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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”
MetadataDetails
Publication Date2020-09-30
JournalPhysical Review Materials
AuthorsP.L. Diggle, U.F.S. D’Haenens-Johansson, B.L. Green, C.M. Welbourn, Thu Nhi Tran Thi
InstitutionsEuropean Synchrotron Radiation Facility, Engineering and Physical Sciences Research Council
Citations11
AnalysisFull 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 (< 10Âł cm⁻ÂČ), 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:

ParameterValueUnitContext
Sample Dimensions4.0 x 4.0 x 0.5mmHPHT plate cut for analysis
Dislocation Density (Average)< 10Âłcm⁻ÂČLow internal strain material quality
Substitutional Nitrogen [N⁰] (Average)6.5 ± 1ppbMeasured via EPR (bulk average)
Boron [B] Concentration ({001} Sector)< 1ppbLowest impurity sector
Boron [B] Concentration ({111} Sector)84 ± 10ppbHighest impurity sector
Luminescent Defect Concentration (Detection Limit)10ÂčÂč (or 10⁻³ ppb)cm⁻³Confocal PL detection limit
NV⁻ Single Center Resolution Limit1.76 x 10ÂčÂčcm⁻³Bulk defect concentration limit via gÂČ
HPHT Growth Temperature Range1350 - 1600°CTypical synthesis conditions
SiV⁻ Zero Phonon Line (ZPL)737nmObserved in bulk {111} sectors
Nickel Defect (1.40 eV) ZPL884nmObserved in bulk {111} sectors
NV⁻ Activation Energy (Ea)≈ 4.0eVUsed 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:

  1. 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.
  2. 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.
  3. Bulk Impurity Measurement: Electron Paramagnetic Resonance (EPR) was utilized to determine the mean neutral substitutional nitrogen concentration [N⁰] across the entire sample.
  4. 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.
  5. 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.
  6. Single Defect Quantification: Second order photon autocorrelation (gÂČ) measurements were performed to classify the NV⁻ centers as single emitters or ensembles, establishing a bulk defect concentration limit of 1.76 x 10ÂčÂč cm⁻³.
  7. 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/Challenge6CCVD MPCVD SolutionTechnical 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 ”m - 500 ”m 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 SCDWe 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 Metalization6CCVD 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 WafersWe 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 ”m - 500 ”m) 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”
  1. 2015 - Handbook of Crystal Growth
  2. 2015 - Components Packaging Laser System

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