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6CCVD Research

Nanoscale Imaging of Current Density with a Single-Spin Magnetometer

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2017-03-24
JournalNano Letters
AuthorsKai Chang, Alexander Eichler, J. Rhensius, Leandro Lorenzelli, Christian L. Degen
InstitutionsETH Zurich
Citations104
AnalysisFull AI Review Included

Technical Documentation & Prospectus: Nanoscale Current Density Imaging via Diamond Magnetometry

Section titled “Technical Documentation & Prospectus: Nanoscale Current Density Imaging via Diamond Magnetometry”

Executive Summary

Section titled “Executive Summary”
  • Application Focus: Demonstrates non-invasive, two-dimensional current density imaging in nanoscale conductors (Pt nanowires, Carbon Nanotubes) using a scanning diamond nitrogen-vacancy (NV) center magnetometer.
  • Performance: Achieves exceptional spatial resolution of 22 nm (best effort) at room temperature, enabling the visualization of fine current dynamics in 2D material networks.
  • Sensitivity: Detects DC currents down to approximately 1 ”A above a baseline current density of 2·104 A/cm2, with projected future sensitivity nearing 1 nA using pulsed methods.
  • Methodology: Utilizes Continuous-Wave Electron Paramagnetic Resonance (CW-EPR) combined with a differential measurement scheme (±I current modulation) to isolate the Oersted magnetic field generated by the charge flow.
  • Relevance to 6CCVD: Future research requires high-purity, low-strain Single Crystal Diamond (SCD) for fabricating etched probes capable of achieving sub-10 nm resolution, a core material specialty of 6CCVD.
  • Industrial Impact: This technique offers a critical tool for analyzing electronic transport, conductance variations, and localized phenomena (e.g., branched electron flow, impurity back-scattering) in mesoscopic physics and novel quantum devices.

Technical Specifications

Section titled “Technical Specifications”

The following table extracts key performance metrics and operational parameters relevant to the NV diamond magnetometry technique.

ParameterValueUnitContext
Spatial Resolution (Best Effort)22nmDemonstrated via line cut analysis across Pt nanowire
Spatial Resolution (Typical)50nmStandard reconstructed image resolution
DC Current Sensitivity (Minimum Detectable)~1”AAchieved with CW-EPR technique
Baseline Current Density Sensitivity~2·104A/cm2Root-mean-square noise floor
Projected Current Sensitivity (Pulsed EPR)~1nATarget for future systems using optimized phase-estimation
Target Spatial Resolution (Etched SCD Tips)< 10nmFuture objective utilizing single-crystal diamond probes
NV Tip Standoff Distance (z)25 - 100nmRange used over current-carrying nanowires
Nanowire Dimensions (Cross-Section)50×50 to 100×100nm2Platinum (Pt) test structures
Current Modulation Frequency1kHzUsed for differential measurement to eliminate drift
Operating ConditionsAmbientN/AExperiments conducted at room temperature

Key Methodologies

Section titled “Key Methodologies”

The experiment successfully mapped two-dimensional current density by combining advanced diamond probe technology with sophisticated magnetic field reconstruction techniques.

  1. Sensor Fabrication: Scanning probes were prepared by attaching ~25 nm diameter nanodiamond particles containing a single NV center to the apex of a commercial AFM cantilever.
  2. Sample Preparation: Nanowire test structures (straight sections, turns, Y-shaped junctions) were fabricated using e-beam lithography and Platinum (Pt) deposition. Carbon Nanotubes (CNTs) were grown vertically and contacted using e-beam lithography.
  3. Magnetic Field Sensing (CW-EPR): The NV spin resonance frequency was continuously monitored via optical fluorescence detection and microwave irradiation. The local DC magnetic field (Oersted field) causes a Zeeman shift in the Electron Paramagnetic Resonance (EPR) frequency.
  4. Differential Measurement: To eliminate low-frequency drift and background fields, two EPR spectra were recorded at each point using positive (+I) and negative (-I) DC source current, modulated at 1 kHz.
  5. Standoff Calibration: The NV-to-sample standoff distance (z) was accurately calibrated (typically 25 nm to 100 nm) by fitting one-dimensional line scans across a straight, current-carrying nanowire to an analytical Oersted field model.
  6. Current Density Reconstruction: The 2D current density J(x, y) was mathematically reconstructed from the recorded magnetic field image B||(x, y) using an inverse filtering technique based on an inversion of the Biot-Savart law in Fourier space, employing a Hanning window for spatial filtering.

6CCVD Solutions & Capabilities

Section titled “6CCVD Solutions & Capabilities”

6CCVD provides the specialized MPCVD diamond materials necessary to replicate, optimize, and scale the NV-based current density imaging technology demonstrated in this research. Our capabilities directly address the material and fabrication requirements for next-generation quantum sensing probes.

Applicable Materials & Requirements6CCVD Solution & CapabilityCustomization Potential & Sales Driver
High-Purity Diamond for NV Probes (Required for etched single-crystal tips, target < 10 nm resolution, stable NV coherence)Optical Grade Single Crystal Diamond (SCD): We supply low-strain, high-purity MPCVD SCD required for manufacturing high-performance NV sensors. This material is essential for achieving the projected sub-10 nm spatial resolution and necessary spin coherence times (T1).Custom Substrate Thicknesses: SCD plates are available from 0.1 ”m to 500 ”m thick, allowing researchers to select optimal material for subsequent etching, polishing, and nanotip fabrication processes.
Advanced Polishing for Minimal Standoff (Resolution is critically dependent on NV-to-sample distance z < 100 nm)Ultra-Smooth Polishing Services: 6CCVD guarantees an industry-leading surface finish for SCD substrates, achieving roughness values of Ra < 1 nm. This precision polishing minimizes the standoff distance (z), maximizing measurement fidelity and resolution.Inch-Size PCD Polishing: For large-area metrology stages utilizing Polycrystalline Diamond (PCD) cooling or structural components, we provide PCD wafers up to 125 mm with Ra < 5 nm polishing.
Integrated Test Structures & Conductors (Paper used Pt nanowires for calibration and testing)Internal Metalization Services: We offer custom metal contacts directly on diamond substrates. Our internal capabilities include deposition of Ti, Pt, Au, Pd, W, and Cu, allowing researchers to easily fabricate reference structures, on-chip microwave antennas, or current injection lines critical for NV magnetometry calibration.Custom Device Integration: We provide laser cutting and patterning services to create complex geometries or specific alignment features required for integrating the diamond sensor element into high-precision scanning apparatus.
Highly Conductive Diamond Layers (Potential for integrated on-chip wiring or reference planes)Boron-Doped Diamond (BDD): Available as conductive thin films or thick substrates, BDD can be used to create highly stable, inert electrodes or integrated transmission lines directly beneath the sensing layer for localized microwave control.Global Supply Chain: 6CCVD ensures global shipping (DDU standard, DDP available) of high-specification diamond materials, supporting international research efforts in quantum sensing.

Engineering Support & Call to Action

Section titled “Engineering Support & Call to Action”

6CCVD’s in-house team of PhD material scientists specializes in optimizing MPCVD diamond parameters—including impurity levels, nitrogen concentration, and crystal orientation—specifically for quantum sensing and metrology applications. We can assist with material selection for similar Scanning Diamond Magnetometry projects aiming to push resolution and sensitivity past current limits.

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

View Original Abstract

Charge transport in nanostructures and thin films is fundamental to many phenomena and processes in science and technology, ranging from quantum effects and electronic correlations in mesoscopic physics, to integrated charge- or spin-based electronic circuits, to photoactive layers in energy research. Direct visualization of the charge flow in such structures is challenging due to their nanometer size and the itinerant nature of currents. In this work, we demonstrate noninvasive magnetic imaging of current density in two-dimensional conductor networks including metallic nanowires and carbon nanotubes. Our sensor is the electronic spin of a diamond nitrogen-vacancy center attached to a scanning tip and operated under ambient conditions. Using a differential measurement technique, we detect DC currents down to a few ÎŒA with a current density noise floor of ∌2 × 10<sup>4</sup> A/cm<sup>2</sup>. Reconstructed images have a spatial resolution of typically 50 nm, with a best-effort value of 22 nm. Current density imaging offers a new route for studying electronic transport and conductance variations in two-dimensional materials and devices, with many exciting applications in condensed matter physics and materials science.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 1975 - Classical electrodynamics

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