Scanning Nanospin Ensemble Microscope for Nanoscale Magnetic and Thermal Imaging
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-12-28 |
| Journal | Nano Letters |
| Authors | JeanâPhilippe Tetienne, Alain H. Lombard, David Simpson, Cameron Ritchie, Jianing Lu |
| Institutions | Centre for Quantum Computation and Communication Technology, Ăcole Normale SupĂ©rieure Paris-Saclay |
| Citations | 94 |
| Analysis | Full AI Review Included |
6CCVD Technical Analysis & Quantum Sensing Solutions
Section titled â6CCVD Technical Analysis & Quantum Sensing SolutionsâResearch Paper: Scanning Nano-spin Ensemble Microscope for Nanoscale Magnetic and Thermal Imaging (arXiv:1509.00586v2)
Executive Summary
Section titled âExecutive SummaryâThis paper successfully demonstrates a highly practical scanning quantum probe microscope (QSPM) leveraging Nitrogen-Vacancy (NV) spin ensembles within nanodiamonds attached to an Atomic Force Microscope (AFM) tip. This approach addresses critical limitationsânamely, long acquisition times and lack of simultaneous topographyâpresent in prior single NV center QSPM systems.
Key achievements validated in this research include:
- Acquisition Speed Enhancement: Utilizing an NV ensemble ($N \approx 100$ centers) yields a $\sqrt{N} \approx 10$ gain in signal-to-noise ratio, reducing typical imaging acquisition times from tens of hours to approximately one hour.
- Sub-100 nm Spatial Resolution: The instrument demonstrates a lateral spatial resolution down to 60 nm (Full Width at Half Maximum, FWHM), limited by the nanodiamond probe size (~100 nm).
- Dual-Mode Sensing (Magnetic & Thermal): The system successfully images both static magnetic fields ($B_{0}$) and fast magnetic fluctuations ($T_{1}$) generated by maghemite nanoparticles, revealing both ferromagnetic and superparamagnetic components.
- Nanoscale Thermometry in Fluid: Demonstrated thermal imaging capability by mapping photo-induced heating (up to 40 K temperature increase) from a single gold nanoparticle while immersed in water, critical for biological and microelectronic applications.
- NV Material Validation: Confirms the viability of high-NV density Type-Ib nanodiamonds for developing versatile quantum sensing tools suitable for complex environments (e.g., biological samples in fluid).
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the nanodiamond probe characterization and experimental results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Probe Material | Type-Ib Nanodiamonds (rFND-100) | - | Source material, 100 nm diameter. |
| NV Density | $N \approx 100$ | NV centers/particle | Used for $\sqrt{N} \approx 10$ signal gain. |
| Lateral Spatial Resolution | 60 | nm (FWHM) | Measured feature size in spin relaxation image. |
| Total Imaging Time | 60 to 150 | minutes | Typical frame acquisition time for magnetic images. |
| Spin Coherence Time (T2) | $777 \pm 32$ to $898 \pm 96$ | ns | Measured in nanodiamond probes (ND1/ND2). |
| Spin Relaxation Time (T1) | $40 - 400$ | ”s | Typical range in nanodiamonds. |
| Minimum T1 (on sample) | $6.5 \pm 0.6$ | ”s | Measured over largest maghemite aggregate. |
| Static Magnetic Field (Max) | $2.4 \pm 0.2$ | mT | Amplitude $B_{0}$ inferred from aggregates. |
| Fluctuating Field RMS (Max) | $\approx 270$ | ”T-rms | Inferred from $T_{1}$ measurements over aggregates. |
| NV Zero-Field Splitting (ND1) | $D = 2868.9 \pm 0.1$ | MHz | Mean ensemble characteristic. |
| Temperature Increase (Max) | $\approx 40$ | K | Measured $\Delta T$ above heated gold nanoparticle. |
| Laser Excitation Wavelength | 532 | nm | Used for NV excitation and gold particle heating. |
| Laser Power (Thermal Imaging) | $\approx 250$ | ”W | Used for continuous excitation/heating. |
| NV Temperature Sensitivity | $-75$ | kHz/K | Linear conversion factor based on $D$ parameter shift. |
Key Methodologies
Section titled âKey MethodologiesâThe scanning nano-spin ensemble microscope operates based on the integration of diamond quantum sensing technology with conventional AFM techniques.
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Probe Preparation (Nanodiamond Grafting):
- Material: Type-Ib nanodiamonds (~100 nm diameter, high NV concentration) were selected.
- Grafting: Nanodiamonds were mechanically attached (grafted) to the apex or sidewall of a silicon AFM cantilever tip (9 nm nominal radius or 2 ”m plateau tip) by repeated low-speed scanning in AC (tapping) or contact mode.
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Experimental Setup (ODMR-AFM Integration):
- Microscope: Custom-mounted AFM (Asylum Research MFP-3D-BIO) on an inverted optical microscope (Olympus IX-71).
- Optical Excitation: 532 nm laser focused through a high-NA (1.42) objective lens placed below the thin transparent substrate.
- Microwave (MW) Delivery: A custom-fabricated microwave antenna (fabricated by optical lithography and metal deposition) sits on the substrate near the sample to drive the NV spin resonances.
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Quantum Sensing Techniques:
- Optically Detected Magnetic Resonance (ODMR): Fluorescence intensity is monitored while sweeping the MW frequency (2.8 GHz range) to obtain spin resonance spectra, sensitive to static fields ($B$, $E$) and temperature ($T$).
- Spin Resonance Shift Imaging (Static Fields): Two MW frequencies ($\nu_{1}$, $\nu_{2}$) are applied consecutively, and the normalized difference in fluorescence $D(\nu_{1}, \nu_{2})$ maps the static magnetic field $B_{0}$ (Zeeman shift) or temperature $\Delta T$ (crystal field shift).
- Spin Relaxometry (Fast Dynamics): Applying a sequence of laser pulses and measuring the spin relaxation time ($T_{1}$), which is sensitive to magnetic field fluctuations in the $\approx 3$ GHz range (superparamagnetic dynamics).
- Spin Decoherence (Slow Dynamics): Application of MW spin echo sequence measures the coherence time ($T_{2}$), sensitive to field fluctuations in the kHz-MHz range.
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Thermal Imaging Modality:
- Sample Environment: Gold nanoparticle sample and nanodiamond probe immersed in water to ensure quasi-isotropic heat transfer.
- Heating Source: The 532 nm NV excitation laser is absorbed efficiently by the gold particle (due to surface plasmon resonance at ~530 nm), generating localized heat.
- Temperature Mapping: Full spin resonance spectra are recorded at each pixel. The temperature increase $\Delta T$ is inferred directly from the measured change in the NV zero-field splitting parameter $D$ using the known sensitivity factor (-75 kHz/K).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the critical need for advanced, high-quality diamond materials and precise microfabrication techniques to realize next-generation quantum sensors. 6CCVD is uniquely positioned to supply the foundational materials and custom engineering services required to replicate and extend this work into industrial and commercial applications.
Applicable Materials for Quantum Sensing
Section titled âApplicable Materials for Quantum SensingâThe research utilized high-NV density nanodiamonds. 6CCVD offers superior control over NV incorporation and material properties, enabling engineers to transition from nanodiamond powder to robust, scalable substrates.
| Requirement/Application | 6CCVD Material Solution | Why 6CCVD? |
|---|---|---|
| High-Performance QSPM Probes | SCD Substrates (Ultra-low Defect) | Provides the lowest possible background noise and longest intrinsic $T_{1}$ and $T_{2}$ times, crucial for maximizing sensitivity. Can be post-processed for controlled, shallow NV layers. |
| High-Density, Scalable Platforms | SCD/PCD Wafers (Up to 125mm) | Enables wafer-scale fabrication of integrated quantum devices, including on-chip MW antennas and fluidic channels, moving beyond fragile AFM tips. |
| Integrated Bulk Sensing | SCD Substrates (Controlled NV Incorporation) | For applications requiring near-surface NV centers in bulk diamond (an alternative QSPM strategy), we deliver precise NV concentrations and depths (SCD thickness 0.1”m - 500”m). |
| High-Precision Thermometry | Optical Grade SCD (Polished Ra < 1nm) | Ensures minimal light scattering and high thermal conductivity for reliable temperature mapping and heat dissipation studies in microelectronics (as referenced in the paper). |
Customization Potential
Section titled âCustomization PotentialâThe experimental success relied heavily on custom MW antenna fabrication and precise material handling. 6CCVD offers end-to-end services to meet these specific engineering demands:
- Custom Dimensions and Geometries: We provide custom laser cutting and shaping services, enabling the creation of intricate diamond structures, pillars, or tips for QSPM integration. We supply wafers up to 125 mm (PCD) and substrates up to 10 mm thick.
- Integrated Metalization Services: The experiment required sophisticated microwave circuits on the substrate. 6CCVD offers in-house metalization (Au, Pt, Pd, Ti, W, Cu) applied directly to diamond plates, allowing seamless integration of MW antennas, signal lines, and electrodes onto diamond platforms for advanced quantum control.
- Ultra-Smooth Surfaces: Achieving the required spatial resolution necessitates excellent material interaction. Our polishing services achieve surface roughness down to $\text{Ra} < 1\text{nm}$ (SCD) and $\text{Ra} < 5\text{nm}$ (Inch-size PCD), minimizing probe-sample distance variability and optical losses.
Engineering Support
Section titled âEngineering SupportâThe applications demonstratedâincluding imaging fast magnetic dynamics (superparamagnetism) and nanoscale thermal transfer in fluidic and microelectronic environmentsâare highly specialized. 6CCVDâs in-house PhD engineering team possesses deep expertise in diamond material physics and NV-center applications.
We offer comprehensive consulting services to assist customers in selecting optimal material grade, NV engineering parameters (concentration, depth), and suitable metalization schemes for similar projects in:
- Bio-Sensing and Relaxometry: Characterizing spin labels and ion channels in cell membranes.
- Nanoscale Thermal Management: Studying heat transfer and thermal gradients in operating microelectronic devices (a critical bottleneck for future miniaturization).
- Fundamental Physics: Investigating complex magnetic dynamics and exotic quantum systems.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Quantum sensors based on solid-state spins provide tremendous opportunities in a wide range of fields from basic physics and chemistry to biomedical imaging. However, integrating them into a scanning probe microscope to enable practical, nanoscale quantum imaging is a highly challenging task. Recently, the use of single spins in diamond in conjunction with atomic force microscopy techniques has allowed significant progress toward this goal, but generalization of this approach has so far been impeded by long acquisition times or by the absence of simultaneous topographic information. Here, we report on a scanning quantum probe microscope which solves both issues by employing a nanospin ensemble hosted in a nanodiamond. This approach provides up to an order of magnitude gain in acquisition time while preserving sub-100 nm spatial resolution both for the quantum sensor and topographic images. We demonstrate two applications of this microscope. We first image nanoscale clusters of maghemite particles through both spin resonance spectroscopy and spin relaxometry, under ambient conditions. Our images reveal fast magnetic field fluctuations in addition to a static component, indicating the presence of both superparamagnetic and ferromagnetic particles. We next demonstrate a new imaging modality where the nanospin ensemble is used as a thermometer. We use this technique to map the photoinduced heating generated by laser irradiation of a single gold nanoparticle in a fluid environment. This work paves the way toward new applications of quantum probe microscopy such as thermal/magnetic imaging of operating microelectronic devices and magnetic detection of ion channels in cell membranes.