Integration of High-Brightness QLED-Excited Diamond Magnetic Sensor

At a Glance

Metadata	Details
Publication Date	2025-09-04
Journal	Micromachines
Authors	Pengfei Zhao, Jiangbing Du, Jinyu Tai, Zhong-Xia Shang, Xia Yuan
Institutions	North University of China
Analysis	Full AI Review Included

Technical Documentation & Analysis: QLED-Excited Diamond Magnetic Sensor Arrays

This document analyzes the research on integrating high-brightness Quantum-Dot Light-Emitting Diodes (QLEDs) with Nitrogen-Vacancy (NV) center diamond sensors to create scalable magnetometer arrays. This innovation directly addresses the limitations of traditional bulk laser excitation systems, paving the way for highly integrated quantum sensing platforms.

Executive Summary

The integration of QLEDs with NV center diamond marks a significant advancement in scalable quantum magnetometry, overcoming major hurdles related to size, cost, and integration complexity associated with conventional 532 nm laser systems.

Breakthrough Integration: A 2x2 monolithically integrated NV center magnetometer array was successfully fabricated, utilizing QLEDs as the high-brightness, micro-fabrication compatible excitation source.
Scalability & Miniaturization: The QLED light source reduces the excitation volume dramatically (from approximately 142.5 x 60 x 50 mm for a traditional laser to 1.5 x 1.5 x 0.2 mm for a single QLED unit).
High Sensitivity Achieved: The array units demonstrated a magnetic sensitivity consistently below 26 nT·Hz^-1/2 (best unit at 22.8 nT·Hz^-1/2).
Operational Performance: The system achieved an effective measurable range of ±120 µT within the critical 1-10 Hz effective bandwidth, suitable for near-DC magnetic field measurements.
Core Functionality Validated: The array successfully demonstrated the ability to simultaneously resolve multi-regional static magnetic fields and track dynamic field orientations in real-time.
Material Requirement: The success relies on high-quality Single Crystal Diamond (SCD) substrates with controlled NV center orientation (<111> axis) for optimal single-axis ODMR isolation.

Technical Specifications

The following hard data points were extracted from the experimental validation of the QLED-NV magnetometer array prototype:

Parameter	Value	Unit	Context
Magnetic Sensitivity (Best)	22.8	nT·Hz^-1/2	Measured within the 1-10 Hz effective bandwidth.
Magnetic Sensitivity (Range)	22.8 to 25.6	nT·Hz^-1/2	Consistency across the four M1-M4 units.
Effective Measurable Range	±120	µT	Harmonized linear range across the array units.
Effective Bandwidth	1-10	Hz	Range selected to reflect practical near-DC measurements.
NV Center Orientation	<111>	Axis	Selected for single-axis ODMR signal isolation.
Bias Magnetic Field (B)	3	mT	Applied parallel to the <111> axis for Zeeman splitting.
Microwave Resonance Frequency	2.788	GHz	Fixed operating frequency for CW-ODMR detection.
QLED Emission Wavelength	532	nm	Precisely matched to the NV center excitation energy level.
QLED FWHM	20	nm	Narrow full width at half maximum for efficient excitation.
QLED Luminance Range	38,000 to 42,000	cd m^-2	Luminance achieved at 5 V bias.
Single QLED Unit Volume	1.5 x 1.5 x 200	mm x mm x µm	QLED light source volume (dramatically miniaturized).

Key Methodologies

The experimental success hinges on precise material preparation and integration techniques, particularly concerning the QLED fabrication and the Optically Detected Magnetic Resonance (ODMR) setup.

Diamond Substrate Selection: High-quality diamond with Nitrogen-Vacancy (NV) centers was used. Specifically, <111>-axis NV center diamond was selected to isolate single-axis ODMR signals, maximizing magnetic influence along the desired orientation.
QLED Fabrication: Devices were prepared via the mature spin-coating method on low-resistivity (6-8 Ω/sq) Indium Tin Oxide (ITO) anode substrates.
Thin-Film Deposition: Functional layers (PEDOT:PSS, TFB, QDs, ZnMgO) were spin-coated and deposited at a speed of 1500 r/min, followed by patterned Aluminum (Al) electrode evaporation using a graphical mask.
Monolithic Integration: The 2x2 QLED array was integrated with photodetectors, filters, the diamond substrate, and a large-area antenna using UV-curable resin (UV glue) encapsulation.
Magnetic Field Detection Technique: Continuous-Wave Optically Detected Magnetic Resonance (CW-ODMR) was employed, integrated with lock-in detection to enhance system stability and signal-to-noise ratio.
ODMR Operating Parameters: A fixed bias magnetic field of B = 3 mT was applied. The microwave signal was modulated at 500 Hz (1 V amplitude) and fixed at the single-peak valley position (approximately 2.788 GHz).
Sensitivity Calculation: Magnetic Noise Spectral Density (ASD) was derived from system background noise collected over 1 hour, focusing on the 1-10 Hz range to reflect practical near-DC sensitivity, avoiding 1/f noise effects.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the foundational diamond materials and advanced processing required to replicate and scale this QLED-NV magnetometer array technology for commercial or large-scale research deployment.

Applicable Materials

To replicate or extend this research, high-quality diamond materials are essential:

Optical Grade Single Crystal Diamond (SCD): Required for stable, high-contrast NV center formation. 6CCVD supplies SCD wafers with low defect density, crucial for achieving the reported nT-level sensitivity.
Custom <111> SCD Substrates: The paper explicitly used <111>-axis NV centers to isolate single-axis ODMR signals. 6CCVD offers custom SCD growth and processing tailored to specific crystallographic orientations, ensuring optimal alignment for vector magnetometry.
SCD Thickness Control: We provide SCD layers ranging from 0.1 µm up to 500 µm, allowing researchers to precisely control the NV center depth relative to the QLED excitation source for maximum efficiency.

Customization Potential

The integration of the QLED array demands precise material handling and micro-fabrication compatibility, areas where 6CCVD excels:

Research Requirement	6CCVD Solution & Capability	Technical Advantage
Array Scaling & Dimensions	Custom Dimensions up to 125mm.	6CCVD supplies large-area Polycrystalline Diamond (PCD) plates (up to 125mm) and custom-sized SCD wafers, enabling the scaling of the 2x2 prototype into high-density, large-format arrays for high-resolution field mapping.
Surface Quality	Ultra-Low Roughness Polishing (Ra < 1 nm).	Our precision polishing services achieve surface roughness (Ra) below 1 nm on SCD, minimizing optical scattering and ensuring efficient coupling between the QLED (532 nm) and the diamond surface.
Electrode Integration	In-House Metalization Services.	6CCVD offers custom metalization stacks (Au, Pt, Pd, Ti, W, Cu). These capabilities are vital for fabricating the robust microwave antenna structures and electrodes necessary for array operation and integration with micro-fabrication processes.
Global Logistics	Global Shipping (DDU/DDP).	We ensure reliable, global delivery of sensitive quantum materials, simplifying the supply chain for international research teams.

Engineering Support

6CCVD’s in-house PhD team specializes in MPCVD diamond growth and post-processing for quantum applications. We can assist researchers with material selection, NV creation optimization, and surface preparation for similar QLED-NV Magnetometer Array projects, ensuring the diamond substrate meets the stringent requirements for high-sensitivity ODMR detection.

Call to Action: For custom specifications or material consultation regarding high-quality SCD substrates for scalable quantum sensing arrays, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

The nitrogen-vacancy (NV) center magnetic sensor, leveraging nitrogen-vacancy quantum effects, enables high-sensitivity magnetic field detection via optically detected magnetic resonance (ODMR). However, conventional single-point integrated devices suffer from limitations such as inefficient regional magnetic field detection and challenges in discerning the directional variations of dynamic magnetic fields. To address these issues, this study proposes an array- based architecture that innovatively substitutes the conventional 532 nm laser with quantum-dot light-emitting diodes (QLEDs). Capitalizing on the advantages of QLEDs—including compatibility with micro/nano-fabrication processes, wavelength tunability, and high luminance—a 2 × 2 monolithically integrated magnetometer array was developed. Each sensor unit achieves a magnetic sensitivity of below 26 nT·Hz−1/2 and a measurable range of ±120 μT within the 1-10 Hz effective bandwidth. Experimental validation confirms the array’s ability to simultaneously resolve multi-regional magnetic fields and track dynamic field orientations while maintaining exceptional device uniformity. This advancement establishes a scalable framework for the design of large-scale magnetic sensing arrays, demonstrating significant potential for applications requiring spatially resolved and directionally sensitive magnetometry.

Tech Support

Original Source

DOI: https://doi.org/10.3390/mi16091021

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