Spin coherence and 14 N ESEEM effects of nitrogen-vacancy centers in diamond with X-band pulsed ESR

At a Glance

Metadata	Details
Publication Date	2016-12-20
Journal	Diamond and Related Materials
Authors	Brendon C. Rose, Christoph Weis, Alexei M. Tyryshkin, T. Schenkel, S. A. Lyon
Institutions	Technische Universität Ilmenau, Lawrence Berkeley National Laboratory
Citations	15
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Coherence NV Centers in MPCVD Diamond

This document analyzes the research paper “Spin Coherence and ¹⁴N ESEEM Effects of Nitrogen-Vacancy Centers in Diamond with X-band Pulsed ESR” to highlight key technical requirements and demonstrate how 6CCVD’s specialized MPCVD diamond materials and services can accelerate and scale similar quantum research applications.

Executive Summary

The research successfully demonstrates the creation and characterization of high-quality Nitrogen-Vacancy (NV^-) ensembles in synthetic Type IIb CVD diamond, achieving long spin coherence times critical for quantum technologies.

Material Requirement: High-purity, low-nitrogen concentration (< 1 ppm) synthetic CVD diamond is essential for achieving long electron spin coherence.
Critical Process Step: A high-temperature, long-duration post-radiation anneal (1000 °C for 60 minutes) is proven necessary to repair electron irradiation damage and restore maximum spin coherence (T₂).
Key Achievement: An electron spin coherence time of T₂ = 0.74 ms at 5 K was achieved, limited only by the natural abundance (1.1%) of ¹³C nuclear spectral diffusion.
Advanced Characterization: X-band Pulsed ESR and ESEEM techniques were used to accurately determine the ¹⁴N hyperfine and quadrupole tensors, confirming the high structural quality of the NV centers.
Proximity Analysis: ESEEM resolved hyperfine couplings from proximal ¹³C sites (second and fourth nearest neighbors), providing crucial data for quantum control schemes.
6CCVD Value Proposition: 6CCVD provides the necessary ultra-high purity Single Crystal Diamond (SCD) starting material, custom dimensions, and advanced polishing/metalization services required to replicate and scale these high-coherence quantum platforms.

Technical Specifications

The following hard data points were extracted from the experimental section, detailing the material properties and achieved performance metrics.

Parameter	Value	Unit	Context
Base Material Type	Type IIb (P2 grade)	N/A	Synthetic CVD diamond
Initial Nitrogen Concentration ([N])	< 1	ppm	Pristine material (ElementSix)
¹³C Isotopic Abundance	1.1	%	Natural abundance
Electron Irradiation Energy	2	MeV	To generate vacancies
Highest Irradiation Dose (Samples C, D)	10¹⁷	cm^-2	For high NV concentration
Optimal Annealing Temperature	1000	°C	Required for damage repair
Optimal Annealing Time	60	mins	Required for T₂ recovery
Achieved Spin Coherence Time (T₂)	0.74 ± 0.01	ms	At 5 K (Sample C), limited by ¹³C
ESR Measurement Band	X-band	N/A	9.6 GHz
Magnetic Field Range (B₀)	280 - 400	mT	Pulsed ESR experiments
Activation Energy (Residual Damage)	2.5	meV	Deduced from T₂ temperature dependence (Sample B)
¹⁴N Hyperfine Tensor (A_\|\|)	-2.19(2)	MHz	Derived from FT-ESEEM spectra
¹³C Hyperfine Coupling (A₁)	2.56(2)	MHz	Fourth nearest-neighbor site

Key Methodologies

The experimental success hinges on precise material preparation and advanced pulsed ESR techniques.

Material Selection: Use of synthetic Type IIb CVD diamond (P2 grade) with ultra-low nitrogen concentration ([N] < 1 ppm) to minimize decoherence from P1 centers.
Vacancy Generation: High-energy electron irradiation (2 MeV) was applied to displace carbon atoms and create vacancies necessary for NV^- formation.
Initial Annealing: Samples were initially annealed in a nitrogen atmosphere at 900 °C for 20 minutes.
Damage Repair and NV Formation: A critical secondary anneal was performed in forming gas at 1000 °C for 60 minutes to mobilize vacancies, trap them at substitutional nitrogen sites (forming NV centers), and repair residual radiation damage.
Spin Polarization: Optical pumping was achieved using a frequency-doubled YLF laser (523 nm) to achieve steady-state spin polarization of the NV centers.
Coherence Measurement: Two-pulse (Hahn) echo experiments were performed using X-band Pulsed ESR (9.6 GHz) at low temperatures (2-70 K) to measure T₂.
Nuclear Coupling Analysis: Electron Spin Echo Envelope Modulation (ESEEM) was used to resolve the hyperfine and quadrupole couplings of the central ¹⁴N nucleus and proximal ¹³C nuclei.

6CCVD Solutions & Capabilities

This research confirms that the foundation of high-performance NV-based quantum devices is ultra-high purity, low-defect CVD diamond. 6CCVD is uniquely positioned to supply the necessary materials and customization services to advance this work from fundamental research to scalable device integration.

Applicable Materials

To replicate and extend the T₂ coherence times achieved in this paper, researchers require the highest quality SCD with minimal paramagnetic impurities.

6CCVD Material Recommendation	Specification	Application Context
Optical Grade SCD	Nitrogen < 0.05 ppm (typical)	Essential starting material for maximizing T₂ coherence time by minimizing P1 center spectral diffusion.
Isotopically Purified SCD	¹²C enrichment > 99.99%	To surpass the T₂ limit (0.74 ms) imposed by natural ¹³C abundance, enabling T₂ times in the millisecond range and beyond.
Custom Substrates	Up to 10 mm thickness	For robust thermal management and mechanical stability in high-power ESR/ODMR setups.

Customization Potential for Device Integration

The next phase of NV research involves integrating these centers into functional quantum devices, requiring precise material engineering that 6CCVD specializes in.

Custom Service	6CCVD Capability	Research Benefit
Polishing & Surface Quality	SCD: Ra < 1 nm (Ultra-low roughness)	Critical for minimizing surface defects that cause decoherence and for integrating optical waveguides or resonators (e.g., for ODMR).
Custom Dimensions	Plates/wafers up to 125 mm (PCD)	Enables scaling from small research samples to wafer-level processing for commercial quantum chip fabrication.
Metalization Services	Au, Pt, Pd, Ti, W, Cu (In-house)	Required for creating microwave antennas (coplanar waveguides) or electrical contacts necessary for pulsed ESR/ODMR device operation.
Laser Cutting & Shaping	Precision shaping and dicing	Allows for the creation of custom geometries (e.g., micro-pillars, cantilevers) for enhanced spin readout or strain engineering.

Engineering Support

6CCVD’s in-house PhD team provides authoritative support to ensure optimal material selection and processing compatibility.

NV Creation Optimization: Our experts can assist researchers in selecting the ideal starting material purity and thickness to optimize the subsequent electron irradiation and high-temperature annealing steps (1000 °C, 60 mins) required for maximizing NV yield and T₂ coherence.
Decoherence Mitigation: We consult on material specifications (e.g., isotopic purity, surface termination) to mitigate environmental contributions to spin decoherence, such as the ¹³C spectral diffusion identified as the limiting factor in this study.
Global Logistics: We offer reliable global shipping (DDU default, DDP available) to ensure rapid delivery of high-value materials worldwide.

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

Tech Support

Original Source

DOI: https://doi.org/10.1016/j.diamond.2016.12.009

References

2010 - Spin-light coherence for single-spin measurement and control in diamond [Crossref]
2006 - Room-temperature coherent coupling of single spins in diamond [Crossref]
2011 - Magnetic field imaging with nitrogen-vacancy ensembles [Crossref]
2011 - Quantum control of proximal spins using nanoscale magnetic resonance imaging [Crossref]
2011 - Electric-field sensing using single diamond spins [Crossref]
2008 - Nanoscale magnetic sensing with an individual electronic spin in diamond [Crossref]
2008 - High-sensitivity diamond magnetometer with nanoscale resolution [Crossref]
1997 - Scanning confocal optical microscopy and magnetic resonance on single defect centers [Crossref]
2006 - Processing quantum information in diamond [Crossref]
2006 - Coherent dynamics of coupled electron and nuclear spin Qubits in diamond [Crossref]