14N Hyperfine and nuclear interactions of axial and basal NV centers in 4H-SiC - A high frequency (94 GHz) ENDOR study

At a Glance

Metadata	Details
Publication Date	2023-09-28
Journal	Journal of Applied Physics
Authors	Fadis F. Murzakhanov, Margarita A. Sadovnikova, G. V. Mamin, S. S. Nagalyuk, H. J. von Bardeleben
Institutions	Sorbonne Université, Paderborn University
Citations	9
Analysis	Full AI Review Included

Technical Documentation & Analysis: ¹⁴N Hyperfine and Nuclear Interactions in 4H-SiC NV Centers

This document analyzes the research article “¹⁴N Hyperfine and nuclear interactions of axial and basal NV centers in 4H-SiC: A high frequency (94 GHz) ENDOR study” (J. Appl. Phys. 134, 123906 (2023)). The analysis focuses on extracting key technical data and leveraging 6CCVD’s capabilities in MPCVD diamond growth to support and extend this advanced quantum research.

Executive Summary

The following is a high-density summary of the research findings and 6CCVD’s core value proposition for quantum technology applications:

Core Achievement: Determined the complete spin-Hamiltonian parameters (Hyperfine Interaction, HFI, and Nuclear Quadrupole Interaction, NQI) for all four inequivalent Nitrogen-Vacancy (NV) center configurations (NV_kk, NV_hh, NV_hk, NV_kh) in 4H-SiC.
Methodology: Utilized high-frequency (94 GHz) Electron-Nuclear Double Resonance (ENDOR) spectroscopy combined with Density Functional Theory (DFT) calculations to achieve kHz resolution necessary for resolving weak interactions.
Quantum Relevance: The precise knowledge of electron-nuclear interaction parameters is critical for establishing quantum protocols, specifically for polarization transfer from the electron spin to the ¹⁴N nuclear spin, enabling quantum memory nodes.
Key Finding: Observed differences in HFI and NQI parameters between the four NV configurations, rationalized by subtle distinctions in local atomic structure, suggesting each configuration may act as a separate optically addressable qubit.
6CCVD Value Proposition: While SiC NV centers are promising, the ultimate performance metrics (ultra-long coherence times, T₂) are achieved using the NV^- center in Single Crystal Diamond (SCD).
Sales Driver: 6CCVD supplies ultra-high purity SCD substrates, ready for precise ion implantation and annealing, offering the superior material platform required to extend this foundational research into scalable, high-coherence quantum devices.

Technical Specifications

The following table summarizes the critical experimental and derived data points from the research:

Parameter	Value	Unit	Context
Host Material Polytype	4H-SiC	N/A	Commercial n-type bulk crystal
Initial Nitrogen Concentration	2 x 10¹⁷	cm^-3	Sample doping level
Irradiation Particle	Proton	N/A	Used for V_Si defect generation
Irradiation Energy	12	MeV	High-energy proton source
Irradiation Fluence	1 x 10¹⁶	cm^-2	Dose used for defect creation
Annealing Temperature	900	°C	Optimal temperature for NV formation
Spectrometer Frequency	94 (W-band)	GHz	ESE ESR/ENDOR measurement frequency
Measurement Temperature	150	K	Experimental temperature
NV_hh Quadrupole Splitting (P)	1.89 (± 0.05)	MHz	Nuclear Quadrupole Interaction (NQI)
NV_hh Hyperfine Constant (A_\|\|)	-1.165	MHz	Axial Electron-Nuclear HFI
NV_kk Quadrupole Splitting (P)	1.81	MHz	Axial NQI (slightly smaller than NV_hh)
NV_kk Hyperfine Constant (A_\|\|)	1.14	MHz	Axial HFI (slightly smaller than NV_hh)
NV_kh Hyperfine Constant (A_\|\|)	-1.05	MHz	Basal HFI
NV_hk Hyperfine Constant (A_\|\|)	-0.87	MHz	Basal HFI

Key Methodologies

The experimental approach combined material processing (defect generation) with advanced high-frequency spectroscopy and computational modeling:

Substrate Selection: Used commercial n-type, (0001) face 4H-SiC bulk crystal with a native nitrogen concentration of 2 x 10¹⁷ cm^-3.
Defect Creation: Silicon vacancies (V_Si) were generated via high-energy (12 MeV) proton irradiation at a fluence of 1 x 10¹⁶ cm^-2.
NV Center Formation: Thermal annealing was performed at T = 900 °C, allowing mobile V_Si defects to complex with carbon-substituted nitrogen atoms, forming stable NV centers (NV_CV_Si).
ESR Detection: Electron Spin Echo-Detected (ESE) ESR measurements were conducted at W-band (94 GHz) and T = 150 K to establish the resonance magnetic fields of the fine structure transitions.
ENDOR Spectroscopy: Pulsed ENDOR measurements utilized a Mims-pulse sequence (π/2 - τ - π - T - π/2 - RF π-pulse - π/2 - ESE) to measure NMR transitions with kHz resolution, allowing precise determination of HFI and NQI parameters.
Computational Modeling (DFT): Density Functional Theory (DFT) using the PBE functional and GIPAW module was employed to calculate ¹⁴N electron-nuclear coupling parameters and rationalize the observed differences based on local atomic structure deviations.

6CCVD Solutions & Capabilities

This research provides foundational data for solid-state qubits. While SiC is a viable platform, the highest performance quantum memory and sensing applications rely on the superior coherence properties of the NV center in diamond. 6CCVD is uniquely positioned to supply the necessary materials and processing capabilities to advance this research using the diamond platform.

Applicable Materials & Requirements	6CCVD Solution & Capability	Engineering Advantage
High-Coherence Qubit Platform	Optical Grade Single Crystal Diamond (SCD): SCD grown via MPCVD with ultra-low native nitrogen (< 1 ppb) and minimal strain.	Provides the longest known spin coherence times (T₂), essential for extending quantum protocols beyond SiC limitations.
Precise Defect Generation	Custom SCD Substrates for Implantation: SCD plates (0.1 µm to 500 µm thickness) optimized for external ion implantation (e.g., ¹⁴N or ¹⁵N) to control NV density and depth.	Enables deterministic creation of single NV centers or high-density ensembles, replicating the defect generation methodology used in the SiC study.
Large-Scale Device Development	Large Format PCD Wafers: Polycrystalline Diamond (PCD) plates up to 125 mm diameter, suitable for scalable quantum sensor arrays or high-throughput processing.	Offers a cost-effective, large-area alternative for applications where ensemble coherence (T₂*) is sufficient.
Integration of MW Control Structures	In-House Custom Metalization: Internal capability to deposit thin films (Au, Pt, Pd, Ti, W, Cu) for creating microwave striplines or electrodes required for high-frequency (94 GHz) ENDOR/ESR setups.	Ensures robust, high-quality metal contacts necessary for efficient MW delivery and coherent spin control.
Optimized Optical Readout	Precision Polishing Services: SCD substrates polished to Ra < 1 nm, ensuring minimal surface roughness for high-efficiency optical readout (PL/ODMR) and integration with nanophotonic structures.	Reduces scattering losses, critical for maximizing the signal-to-noise ratio in single-qubit experiments.
Material Optimization for HFI/NQI Studies	Boron-Doped Diamond (BDD): Available for electrochemistry or specific charge state control studies, offering a complementary material platform for quantum research.	Allows researchers to explore the impact of doping on NV charge state stability and local electric fields (EFG), relevant to NQI parameters.

Engineering Support

6CCVD’s in-house PhD team specializes in optimizing MPCVD growth parameters to control impurity incorporation (e.g., nitrogen, boron) and minimize strain, which directly impacts the Zero-Field Splitting (ZFS) and coherence times of solid-state defects. We can assist researchers transitioning from SiC to diamond or optimizing diamond recipes for similar NV Center Hyperfine Interaction projects.

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

View Original Abstract

The nitrogen-vacancy (NV) centers (NCVSi)− in 4H silicon carbide (SiC) constitute an ensemble of spin S = 1 solid state qubits interacting with the surrounding 14N and 29Si nuclei. As quantum applications based on a polarization transfer from the electron spin to the nuclei require the knowledge of the electron-nuclear interaction parameters, we have used high-frequency (94 GHz) electron-nuclear double resonance spectroscopy combined with first-principles density functional theory to investigate the hyperfine and nuclear quadrupole interactions of the basal and axial NV centers. We observed that the four inequivalent NV configurations (hk, kh, hh, and kk) exhibit different electron-nuclear interaction parameters, suggesting that each NV center may act as a separate optically addressable qubit. Finally, we rationalized the observed differences in terms of distinctions in the local atomic structures of the NV configurations. Thus, our results provide the basic knowledge for an extension of quantum protocols involving the 14N nuclear spin.

Tech Support

Original Source

DOI: https://doi.org/10.1063/5.0170099

References

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2018 - Quantum technologies with optically interfaced solid-state spins [Crossref]
2021 - Quantum computer based on color centers in diamond [Crossref]
2022 - Silicon carbide photonics bridging quantum technology [Crossref]
2023 - NV-centers in SiC: A solution for quantum computing technology? [Crossref]
2018 - Deterministic delivery of remote entanglement on a quantum network [Crossref]
2014 - Nitrogen-vacancy centers in diamond: Nanoscale sensors for physics and biology [Crossref]
2019 - Zero-field magnetometry based on nitrogen-vacancy ensembles in diamond [Crossref]
2017 - Observation of discrete time-crystalline order in a disordered dipolar many-body system [Crossref]