Design of a High-Bandwidth Uniform Radiation Antenna for Wide-Field Imaging with Ensemble NV Color Centers in Diamond

At a Glance

Metadata	Details
Publication Date	2022-06-26
Journal	Micromachines
Authors	Zhiming Li, Zhonghao Li, Zhenrong Shi, Hao Zhang, Yanling Liang
Institutions	North University of China
Citations	4
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Bandwidth NV Center Antenna

Executive Summary

This document analyzes the design and performance of a high-bandwidth, uniform radiation hollow Ω-type antenna optimized for wide-field Optically Detected Magnetic Resonance (ODMR) imaging using ensemble Nitrogen-Vacancy (NV) centers in diamond.

Application Focus: High-precision, wide-field quantum sensing and magnetic field imaging utilizing diamond NV ensemble color centers.
Performance Achievement: Achieved exceptional magnetic field uniformity of 94% across a large 4.4 x 4.4 mm² sensing area, critical for wide-field measurements.
Bandwidth Superiority: Demonstrated a measured bandwidth of 988 MHz, representing an 11.82-fold improvement over traditional straight copper antenna designs (83.6 MHz).
Efficiency Enhancement: The hollow Ω-type design increased normalized radiation contrast (efficiency) by 71.8% compared to a straight copper antenna.
Material Requirement: The experiment relied on high-quality 1b-type Single Crystal Diamond (SCD) precursors (4.5 x 4.5 x 0.5 mm³) with controlled nitrogen doping (100-200 ppm) for subsequent electron irradiation and annealing (850 °C) to create uniform NV ensembles.
6CCVD Value Proposition: 6CCVD specializes in providing the necessary high-purity, low-strain Optical Grade SCD substrates with precise dimensions, crystal orientation ((100)), and superior surface polishing (Ra < 1 nm) required for replicating and scaling this advanced quantum sensing platform.

Technical Specifications

The following table summarizes the critical material parameters and performance metrics achieved in the research.

Parameter	Value	Unit	Context
Diamond Type	1b-type SCD	N/A	Precursor material for NV creation
Diamond Dimensions	4.5 x 4.5 x 0.5	mm³	Standard geometric length
Crystal Orientation	(100)	N/A	Lower surface layer
Nitrogen Concentration	100-200	ppm	Required for ensemble NV formation
Electron Irradiation Dose	9.8 x 10¹⁸	cm^-2	NV creation process
Annealing Temperature	~850	°C	Vacuum annealing for NV formation
Magnetic Field Uniformity	94	%	Over 4.4 x 4.4 mm² area
Antenna Bandwidth (Measured)	988	MHz	Hollow Ω-type antenna
Bandwidth Improvement Factor	11.82	times	Compared to straight copper antenna
Radiation Efficiency Increase	71.8	%	Normalized contrast improvement
S11 Resonance Peak (Measured)	-40.22	dB	At 2.844 GHz
FWHM Standard Deviation	5.61	%	Uniformity metric over sensing area
Substrate Dielectric Constant	3.66	N/A	Rogers dielectric substrate
Substrate Thickness	1.524	mm	Antenna substrate

Key Methodologies

The experiment involved precise material preparation and optimized antenna design parameters to achieve high-performance ODMR sensing.

Diamond Precursor Selection: Used 1b-type single crystal diamond (SCD) with a nitrogen concentration of 100-200 ppm, ensuring sufficient nitrogen vacancies for ensemble NV formation.
Crystal Orientation Control: The lower surface layer was specified to present the (100) crystal direction, crucial for controlling the orientation of the magnetic field components relative to the NV axes.
NV Center Creation: High-energy electron irradiation (10 ± 0.5 MeV) was applied at a dose of 9.8 x 10¹⁸ cm^-2 for 3 hours.
Thermal Processing: Vacuum annealing was performed at a constant temperature of approximately 850 °C for 3 hours to mobilize vacancies and form uniformly distributed NV color centers near the surface.
Antenna Simulation: The hollow Ω-type antenna was designed and optimized using HFSS software.
Antenna Fabrication: A Rogers dielectric substrate (relative dielectric constant 3.66, thickness 1.524 mm) was used, incorporating a rectangular microstrip transmission line feed unit for impedance matching.
Performance Characterization: Bandwidth (S11) was measured using a vector network analyzer (Keysight Technologies N5224A). ODMR signals were measured using a CW-ODMR system to determine FWHM, contrast, and uniformity across the 4.4 x 4.4 mm² area.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced diamond materials necessary to replicate, scale, and extend this high-performance wide-field quantum sensing research.

Applicable Materials

To achieve the high concentration and uniform distribution of NV centers required for wide-field imaging, researchers need high-quality 1b-type diamond precursors.

Research Requirement	6CCVD Material Solution	Key Benefit
1b-type Precursor	Optical Grade Single Crystal Diamond (SCD)	Controlled nitrogen doping (100-200 ppm range available) ensures optimal precursor material for high-density NV ensemble creation.
High Uniformity/Low Strain	High-Purity SCD	Minimizes internal strain, leading to narrower ODMR linewidths (FWHM) and improved coherence times (T₂), essential for high-precision sensing.
Surface Quality	SCD Polished Plates (Ra < 1 nm)	Our standard SCD polishing achieves surface roughness significantly better than the “submicron” requirement, maximizing optical collection efficiency and reducing background noise.

Customization Potential

The success of this wide-field imaging system depends on precise material dimensions and integration capabilities. 6CCVD offers full customization to meet experimental demands.

Custom Dimensions and Thickness: The paper used a 4.5 x 4.5 x 0.5 mm³ sample. 6CCVD can supply SCD plates in custom dimensions up to 500 µm thickness, or thicker Substrates up to 10 mm, ensuring compatibility with existing ODMR setups.
Crystal Orientation Control: We guarantee the required (100) crystal orientation for the sensing surface, critical for controlling the Zeeman splitting and magnetic field projection onto the NV axes.
Scaling Capabilities: For future wide-field applications requiring larger sensing areas, 6CCVD can provide Polycrystalline Diamond (PCD) wafers up to 125 mm in diameter, offering a path for scaling up the antenna and sensing area beyond the 4.4 x 4.4 mm² demonstrated here.
Integrated Microwave Structures: While the antenna was external, future designs may require integrated microwave transmission lines or electrodes directly on the diamond. 6CCVD offers custom metalization services (including Au, Pt, Ti, W, Cu) for creating on-chip microwave structures, bonding pads, or BDD electrodes for enhanced field control.

Engineering Support

The successful creation of uniform NV ensembles requires precise control over the precursor material and subsequent processing steps (irradiation and annealing).

Material Selection Consultation: 6CCVD’s in-house PhD team provides expert consultation on selecting the optimal 1b-type SCD grade, nitrogen concentration, and crystal orientation necessary to replicate or extend this wide-field magnetic imaging research.
Processing Optimization: We assist researchers in defining the material specifications that best support high-energy electron irradiation and 850 °C annealing protocols, ensuring maximum yield of high-quality, near-surface NV centers.
Global Logistics: We offer reliable Global Shipping (DDU default, DDP available) to ensure sensitive quantum materials arrive safely and promptly at research facilities worldwide.

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

View Original Abstract

Radiation with high-efficiency, large-bandwidth, and uniform magnetic field radiation antennas in a large field of view are the key to achieving high-precision wide-field imaging. This paper presents a hollow Ω-type antenna design for diamond nitrogen-vacancy (NV) ensemble color center imaging. The uniformity of the antenna reaches 94% in a 4.4 × 4.4 mm2 area. Compared with a straight copper antenna, the radiation efficiency of the proposed antenna is 71.8% higher, and the bandwidth is improved by 11.82 times, demonstrating the effectiveness of the hollow Ω-type antenna.

Tech Support

Original Source

DOI: https://doi.org/10.3390/mi13071007

References

2017 - High-sensitivity spin-based electrometry with an ensemble of nitrogen-vacancy centers in diamond [Crossref]
2011 - Electric-field sensing using single diamond spins [Crossref]
2013 - High-precision nanoscale temperature sensing using single defects in diamond [Crossref]
2010 - Temperature dependence of the nitrogen-vacancy magnetic resonance in diamond [Crossref]
2018 - Optimization of temperature sensitivity using the optically detected magnetic-resonance spectrum of a nitrogen-vacancy center ensemble [Crossref]
2013 - Stray-field imaging of magnetic vortices with a single diamond spin [Crossref]
2016 - Fabrication of all diamond scanning probes for nanoscale magnetometry [Crossref]
2018 - High-resolution magnetic resonance spectroscopy using a solid-state spin sensor [Crossref]
2014 - Efficient route to high-bandwidth nanoscale magnetometry using single spins in diamond [Crossref]