferential orientation is seen for\neither NV$^-$ or SiV$^-$ defects, but the nickel related defect is oriented\nwith its trigonal axis along the <111> sector growth direction. Since the\nNV$^-$ defect is expected to readily re-orientate at HPHT diamond growth\ntemperatures, no preferential orientation is expected for this defect but the\nlack of preferential orientation of SiV$^-$ in {111} sectors is not explained.\n
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
Section titled “References”- 2015 - Handbook of Crystal Growth
- 2015 - Components Packaging Laser System