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Nitrogen-Related High-Spin Vacancy Defects in Bulk (SiC) and 2D (hBN) Crystals - Comparative Magnetic Resonance (EPR and ENDOR) Study

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2024-06-14
JournalQuantum Reports
AuthorsЛароса Đ›Đ°Ń‚Ń‹ĐżĐŸĐČĐ°, Fadis F. Murzakhanov, G. V. Mamin, Margarita A. Sadovnikova, H. J. von Bardeleben
InstitutionsSorbonne Université, Institut des NanoSciences de Paris
Citations3
AnalysisFull AI Review Included

Technical Documentation & Analysis: High-Spin Vacancy Defects in SiC and hBN

Section titled “Technical Documentation & Analysis: High-Spin Vacancy Defects in SiC and hBN”

This document analyzes the research paper “Nitrogen-Related High-Spin Vacancy Defects in Bulk (SiC) and 2D (hBN) Crystals: Comparative Magnetic Resonance (EPR and ENDOR) Study” and outlines how 6CCVD’s advanced MPCVD diamond materials and processing capabilities can support and extend this critical quantum information research.

Executive Summary

Section titled “Executive Summary”

This research provides a crucial comparative analysis of high-spin vacancy defects (potential solid-state qubits) in two distinct material platforms: bulk 4H-SiC (Nitrogen Vacancy, NV⁻) and 2D hexagonal Boron Nitride (Boron Vacancy, VB⁻).

  • Core Achievement: Successful characterization of spin-optical, electron-nuclear, and relaxation properties of NV⁻ in SiC and VB⁻ in hBN using high-frequency (94 GHz) pulsed EPR and ENDOR spectroscopy.
  • Coherence Comparison: The NV⁻ center in 4H-SiC demonstrated significantly superior spin-spin coherence time (T2 = 50 ”s at 10 K) compared to the VB⁻ center in hBN (T2 = 15 ”s at 10 K).
  • Material Dependence: Key spin Hamiltonian parameters (Zero-Field Splitting D, Hyperfine Azz) were shown to be highly dependent on the material matrix (3D bulk vs. 2D van der Waals structure).
  • Qubit Manipulation: Rabi oscillations were successfully registered, qualitatively demonstrating the potential of both defects as electron qubits, with damping times TR of 2.2 ”s (NV⁻) and 5.5 ”s (VB⁻).
  • Room Temperature Feasibility: The study confirmed that the long T1 time (100 ”s) of NV⁻ in SiC at 297 K is sufficient for observing ENDOR signals, paving the way for room-temperature quantum registers.
  • Applied Conclusion: The findings underscore the necessity of selecting the optimal material platform (e.g., SCD diamond, SiC) based on the required coherence and relaxation properties for developing robust quantum registers.

Technical Specifications

Section titled “Technical Specifications”

The following hard data points were extracted from the comparative study of the spin Hamiltonian and dynamic characteristics of the defects.

ParameterValueUnitContext
Zero-Field Splitting (D)1.3GHzNV⁻ center in 4H-SiC
Zero-Field Splitting (D)3.6GHzVB⁻ center in hBN
Axial Hyperfine (Azz)1.1MHzNV⁻ center in 4H-SiC
Axial Hyperfine (Azz)85MHzVB⁻ center in hBN
Quadrupole Coupling (CQ)2.53MHzNV⁻ center in 4H-SiC
Quadrupole Coupling (CQ)2.11MHzVB⁻ center in hBN
Spin-Spin Relaxation (T2)50”sNV⁻ center in 4H-SiC (10 K)
Spin-Spin Relaxation (T2)15”sVB⁻ center in hBN (10 K)
Spin-Lattice Relaxation (T1)500msNV⁻ center in 4H-SiC (10 K)
Spin-Lattice Relaxation (T1)100”sNV⁻ center in 4H-SiC (297 K)
Rabi Damping Time (TR)2.2”sNV⁻ center in 4H-SiC (10 K)
EPR Measurement Frequency94GHzW-band spectroscopy
Magnetic Field (B0)3.4THigh-field Zeeman interaction

Key Methodologies

Section titled “Key Methodologies”

The experiment relied on precise material engineering and advanced high-frequency magnetic resonance techniques to characterize the spin defects.

  1. SiC Sample Preparation:
    • Commercial N-doped 4H-SiC single crystals (2 x 1017 cm-3) were used.
    • Irradiation: 12 MeV protons at 295 K with a total fluence of 1 x 1016 cm-2 to create Si vacancies.
    • Annealing: Subsequent thermal treatment at 900 °C to facilitate Si vacancy diffusion and form VSiNC complexes (NV⁻ centers).
  2. hBN Sample Preparation:
    • Commercial hBN single crystals were used.
    • Irradiation: 2 MeV electrons at room temperature with a total dose of 6 x 1018 cm-2 to create VB⁻ defects. No annealing was applied.
  3. Spectroscopy Setup:
    • Measurements were conducted using a W-band (94 GHz) Bruker Elexsys E680 pulsed EPR spectrometer.
    • A cylindrical dielectric resonator (3 mm characteristic dimension) was used to maximize the filling factor.
  4. Optical Excitation:
    • Photoinduced EPR and ENDOR utilized a 532 nm green laser (up to 200 mW output power) for effective spin polarization and population inversion.
  5. Dynamic Measurements:
    • Relaxation times (T1, T2) were determined using standard pulse sequences (Inversion-Recovery and Hahn echo sequences).
    • Rabi oscillations were measured to assess quantum manipulation capability.
  6. ENDOR Spectroscopy:
    • Electron-Nuclear Double Resonance (ENDOR) was performed using the Mims pulse sequence combined with a 150 kW RF generator (0.5-200 MHz) to resolve hyperfine and quadrupole interactions, crucial for nuclear spin readout.

6CCVD Solutions & Capabilities

Section titled “6CCVD Solutions & Capabilities”

The research highlights the critical role of material quality and precise defect engineering in achieving functional solid-state qubits. While this paper focuses on SiC and hBN, 6CCVD specializes in the benchmark material for high-coherence quantum systems: MPCVD Diamond.

Applicable Materials: The Diamond Advantage

Section titled “Applicable Materials: The Diamond Advantage”

To replicate or significantly extend the coherence results achieved in SiC, researchers require the superior material purity and structural perfection offered by Single Crystal Diamond (SCD).

  • Optical Grade SCD: For achieving maximum coherence times (T2 > 1 ms), 6CCVD provides high-purity SCD wafers with extremely low native nitrogen content. This allows for precise, controlled introduction of NV⁻ centers via ion implantation or in-situ doping, minimizing the nuclear spin bath that limits T2 in SiC (T2 = 50 ”s).
  • Controlled Doping: We offer SCD with controlled nitrogen incorporation (up to 100 ppm) necessary for creating high-density NV⁻ ensembles, or low-nitrogen SCD for single-qubit applications.
  • Boron-Doped Diamond (BDD): For exploring alternative spin defects or creating integrated quantum circuits, 6CCVD supplies highly conductive BDD films, suitable for creating microwave structures directly on the diamond substrate.

Customization Potential for Quantum Registers

Section titled “Customization Potential for Quantum Registers”

The complexity of the EPR/ENDOR setup and the need for high-quality, precisely sized samples align perfectly with 6CCVD’s custom fabrication services.

Research Requirement6CCVD CapabilityTechnical Advantage
Custom Sample DimensionsPrecision laser cutting and dicing of SCD/PCD wafers.We supply plates and wafers up to 125mm (PCD) and custom-cut samples (e.g., 0.8 mm x 0.4 mm x 0.2 mm used in the paper) to fit specific resonator cavities (e.g., 450 ”m inner radius quartz capillaries).
Surface QualitySCD polishing to Ra < 1 nm.Essential for minimizing surface defects and ensuring high-fidelity optical coupling (532 nm laser) and low decoherence rates for near-surface qubits.
Integrated Microwave CircuitsInternal metalization services (Au, Pt, Pd, Ti, W, Cu).We can deposit Ti/Pt/Au contact layers directly onto the SCD surface, enabling the fabrication of coplanar waveguides (CPWs) or microwave antennas necessary for efficient 94 GHz microwave excitation and Rabi oscillation control.
Defect EngineeringSCD substrates up to 500 ”m thick, suitable for high-energy ion implantation (protons/electrons) and high-temperature annealing (up to 1500 °C) required for NV⁻ formation.Provides robust, high-thermal-conductivity substrates capable of withstanding the high-dose irradiation and annealing processes necessary to create stable, uniform defect ensembles.

Engineering Support

Section titled “Engineering Support”

The successful creation of high-spin color centers requires deep expertise in material growth, defect creation, and thermal processing (annealing up to 900 °C, as used for SiC).

6CCVD’s in-house PhD team specializes in MPCVD growth and post-processing techniques for diamond and related wide-bandgap semiconductors. We offer consultation on:

  • Material Selection: Guiding researchers in choosing the optimal SCD grade (e.g., high-purity vs. controlled nitrogen) for specific EPR/ENDOR Spectroscopy or Quantum Sensing applications.
  • Defect Creation Recipes: Assisting with optimizing annealing temperatures and times to maximize the yield and stability of desired spin defects (e.g., NV⁻ centers).
  • Integration: Designing custom metalization schemes for integrating quantum registers into high-frequency (W-band) microwave systems.

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

View Original Abstract

The distinct spin, optical, and coherence characteristics of solid-state spin defects in semiconductors have positioned them as potential qubits for quantum technologies. Both bulk and two-dimensional materials, with varying structural properties, can serve as crystalline hosts for color centers. In this study, we conduct a comparative analysis of the spin-optical, electron-nuclear, and relaxation properties of nitrogen-bound vacancy defects using electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) techniques. We examine key parameters of the spin Hamiltonian for the nitrogen vacancy (NV−) center in 4H-SiC: D = 1.3 GHz, Azz = 1.1 MHz, and CQ = 2.53 MHz, as well as for the boron vacancy (VB−) in hBN: D = 3.6 GHz, Azz = 85 MHz, and CQ = 2.11 MHz, and their dependence on the material matrix. The spin-spin relaxation times T2 (NV− center: 50 ”s and VB−: 15 ”s) are influenced by the local nuclear environment and spin diffusion while Rabi oscillation damping times depend on crystal size and the spatial distribution of microwave excitation. The ENDOR absorption width varies significantly among color centers due to differences in crystal structures. These findings underscore the importance of selecting an appropriate material platform for developing quantum registers based on high-spin color centers in quantum information systems.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2013 - Quantum Computing with Defects [Crossref]
  2. 2010 - Quantum Computing with Defects [Crossref]
  3. 2023 - Quantum Computing Is Scalable on a Planar Array of Qubits with Fabrication Defects [Crossref]
  4. 2018 - Defects in Quantum Computers [Crossref]
  5. 2021 - Quantum Guidelines for Solid-State Spin Defects [Crossref]
  6. 2013 - The Nitrogen-Vacancy Colour Centre in Diamond [Crossref]
  7. 2014 - Nitrogen-Vacancy Centers in Diamond: Nanoscale Sensors for Physics and Biology [Crossref]
  8. 2022 - Coupling a Single NV Center to a Superconducting Flux Qubit via a Nanomechanical Resonator [Crossref]
  9. 2023 - Efficient Scheme for Implementing a Hybrid Toffoli Gate with Two NV Ensembles Simultaneously Controlling a Single Superconducting Qubit [Crossref]
  10. 2018 - Characterizing Quantum Supremacy in Near-Term Devices [Crossref]

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