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6CCVD Research

Ultrasensitive and Reliable Diamond MEMS Magnetic Force Sensor with 3D Imaging at Room Temperature

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2025-05-12
JournalAdvanced Materials Technologies
AuthorsZilong Zhang, Keyun Gu, Zhijian Zhao, Zhibin Lei, Yi‐Hsiu Kao
InstitutionsNational Institute for Materials Science, Tohoku University
AnalysisFull AI Review Included

Technical Documentation & Analysis: Ultrasensitive Diamond MEMS Magnetic Force Sensors

Section titled “Technical Documentation & Analysis: Ultrasensitive Diamond MEMS Magnetic Force Sensors”

Executive Summary

Section titled “Executive Summary”

This research demonstrates the successful integration of a high-quality Single-Crystal Diamond (SCD) MEMS resonator with a permanent magnetic particle (NdFeB) to create an ultra-sensitive and highly reliable magnetic force sensor operating at room temperature.

  • Material Superiority: SCD MPCVD material provides exceptional thermal stability, high Q factor (up to 6400), and robust mechanical properties essential for high-performance MEMS devices.
  • Record Sensitivity: The sensor achieved an ultra-low detectable force of $1.8 \times 10^{-16}$ N/Hz1/2 in the first mode at ambient conditions, surpassing typical silicon resonator performance.
  • Exceptional Stability: Demonstrated ultralow resonant frequency fluctuation, measured at only $7.89 \times 10^{-4}$ Hz at room temperature, ensuring stable and reliable operation.
  • High Magnetic Response: Achieved a high magnetic sensitivity of 0.303%/(mT/mm), leveraging the magnetic field gradient effect for enhanced detection.
  • Advanced Application: Successfully demonstrated 3D magnetic force imaging capability on the SCD platform, enabling visualization of magnetic force distributions.
  • Future Roadmap: The authors project that reducing the SCD resonator thickness below 100 nm (while maintaining high Q) will enable next-generation sensitivity levels approaching $\approx$ aN/Hz1/2.
  • Methodology: Devices were fabricated using MPCVD growth of high-purity SCD epilayers on HTHP substrates via the Ion-Implantation Assisted Lift-off (IAL) technique.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Detectable Force (Fmin)$1.8 \times 10^{-16}$N/Hz1/21st Mode, Room Temperature Operation
Magnetic Sensitivity0.303%/(mT/mm)1st Mode
Resonant Frequency (f0)23.170kHz1st Mode, with NdFeB particle
Quality Factor (Q)6400Dimensionless1st Mode, with NdFeB particle
Frequency Fluctuation ($\Delta$fmin)$7.89 \times 10^{-4}$HzUltralow stability at Room Temperature
Response Time98.8ms1st Mode
Cantilever Thickness (t)700nmSCD Epilayer thickness
Cantilever Width10”mDevice dimension
Target Thickness for aN Sensitivity< 100nmRequired for next-generation performance
MPCVD Growth Temperature840°CStandard process parameter
Ion Implantation Dose$10^{16}$cm-2Carbon ions, 180 keV
Minimum Detectable Force (3D Imaging)5.5pNAchieved during 3D mapping

Key Methodologies

Section titled “Key Methodologies”

The SCD MEMS resonators were fabricated using a specialized process combining high-quality material growth and precise micro-machining techniques:

  1. Substrate Preparation: High-Temperature High-Pressure (HTHP) Type-Ib (100) SCD substrates were used, requiring an RMS surface roughness lower than 1 nm.
  2. Ion Implantation: Carbon ions (180 keV, $10^{16}$ cm-2 dose) were implanted to create a sacrificial layer, which converts to a graphite-like layer ($\approx$ 200 nm) during subsequent growth.
  3. MPCVD Epilayer Growth: Single-Crystal Diamond (SCD) epilayers were deposited using a Microwave Plasma Chemical Vapor Deposition (MPCVD) system to ensure high crystal quality and precise thickness control.
    • Recipe Parameters: Methane concentration 0.5%, Hydrogen flow 500 sccm, Microwave power 1 kW, Working temperature 840 °C.
  4. Patterning and Etching: A 150 nm Aluminum mask was applied, followed by dry etching using Reactive Ion Etching (RIE) with an Inductively Coupled Plasma (ICP) system in a pure oxygen environment.
  5. Post-Fabrication Annealing: Samples were annealed at 1100 °C under ultrahigh vacuum (< $10^{-7}$ Pa) for 3 hours to reduce defects and enhance Q-factors, followed by oxygen etching and a final 650 °C anneal.
  6. Heterogeneous Integration: The free SCD cantilever was transferred to a Si substrate using a non-destructive glass needle method and secured with conductive glue. A 14 ”m diameter NdFeB magnetic particle was attached to the cantilever tip.

6CCVD Solutions & Capabilities

Section titled “6CCVD Solutions & Capabilities”

6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials necessary to replicate, optimize, and scale the SCD MEMS magnetic force sensors described in this research. Our capabilities directly address the material requirements for achieving ultra-high sensitivity and stability.

Applicable Materials

Section titled “Applicable Materials”

To replicate the high Q-factor and thermal stability demonstrated in this work, researchers require the highest quality SCD material.

6CCVD Material SolutionSpecification MatchApplication Relevance
Optical Grade Single Crystal Diamond (SCD)Low defect density, high purity, and low internal stress (as confirmed by low Raman FWHM).Essential for achieving high Q factors (Q > 6000) and minimizing thermal noise in MEMS resonators.
Custom SCD Thin FilmsRequired for the Ion-Implantation Assisted Lift-off (IAL) technique.Enables precise control over the resonator thickness (700 nm used in the paper).
High-Purity SCD SubstratesHTHP Type-Ib (100) substrates with Ra < 1 nm.Provides the necessary foundation for high-quality MPCVD epilayer growth and subsequent IAL processing.

Customization Potential for Next-Generation Devices

Section titled “Customization Potential for Next-Generation Devices”

The research explicitly identifies the need to reduce resonator thickness below 100 nm to achieve $\approx$ aN/Hz1/2 sensitivity. 6CCVD’s MPCVD capabilities are perfectly suited to meet this demanding requirement.

  • Ultra-Thin Film Control: 6CCVD offers SCD epilayer thickness control from 0.1 ”m (100 nm) down to 0.1 ”m (100 nm), enabling the fabrication of the next generation of ultra-thin resonators required for aN-level force detection.
  • Custom Dimensions and Geometry: We provide custom laser cutting and etching services to produce precise cantilever geometries (e.g., 10 ”m width, 120 ”m length) and plates/wafers up to 125 mm (PCD).
  • Advanced Metalization: The integration of magnetic particles often requires specific metal adhesion layers. 6CCVD offers in-house metalization services, including Ti, Pt, Au, Pd, W, and Cu, allowing for optimized bonding and electrical contact layers for complex MEMS integration.
  • Polishing Excellence: Our SCD material is polished to an industry-leading surface roughness of Ra < 1 nm, crucial for minimizing surface friction and maximizing the Q factor in thin-film resonators.

Engineering Support

Section titled “Engineering Support”

6CCVD’s in-house PhD team specializes in the material science and engineering of diamond for advanced applications. We offer consultation services to assist researchers and engineers in optimizing material selection for similar MEMS Magnetic Force Sensing and Magnetic Resonance Force Microscopy (MRFM) projects. We ensure the supplied material meets the stringent quality and dimensional tolerances required for high-yield IAL fabrication processes.

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

View Original Abstract

Abstract Developing magnetic force sensors with a simple structure, high sensitivity, and exceptional reliability at room temperature remains challenging due to frequency fluctuations and noise suppression issues. In this work, an ultra‐sensitive and highly reliable magnetic force sensor is presented by integrating a single‐crystal diamond (SCD) MEMS resonator with a permanent magnetic particle. The magnetic particle serves as the sensing element, enabling precise detection of magnetic field gradients under a field bath. The SCD‐based MEMS sensor exhibits outstanding performance, achieving an ultra‐low detectable force of 1.8 × 10 −16 N/Hz 1/2 , a high magnetic sensitivity of 0.303%/(mT/mm), and a response time of 98.8 ms in the first mode at room temperature. Notably, the resonant frequency fluctuation is remarkably low, reaching 7.89 × 10 −4 Hz at room temperature, ensuring stable and reliable operation. Furthermore, a 3D magnetic force imaging sensor based on the SCD platform, capable of visualizing the 3D distribution of magnetic forces is demonstrated. This work lays a solid foundation for the advancement of SCD MEMS‐based magnetic imaging sensors, offering unparalleled sensitivity, reliability, and tunable spatial resolution for next‐generation magnetic imaging applications.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2012 - in SQUID Sensors: Fundamentals, Fabrication and Applications

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