Precision temperature sensing in the presence of magnetic field noise and vice-versa using nitrogen-vacancy centers in diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2018-07-02 |
| Journal | Applied Physics Letters |
| Authors | Adam M. Wojciechowski, MĂŒrsel Karadas, Christian Osterkamp, Steffen Jankuhn, Jan Meijer |
| Institutions | Center for Integrated Quantum Science and Technology, Ărsted (Denmark) |
| Citations | 52 |
| Analysis | Full AI Review Included |
6CCVD Technical Analysis: Decoupled Quantum Sensing in NV Diamond
Section titled â6CCVD Technical Analysis: Decoupled Quantum Sensing in NV DiamondâResearch Paper: Precision temperature sensing in the presence of magnetic field noise and vice-versa using nitrogen-vacancy centers in diamond (arXiv:1802.07224v1)
Executive Summary
Section titled âExecutive SummaryâThis paper validates a highly robust methodology for decoupling magnetic field ($\Delta B$) and temperature ($\Delta T$) measurements using Nitrogen-Vacancy (NV) centers in MPCVD single crystal diamond (SCD). This advancement is critical for precision quantum sensing where environmental noise typically limits accuracy.
- Core Achievement: Demonstrated decoupled, high-precision sensing of $\Delta B$ and $\Delta T$ by simultaneously driving two distinct NV hyperfine transitions using in-phase (common-mode cancellation) or out-of-phase (differential-mode cancellation) frequency modulation (FM) of microwave (MW) fields.
- Performance Metrics: Achieved high sensitivity of 1.4 nT Hz-1/2 for magnetic fields and 430 ”K Hz-1/2 for temperature, leveraging the common-mode shift dependency on temperature and the differential shift dependency on magnetic field.
- Material Requirement: Requires high-purity, isotopically enriched ([12C] > 99.99%) SCD with precisely controlled 15N doping in a shallow 1 ”m layer to optimize NV concentration and reduce noise.
- High-Bandwidth Measurement: Technique allows for recording temperature transients on millisecond timescales in a single-shot measurement, overcoming limitations of previous averaging protocols.
- Scalability: The method is inherently extendable to wide-field camera-imaging scenarios, which benefits directly from 6CCVDâs large-area polycrystalline diamond (PCD) capabilities.
- Fabrication Complexity: The approach necessitated complex post-processing, including ion implantation (1.8 MeV He+), high-temperature annealing (900 °C), and multi-layer thin-film metalization (SiO2 AR, Al reflective/absorptive coating).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Material Type | Single Crystal Diamond (SCD) | N/A | [100]-oriented, Ultrapure |
| Purity (Background N) | [N] < 1 ppb | N/A | Required for low spin noise/long coherence |
| Isotopic Enrichment | [12C] > 99.99% | % | CVD Overgrown Layer (approx. 1 ”m thick) |
| Dimensions | 2 x 2 x 0.5 | mm3 | Sample Size |
| Doping Isotope | 15N | ppm | Concentration: ~10 ppm in 1 ”m layer |
| Vacancy Creation | 1.8 MeV He Ions | cm-2 | Implantation dose: 1015 cm-2 |
| Annealing Temperature | 900 | °C | 2 hours duration |
| Magnetic Sensitivity | 1.4 nT Hz-1/2 | N/A | Achieved Sensitivity (up to ~1 kHz BW) |
| Temperature Sensitivity | 430 ”K Hz-1/2 | N/A | Achieved Sensitivity (Noise Floor) |
| MW Modulation Frequency | 40 | kHz | Sine-wave modulation |
| MW Frequency Deviation (FM) | ±500 | kHz | Used for ODMR detection |
| Zero-Field Splitting Shift (dT) | ~75 | Hz/mK | Temperature-induced shift (D) |
| Illumination Wavelength | 532 | nm | Green laser excitation (MW coupling) |
| Surface Metalization (Top) | Al (300 nm) | nm | Reflects fluorescence, absorbs heating laser |
| Surface Coating (Bottom) | SiO2 (95 nm) | nm | Anti-Reflection (AR) coating |
Key Methodologies
Section titled âKey MethodologiesâThe experiment relies on meticulous material fabrication and a sophisticated CW-ODMR setup utilizing dual frequency-modulated MW sources for noise cancellation.
Material Synthesis and Preparation
Section titled âMaterial Synthesis and Preparationâ- CVD Growth: An ultrapure [100]-oriented SCD substrate (< 1 ppb N) was used. A thin (approximately 1 ”m) SCD layer was overgrown via CVD, ensuring > 99.99% isotopic purity ([12C]) and doped specifically with 15N (at ~10 ppm concentration).
- Vacancy Introduction: The sample was implanted using 1.8 MeV Helium ions (He+) at a dose of 1015 cm-2 to create NV precursors.
- Activation: Vacancies were activated by annealing the diamond at 900 °C for 2 hours, resulting in an NV concentration of 0.1 - 1 ppm.
- Surface Engineering: The bottom face was coated with 95 nm SiO2 for Anti-Reflection (AR). The top surface received a 300 nm Aluminum (Al) coating, serving both as a reflector for fluorescence collection and an absorber for external heating tests.
Sensing Protocol (Decoupled Detection)
Section titled âSensing Protocol (Decoupled Detection)â- MW Setup: Two independent MW generators (SRS SG394) were combined, amplified, and routed to an in-plane MW antenna structure.
- Modulation: Both MW sources were simultaneously driven using either frequency modulation (FM) or amplitude modulation (AM) at a 40 kHz sine-wave frequency (modulation depth 100% AM or ±500 kHz FM).
- Targeting Transitions: The dual MW fields addressed two distinct, well-resolved hyperfine transitions (ms = 0 â ms = ±1) that shared the ms = 0 sub-state.
- Decoupling:
- Temperature Sensitivity (B-immune): Achieved by driving two distinct electron transitions (e.g., transitions 2 & 4) with the same modulation phase ($\phi_{1} = \phi_{2} = 0$). This configuration causes the magnetic field-dependent terms to cancel out (differential shift opposite for ms = +1 states), leaving only the common-mode shift induced by temperature.
- Magnetic Field Sensitivity (T-immune): Achieved by driving the same pair of transitions (e.g., 2 & 4) with the opposite modulation phase ($\phi_{1} = 0, \phi_{2} = 180^{\circ}$). This cancels the common-mode temperature shift, leaving only the differential shift caused by the magnetic field.
- Readout: Fluorescence signal was collected by a photodetector (Thorlabs DET36A) and phase-sensitively demodulated by a lock-in amplifier (SRS SR850) using a 100 ”s to 1 ms time constant.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the absolute necessity of high-specification, custom-engineered diamond materials to push the boundaries of quantum sensing. 6CCVD is uniquely positioned to supply the materials required to replicate, extend, and scale this decoupled sensing platform.
Applicable Materials
Section titled âApplicable Materialsâ| Research Requirement | 6CCVD Applicable Material | Engineering Rationale & Benefit |
|---|---|---|
| Ultrapure Substrate | Optical Grade Single Crystal Diamond (SCD) | Our SCD features extremely low native nitrogen content, essential for maximizing NV coherence time (T2) and magnetic sensitivity. Available in [100] orientation as used in this study. |
| Isotopic Purification | Isotopically Controlled SCD | We offer CVD growth utilizing specialized gas sources to achieve > 99.99% 12C isotopic purity, crucial for reducing spin bath decoherence and improving T/B sensing performance. |
| Shallow Doping/Layer Thickness | Custom Doped SCD Layer | The study requires a precisely controlled 1 ”m thick layer doped with 15N. 6CCVD offers custom SCD layer thickness control from 0.1 ”m up to 500 ”m, ensuring optimal NV proximity to the surface while maintaining high crystal quality. |
| Specific Dopant Source | Custom Isotope Doping (15N) | We supply CVD diamond using specified isotopic gas sources, enabling the use of 15N as required for the 3.05 MHz hyperfine structure utilized in this dual-frequency scheme. |
| Large-Area Scalability | Inch-size Polycrystalline Diamond (PCD) | For scaling the wide-field sensing scenario mentioned in the paper, 6CCVD offers large-area PCD wafers up to 125 mm, providing a cost-effective platform for industrial or multi-pixel sensor arrays. |
Customization Potential
Section titled âCustomization PotentialâReplicating this advanced research requires tailored post-processing and surface modifications, all available in-house at 6CCVD:
- Metalization Services: The experiment used Aluminum (Al) and Silicon Dioxide (SiO2) coatings. 6CCVD provides comprehensive metalization capabilities including Au, Pt, Pd, Ti, W, and Cu, as well as custom dielectric coatings (like SiO2) for Anti-Reflection (AR) or protective layers, meeting specific optical and electrical requirements.
- Surface Finish: The high sensitivity of NV centers requires exceptional surface quality. 6CCVD guarantees ultra-smooth finishes: Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD, minimizing surface-related noise and optimizing NV creation via implantation/annealing.
- Dimensional Accuracy: Although the paper used small 2 x 2 mm samples, 6CCVD offers high-precision laser cutting and shaping services to produce custom dimensions, thicknesses (SCD/PCD up to 500 ”m), and substrate dimensions (up to 10 mm thick).
Engineering Support
Section titled âEngineering SupportâThis decoupled sensing scheme relies on precise material engineering, including isotopic concentration control, optimal NV depth via implantation/annealing, and surface coating integration. 6CCVDâs in-house PhD team provides expert consultation on:
- Material Selection: Guiding customers through the trade-offs between SCD (highest coherence) and PCD (largest area/lowest cost) for specific temperature and magnetic field sensing projects.
- Fabrication Recipe Optimization: Assisting in defining precise doping concentration and layer thickness for desired NV densities and spin properties ($T_{1}, T_{2}$).
- Integration Support: Consulting on optimal metal stack architectures and polishing levels necessary for integrating diamond sensing platforms into complex optical/electrical setups.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
We demonstrate a technique for precision sensing of the temperature or the magnetic field by simultaneously driving two hyperfine transitions involving distinct electronic states of the nitrogen-vacancy center in diamond. Frequency modulation of both driving fields is used with either the same or opposite phase, resulting in the immunity to fluctuations in either the magnetic field or the temperature, respectively. In this way, a sensitivity of 1.4 nT Hzâ1â2 or 430 ÎŒK Hzâ1â2 is demonstrated. The presented technique only requires a single frequency demodulator and enables the use of phase-sensitive camera imaging sensors. A simple extension of the method utilizing two demodulators allows for simultaneous, independent, and high-bandwidth monitoring of both the magnetic field and the temperature.