Electron spin resonance spectroscopy of small ensemble paramagnetic spins using a single nitrogen-vacancy center in diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2016-09-28 |
| Journal | Journal of Applied Physics |
| Authors | Chathuranga Abeywardana, Viktor Stepanov, Franklin H. Cho, Susumu Takahashi |
| Institutions | University of Southern California |
| Citations | 22 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Nanoscale Spin Sensing in Diamond
Section titled âTechnical Documentation & Analysis: Nanoscale Spin Sensing in DiamondâExecutive Summary
Section titled âExecutive SummaryâThis research demonstrates the successful application of a single Nitrogen-Vacancy (NV) center in diamond as an ultra-sensitive probe for Electron Spin Resonance (ESR) spectroscopy, focusing on the surrounding nanoscale spin bath.
- Core Achievement: Identification and characterization of the static and dynamic properties of substitutional single nitrogen impurity spins (P1 centers) surrounding an isolated NV center.
- Methodology: Utilized advanced pulsed techniques including Rabi oscillations, Free-Induction Decay (FID), Spin Echo (SE), and Double Electron-Electron Resonance (DEER) spectroscopy.
- Material Requirement: The experiment relied on a Type-Ib diamond crystal with a controlled, moderate nitrogen concentration (10-100 ppm) to facilitate the spin bath coupling.
- Sensitivity Demonstrated: The NV probe detected an effective magnetic dipolar field of $\sim 6$ ”T, equivalent to a single spin at a distance of $\sim 7$ nm.
- Quantification: Through simulation, the number of detected bath spins contributing to the NV-based ESR signal was estimated to be $\le 50$ spins.
- Implication for 6CCVD: This work validates the critical need for high-quality, MPCVD-grown diamond with precise control over nitrogen concentration and crystal purity for next-generation quantum sensing and magnetic resonance applications.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results and material characterization:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Type Used | Type-Ib (HPHT) | N/A | Commercially available crystal used for bulk and single NV measurements. |
| Nitrogen (P1) Concentration | 10 to 100 | ppm | Bulk concentration corresponding to 4 x 1015 to 4 x 1016 spins/cmÂł. |
| Local N Concentration (NV 1) | 20 | ppm | Estimated local concentration of bath spins around NV 1. |
| Bulk ESR Frequency | 230 | GHz | Used for ensemble characterization of P1 centers. |
| Single NV ODMR Frequency | 1.868 | GHz | Corresponds to the ms = 0 $\leftrightarrow$ -1 transition at B0. |
| External Magnetic Field (B0) | 35.7 | mT | Applied along the <111> axis for ODMR/DEER measurements. |
| Detected Dipolar Field (Bdip,eff) | $\sim 6$ | ”T | Measured via DEER, equivalent to a single spin at $\sim 7$ nm. |
| NV Spin Decoherence Time (T2) | 1.2 to 3.4 | ”s | Measured across four different NV centers (NV 1-4). |
| Rabi Oscillation Frequency (fRabi) | 7.4 $\pm$ 0.2 | MHz | Measured for NV 1. |
| $\pi$/2 Pulse Length | 34 | ns | Determined from Rabi oscillations for NV 1. |
| Estimated Detected Spins | $\le 50$ | Spins | Estimated via simulation of NV-based ESR intensity. |
Key Methodologies
Section titled âKey MethodologiesâThe experiment combined bulk characterization with highly localized quantum sensing techniques to analyze the spin environment.
- Sample Characterization: Ensemble continuous-wave (cw) ESR spectroscopy was performed at 230 GHz on the Type-Ib diamond crystal at room temperature to confirm the substitutional single nitrogen center (P1 center) as the dominant paramagnetic impurity.
- Single NV Identification: Isolated NV centers were located using a home-built confocal microscope system, confirmed via Fluorescence (FL) autocorrelation (revealing a dip at zero delay) and cw Optically Detected Magnetic Resonance (ODMR).
- Spin State Manipulation: Pulsed ODMR measurements were performed using a 2 ”s initialization laser pulse, microwave pulse sequences (delivered via a 20 ”m gold wire), and a 300 ns read-out laser pulse.
- Spin Bath Dynamics: Rabi oscillation, Free-Induction Decay (FID), and Spin Echo (SE) measurements were conducted at B0 = 35.7 mT and 1.868 GHz to extract the spin-bath coupling constant ($b$) and the spin flip-flop rate ($1/\tau_{C}$).
- NV-based ESR (DEER): Double Electron-Electron Resonance (DEER) spectroscopy was employed, using the NV center as the probe spin and an additional $\pi$-pulse (MW2) to flip the surrounding P1 bath spins, causing a phase shift in the NV echo signal.
- Spin Quantification: A computational simulation was used to model the effective magnetic dipole field (Bdip,eff) generated by the surrounding N spins, allowing the researchers to estimate the number of detected spins contributing to the observed DEER signal intensity ($\le 50$).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe success of this nanoscale magnetic sensing research hinges on the quality and precise impurity control of the diamond substrate. 6CCVDâs expertise in MPCVD growth and post-processing services directly addresses the material requirements necessary to replicate, optimize, and scale this quantum technology.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the long coherence times (T2) and controlled spin bath coupling required for advanced NV-based sensing, 6CCVD recommends the following materials, superior to the HPHT Type-Ib crystal used in the study:
| 6CCVD Material | Description & Application | Advantage over Type-Ib |
|---|---|---|
| Optical Grade SCD (Type-IIa) | Ultra-high purity single crystal diamond wafers (SCD) with extremely low native nitrogen content (< 1 ppb). | Provides the longest possible T2 coherence times, essential for high-sensitivity quantum measurements. NV centers are created via controlled implantation/annealing post-growth. |
| Controlled Nitrogen-Doped SCD | Single Crystal Diamond grown with precise, in-situ nitrogen doping (MPCVD). | Allows direct control over the P1 center concentration (e.g., 1 ppm to 100 ppm) to optimize the spin bath density and NV-P1 coupling, crucial for DEER experiments. |
| Heavy Boron Doped PCD (BDD) | Polycrystalline diamond wafers with high boron doping. | While not suitable for single NV sensing, BDD is ideal for electrochemical and high-power electronic applications requiring high conductivity and robust diamond properties. |
Customization Potential
Section titled âCustomization Potentialâ6CCVD provides the necessary engineering capabilities to move this research from small, bulk crystals to integrated, scalable quantum devices.
- Custom Dimensions: While the paper used a 1.5 x 1.5 mmÂł sample, 6CCVD offers SCD plates up to 10x10 mm and PCD wafers up to 125mm in diameter, facilitating the development of large-scale sensor arrays.
- Precision Polishing: The experiment requires high-fidelity optical readout. 6CCVD guarantees Ra < 1 nm polishing on SCD, minimizing scattering losses and maximizing photon collection efficiency for single NV detection.
- Integrated Metalization: The experiment used an external gold wire for microwave delivery. 6CCVD offers in-house metalization services (Au, Pt, Ti, W, Cu) to deposit custom microwave striplines or coplanar waveguides directly onto the diamond surface, improving coupling efficiency and device integration.
- Thickness Control: We provide precise thickness control for SCD and PCD layers from 0.1 ”m up to 500 ”m, allowing researchers to optimize the proximity of the NV layer to the surface for enhanced nanoscale sensing.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in the material science of quantum defects. We can assist researchers with similar nanoscale magnetic sensing projects by:
- Optimizing Nitrogen Doping: Consulting on the ideal P1 concentration and depth profile required to balance long T2 coherence with sufficient spin bath coupling for DEER measurements.
- Substrate Selection: Guiding the choice between high-purity SCD for implanted NVs or in-situ doped SCD for specific bulk NV applications.
- Device Integration: Designing custom metalization patterns and dimensions for efficient microwave and optical coupling.
- Global Logistics: Ensuring reliable global shipping (DDU default, DDP available) of sensitive diamond materials.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
A nitrogen-vacancy (NV) center in diamond is a promising sensor for nanoscale magnetic sensing. Here, we report on electron spin resonance (ESR) spectroscopy using a single NV center in diamond. First, using a 230 GHz ESR spectrometer, we performed ensemble ESR of a type-Ib sample crystal and identified a substitutional single nitrogen impurity as a major paramagnetic center in the sample crystal. Then, we carried out free-induction decay and spin echo measurements of the single NV center to study static and dynamic properties of nanoscale bath spins surrounding the NV center. We also measured ESR spectrum of the bath spins using double electron-electron resonance spectroscopy with the single NV center. The spectrum analysis of the NV-based ESR measurement identified that the detected spins are the nitrogen impurity spins. The experiment was also performed with several other single NV centers in the diamond sample and demonstrated that the properties of the bath spins are unique to the NV centers indicating the probe of spins in the microscopic volume using NV-based ESR. Finally, we discussed the number of spins detected by the NV-based ESR spectroscopy. By comparing the experimental result with simulation, we estimated the number of the detected spins to be â€50 spins.