NV-like defects more common than four-leaf clovers - A perspective on high-throughput point defect data

At a Glance

Metadata	Details
Publication Date	2025-10-13
Journal	Applied Physics Letters
Authors	Joel Davidsson
Institutions	Linköping University
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Throughput Point Defect Data

Executive Summary

This analysis leverages the high-throughput computational screening results presented in “NV-like Defects More Common Than Four-Leaf Clovers” to validate and accelerate the development of solid-state spin qubits, emphasizing the critical role of high-quality MPCVD diamond substrates.

Defect Abundance Confirmed: High-throughput screening (ADAQ) identified 287 NV-like defect entries across 33 materials, confirming that suitable quantum defects are significantly more common than previously assumed (conservative estimate: 1 in 500).
Diamond as Premier Host: The research validates diamond (SCD) as a premier host, confirming stability and optical properties for the Nitrogen-Vacancy (NV) center and Group IV (XV) defects (SiV, GeV, SnV, PbV).
Key Defect Criteria: NV-like defects are characterized by thermodynamic stability (ε < 30 meV), high spin (S ≥ 1), and strong optical features (Zero Phonon Line (ZPL) > 0.5 eV, Transition Dipole Moment (TDM) > 3 Debye).
Computational Accuracy: The PBE functional used in the screening workflow consistently underestimates ZPLs in diamond by approximately 0.25 eV compared to experimental values, necessitating precise material characterization and defect engineering in the experimental phase.
6CCVD Value Proposition: Successful realization of these predicted defects requires ultra-pure, low-strain Single Crystal Diamond (SCD) substrates, precise doping/implantation, and advanced surface preparation (Ra < 1 nm), all of which are core 6CCVD capabilities.

Technical Specifications

The following table extracts key quantitative data points for known and predicted NV-like defects in diamond, the primary host material relevant to 6CCVD’s core product line.

Parameter	Value	Unit	Context
Host Materials Screened	33	N/A	Diamond, 4H-SiC, CaO, MgO, SrS, MgS, SrO
Total Initial Geometries	~100,000	N/A	Single and double defects processed by ADAQ
NV-like Defects Identified	180	Unique Defects	Meeting stability, spin (S ≥ 1), and optical criteria
NV Center (Diamond) ZPL	1.945	eV	Experimental Value
PbV Center (Diamond) ZPL	2.384	eV	Experimental Value
Nac (Diamond) Spin State	1.5 (3/2)	N/A	Neutral charge state (0)
Nac (Diamond) TDM	7.41	Debye	Neutral charge state (0), ADAQ result
SiV Center (Diamond) Spin	0.5 (1/2)	N/A	Negative charge state (-1)
Defect Stability Criterion (ε)	< 30	meV	Maximum distance to the defect hull for classification
Minimum ZPL for NV-like	0.5	eV	Search criterion
Minimum TDM for NV-like	3	Debye	Search criterion
PBE ZPL Underestimation	~0.25	eV	Compared to experimental values in diamond

Selected Diamond Defect Data (Table I & III)

Defect (Config)	Charge	Spin (S)	Calc. ZPL [eV]	Exp. ZPL [eV]	TDM [Debye]	ΔQ [amu^1/2Å]
NV	-1	1.0	1.700	1.945	6.66	0.56
SiV	-1	0.5	*	1.680	*	*
GeV	-1	0.5	*	2.060	*	*
PbV	-1	0.5	2.122	2.384	*	*
Nac	0	1.5	1.49	7.41	0.16
Nac	-1	1.0	1.50	7.27	0.15
Lic Vc	+1	1.0	0.64	4.38	0.41
Kc	-1	1.0	0.59	3.77	0.96

Note: * indicates missing values in the ADAQ database due to defect states below the valence band or TDM restriction in search.

Key Methodologies

The identification of NV-like defects relies on the high-throughput Automatic Defect Analysis and Qualification (ADAQ) database, which employs a rigorous, multi-step computational workflow:

Initial Geometry Generation: ADAQ automatically generates initial defect geometries (single and double defects) based on host material symmetry.
Density Functional Theory (DFT) Screening: Calculations are performed using the Vienna Ab initio Simulation Package (VASP) with Projector Augmented Wave (PAW) pseudopotentials and the Perdew, Burke, and Ernzerhof (PBE) functional.
Charge and Spin State Calculation: The workflow calculates different charge (neutral, ±1) and spin states, determining the most energetically stable configuration.
Defect State Identification: The Inverse Participation Ratio (IPR) is used to confirm that defect states reside within the host material’s band gap.
Thermodynamic Stability Assessment: The concept of the Defect Hull is applied to order defects by stability, with NV-like candidates requiring a distance (ε) of < 30 meV from the hull.
Optical Property Calculation: The Delta Self-Consistent Field (ASCF) method is used to calculate critical optical attributes, including the Zero Phonon Line (ZPL) and the Transition Dipole Moment (TDM).
Final Filtering: Defects are selected based on the combined criteria: stability, high spin (S ≥ 1), ZPL > 0.5 eV, and TDM > 3 Debye.

6CCVD Solutions & Capabilities

The research confirms that the future of quantum technology relies on the precise engineering of point defects in high-quality, wide-bandgap semiconductors, particularly diamond. 6CCVD is uniquely positioned to supply the foundational materials and customization services required to realize these computationally predicted NV-like defects.

Applicable Materials for Replication and Extension

To replicate or extend the research on NV, SiV, GeV, SnV, PbV, and other high-spin defects (Nac, Lic, Kc) in diamond, researchers require substrates with exceptional purity and crystalline quality.

6CCVD Material Solution	Description & Application	Key Feature Alignment
Electronic Grade SCD	Ultra-high purity, low-strain single crystal diamond wafers. Ideal for creating NV centers via nitrogen incorporation during growth or for subsequent ion implantation of Group IV elements (Si, Ge, Sn, Pb).	Minimizes spectral diffusion and maximizes coherence time (T₂). Essential for high-spin, optically active defects.
Optical Grade SCD	High transmission across visible and NIR spectra. Perfect for ZPL and TDM characterization of color centers (e.g., SiV, GeV, which have ZPLs in the visible/near-IR range).	Low absorption and scatter for precise optical readout.
Custom Boron-Doped Diamond (BDD)	SCD or PCD doped with Boron. While the paper focuses on spin-1 defects, BDD is crucial for electrical readout mechanisms (Section IV C) and electrochemical applications.	Enables electrical control and readout protocols, offering alternatives to optical methods.

Customization Potential for Defect Engineering

The realization of defects like SiV, GeV, SnV, and PbV requires precise control over doping, implantation, and post-processing. 6CCVD offers comprehensive customization services to meet the exact specifications derived from high-throughput data.

Custom Dimensions and Thickness: We provide SCD plates/wafers up to 125mm (PCD) and custom thicknesses ranging from 0.1 µm to 500 µm for both SCD and PCD. This supports both thin-film device integration and bulk substrate requirements.
Ultra-Low Roughness Polishing: Achieving high-fidelity optical interfaces and minimizing surface-related strain is critical. 6CCVD guarantees Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD, essential for high Debye-Waller factor defects.
Advanced Metalization Services: The paper discusses the need for electrical readout and device integration. 6CCVD offers in-house deposition of standard and custom metal stacks, including Au, Pt, Pd, Ti, W, and Cu, allowing for direct integration of electrodes for electrical control and sensing applications.
Substrate Preparation: We supply substrates optimized for subsequent ion implantation (e.g., Si, Ge, Sn, Pb) and annealing processes required to form the desired XV centers.

Engineering Support and Consultation

The paper highlights the need for improved experimental recipes (doping concentrations, annealing conditions) to bridge the gap between theoretical predictions (ADAQ) and experimental realization.

In-House PhD Expertise: 6CCVD’s team of material scientists and PhD engineers specializes in MPCVD growth and defect incorporation. We offer consultation on material selection, orientation, and surface termination necessary to replicate or extend the research on NV-like defects in diamond.
Recipe Optimization: We assist researchers in defining the optimal substrate specifications (e.g., nitrogen concentration, crystal orientation) required for specific quantum projects, such as those targeting the telecom band ZPLs (e.g., CIV defect in SiC, mentioned in the paper).
Global Supply Chain: We ensure reliable, global shipping (DDU default, DDP available) of high-value diamond materials, supporting international research efforts.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Point defect for quantum technologies is an emerging research area, with the nitrogen-vacancy (NV) center in diamond at the forefront. However, how rare are defects with NV-like properties? In this Perspective, I highlight the results of NV-like defects across 33 different materials, revealing that they are more common than finding four-leaf clovers. I also discuss expanding the search criteria to identify other defects relevant to quantum technologies. Utilizing point defect databases will be instrumental in assisting researchers in discovering previously unexplored defects suitable for quantum technologies.

Tech Support

Original Source

DOI: https://doi.org/10.1063/5.0289896

References

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