Readout and control of an endofullerene electronic spin
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-12-17 |
| Journal | Nature Communications |
| Authors | Dinesh Pinto, Domenico Paone, Bastian Kern, Tim Dierker, René Wieczorek |
| Institutions | University of Stuttgart, Ăcole Polytechnique FĂ©dĂ©rale de Lausanne |
| Citations | 32 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: MPCVD Diamond for Endofullerene Quantum Spintronics
Section titled âTechnical Documentation & Analysis: MPCVD Diamond for Endofullerene Quantum SpintronicsâThis document analyzes the research paper âReadout and control of an endofullerene electronic spinâ to highlight the critical role of high-purity MPCVD diamond substrates and to position 6CCVDâs capabilities as the ideal solution for replicating and advancing this quantum spintronics research.
Executive Summary
Section titled âExecutive SummaryâThe research successfully demonstrates single-spin readout and control of encapsulated nitrogen endofullerenes ($^{14}$N@C$_{60}$) using a near-surface Nitrogen Vacancy (NV) center in diamond. This work is foundational for scalable quantum technologies.
- Core Achievement: First demonstration of single-spin EPR readout and RF pulse control (Rabi oscillations, spin-echo) of an endofullerene electronic spin.
- Sensing Mechanism: Utilizes a single near-surface NV center in electronic-grade CVD diamond as a nanoscale magnetic sensor operating at 4.7 K.
- Critical Material Requirement: The experiment relies on ultra-low defect density Single Crystal Diamond (SCD) to achieve the long NV coherence times (T$_{2}$) necessary for robust quantum control.
- Key Interaction: Exploitation of the strong magnetic dipolar interaction between the NV center and the surface-adsorbed $^{14}$N@C$_{60}$ spin.
- Surface Effects: Modeling confirms that surface adsorption on the diamond enhances the isotropic hyperfine constant (19 MHz) and zero-field splitting (1.52 MHz).
- Future Scaling: The results pave the way for building large-scale endofullerene quantum machines and integrating nuclear quantum memories, requiring high-quality, scalable diamond substrates.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results, demonstrating the stringent requirements for the diamond substrate and operational environment.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Operating Temperature | 4.7 | K | Single-spin EPR measurements |
| Diamond Substrate Thickness | 30 | ”m | Electronic grade [100] CVD diamond |
| Nitrogen Implantation Energy | 5 | keV | Used to create near-surface NV centers |
| Static Magnetic Field (B0) | 9.697 | mT | Applied field for EPR spectrum |
| NV-N@C$_{60}$ Separation (r) | $\approx$5.6(1) | nm | Calculated from initial linear dephasing |
| NV-N@C$_{60}$ Coupling Strength (J) | 20.29(2) | MHz | Dipolar coupling strength |
| N@C$_{60}$ Rabi Frequency (VR) | Up to 12.47(1) | MHz | Tunable spin-state switching rate |
| N@C${60}$ Coherence Time (T${2}$) | $\ge$ 1 | ”s | Lower limit measured via spin-echo |
| Enhanced Hyperfine Constant (a) | 19 | MHz | Due to surface adsorption effects |
| Axial Zero-Field Splitting (D) | 1.52 | MHz | Due to surface adsorption effects |
Key Methodologies
Section titled âKey MethodologiesâThe experiment required precise control over diamond material properties, surface preparation, and nanostructuring to ensure optimal NV center performance and coupling efficiency.
- Substrate Selection: Used 30 ”m thick electronic grade [100] CVD diamond plate.
- NV Center Creation: Implanted with $^{15}$N at 5 keV (to ensure near-surface location), followed by annealing at 975 °C for 2 hours.
- Optical Enhancement: Nanopillar waveguides (700 nm base, 400 nm tip, 1 ”m height) were etched into the diamond surface to increase optical collection efficiency.
- Surface Cleaning and Termination: The diamond surface was cleaned and oxygen terminated by boiling in a tri-acid mixture (HNO3:H2SO4:HClO4, 1:1:1) at 200 °C for 5 hours.
- Endofullerene Deposition: A toluene solution of $^{14}$N@C$_{60}$ (0.1 ”L L-1 concentration) was drop-coated onto the oxygen-terminated diamond surface under ambient conditions.
- Measurement: Single-spin EPR performed using pulsed electron-electron double resonance (DEER) spectroscopy in a home-built low-temperature (4.7 K) and ultra-high vacuum (10-10 mbar) setup.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe success of this quantum spintronics experiment hinges on the quality and precise engineering of the diamond substrate. 6CCVD specializes in providing the high-purity, custom-engineered MPCVD diamond required to replicate and scale this research.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the long coherence times (T$_{2}$) and low magnetic noise necessary for single-spin control, the researchers require the highest quality diamond.
| Research Requirement | 6CCVD Material Recommendation | Technical Rationale |
|---|---|---|
| Electronic Grade, Low Defect Density | Optical Grade Single Crystal Diamond (SCD) | Our SCD material is grown via MPCVD with ultra-low nitrogen incorporation, minimizing background spin baths and maximizing NV T$_{2}$ coherence times, essential for quantum memory applications. |
| Surface Sensing/Adsorption | Shallow NV Optimized SCD | We provide SCD substrates optimized for shallow implantation (like the 5 keV used here), ensuring NV centers are close to the surface while maintaining bulk-like coherence properties. |
| High-Throughput Scaling | Inch-Size SCD and Large-Area PCD | For future large-scale endofullerene quantum machines, 6CCVD offers SCD wafers up to 125mm (PCD) and large-area SCD, enabling high-volume device fabrication. |
Customization Potential
Section titled âCustomization Potentialâ6CCVDâs in-house engineering and fabrication capabilities directly address the specific physical requirements detailed in the paper:
| Paper Requirement | 6CCVD Customization Service | Specification Match |
|---|---|---|
| Precise Thickness Control | Custom SCD Thickness | We offer SCD plates from 0.1 ”m up to 500 ”m, allowing researchers to precisely match the 30 ”m thickness used or optimize for future designs. |
| Ultra-Smooth Surface | High-Precision Polishing | Our standard SCD polishing achieves surface roughness Ra < 1 nm. This atomic-scale smoothness is critical for minimizing surface magnetic noise and ensuring stable endofullerene adsorption. |
| Nanostructure Preparation | Custom Laser Cutting & Shaping | While the paper used RIE etching for nanopillars, 6CCVD can provide substrates pre-cut to complex geometries or specific dimensions (up to 125mm) ready for subsequent nanofabrication. |
| Interface Engineering | Custom Metalization Services | Although the paper did not use metalization on the NV area, 6CCVD offers internal capabilities for depositing Au, Pt, Pd, Ti, W, and Cu contacts, crucial for integrating RF/MW delivery lines directly onto the diamond surface for pulsed control. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team provides expert consultation on material selection, surface preparation, and integration challenges for advanced quantum applications. We can assist researchers in optimizing diamond properties for similar Quantum Sensing and Spintronics projects, including selecting the appropriate crystal orientation ([100] vs. [111]) and managing surface termination effects that influence hyperfine interactions.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.