Voltage detected single spin dynamics in diamond at ambient conditions
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-04-14 |
| Journal | Nature Communications |
| Authors | Sergei Trofimov, K. Lips, Boris Naydenov |
| Institutions | Freie UniversitÀt Berlin, University of Utah |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation: Voltage Detected Single Spin Dynamics (SVDMR) in MPCVD Diamond
Section titled âTechnical Documentation: Voltage Detected Single Spin Dynamics (SVDMR) in MPCVD DiamondâThis documentation analyzes the research demonstrating Surface Voltage Detected Magnetic Resonance (SVDMR) in diamond NV centers, providing technical specifications and outlining how 6CCVDâs advanced MPCVD diamond materials and fabrication services can support and scale this critical quantum technology.
Executive Summary
Section titled âExecutive SummaryâThe research successfully introduces Surface Voltage Detected Magnetic Resonance (SVDMR), a novel, non-optical method for reading out the spin state of single Nitrogen-Vacancy (NV) centers in diamond at ambient conditions.
- Core Achievement: Demonstrated coherent spin dynamics detection (Rabi oscillations) and magnetic resonance (SVDMR) by measuring spin-dependent changes in the diamond surface photovoltage (PV) using Kelvin Probe Force Microscopy (KPFM).
- Material Basis: Utilizes shallow NV centers (approx. 7 nm below the surface) created in thin, electronic grade CVD diamond substrates.
- Technological Advantage: SVDMR simplifies quantum sensor design by relying on voltage detection rather than current detection, eliminating the need for low contact resistance at the sample-electrode interface.
- Key Mechanism: The measured PV signal is dependent on the NV centerâs electron spin state, which influences the charge carrier cycling dynamics and subsequent trapping at surface states.
- Novel Detection: The technique successfully detected a non-fluorescing defect via surface voltage contrast, highlighting its potential for identifying novel defect centers beyond standard photoluminescence (PL) methods.
- Scalability: This voltage-based readout is highly promising for integrated quantum sensing and computing applications, offering a pathway toward faster (nanosecond-scale) capacitive measurements.
Technical Specifications
Section titled âTechnical SpecificationsâHard data extracted from the experimental methodology and results.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Substrate Thickness | 50 | ”m | Thin electronic grade CVD plate |
| Diamond Substrate Dimensions | 3 x 3 | mm | Custom size plate |
| NV Center Depth (Shallow) | 7 | nm | Below the diamond surface |
| Nitrogen Implantation Energy | 5 | keV | For NV creation |
| Nitrogen Implantation Dose | 5 x 109 | ions/cm2 | Low dose for single NV isolation |
| Excitation Wavelength | 520 | nm | Continuous Wave (CW) Green Laser |
| KPFM Detection Mode | Frequency-Modulated | N/A | Sideband KPFM |
| KPFM AC Potential Amplitude | 6 | V | $V_{ac}$ applied to cantilever |
| KPFM AC Potential Frequency | 3 | kHz | $f_{ac}$ for lock-in detection |
| SVDMR Contrast (Maximum) | -4.0 | % | PV detection contrast (Single NV) |
| PV-Detected Rabi Contrast (Maximum) | -2.0 | % | Coherent spin dynamics |
| Annealing Temperature (Maximum) | 1000 | °C | Post-implantation NV activation |
Key Methodologies
Section titled âKey MethodologiesâThe experimental procedure focused on high-purity material preparation, precise defect engineering, and advanced scanning probe microscopy.
- Material Preparation: A thin (50 ”m) electronic grade CVD diamond plate was used, requiring high crystalline quality for subsequent implantation.
- Defect Engineering: Shallow single NV centers were created via low-energy (5 keV) nitrogen ion implantation at a low dose ($5 \times 10^9$ ions/cm2).
- NV Activation: Post-implantation annealing was performed in a multi-step process, ramping up to 1000 °C for 2 hours to activate the NV centers.
- Surface Cleaning: The diamond surface was cleaned using a tri-acid mixture (nitric, perchloric, and sulphuric acids) to ensure a clean, stable surface environment critical for surface voltage detection.
- Electrode Fabrication: Gold (Au) micro-strip lines were deposited on the surface (using a Chromium sacrificial layer) to serve as electrical grounding and for applying the necessary Microwaves (MW) for spin manipulation.
- SVDMR Readout: Measurements were conducted using a combined Confocal-AFM setup. The KPFM signal (surface potential) was correlated with the applied MW frequency (SVDMR) or MW pulse length (Rabi oscillations) under continuous 520 nm laser illumination.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe SVDMR technique relies fundamentally on high-quality, precisely engineered diamond materials. 6CCVD is uniquely positioned to supply the necessary substrates and integrated fabrication services required to replicate, scale, and advance this research.
| Research Requirement | 6CCVD Solution & Value Proposition |
|---|---|
| Electronic Grade Diamond Substrates | Optical Grade Single Crystal Diamond (SCD): We provide high-purity, low-strain SCD substrates (Type IIa) essential for creating high-coherence NV centers via implantation. Our SCD material minimizes bulk defects, ensuring the surface voltage signal is dominated by the engineered shallow NV centers and surface states. |
| Custom Dimensions and Thickness | Precision Manufacturing: The 3 mm x 3 mm x 50 ”m geometry is standard for our custom cutting services. 6CCVD offers SCD plates in thicknesses from 0.1 ”m up to 500 ”m, allowing researchers to precisely control substrate geometry for integration into complex AFM/KPFM setups. We also offer substrates up to 10 mm thick. |
| Ultra-Shallow NV Creation | Optimized Polishing (Ra < 1 nm): Achieving shallow NV centers (7 nm depth) requires an atomically smooth surface. 6CCVD guarantees SCD polishing to Ra < 1 nm, which is critical for minimizing implantation straggle and maximizing the coherence of near-surface NV centers required for SVDMR. |
| Integrated Electrode Fabrication | In-House Metalization Services: The experiment required precise Au micro-strip lines for MW delivery and grounding. 6CCVD offers internal metalization capabilities, including Au, Ti, Pt, Pd, W, and Cu, allowing for custom, lithographically defined electrode patterns directly on the diamond surface, streamlining device fabrication. |
| Scaling to Polycrystalline Diamond (PCD) | Large Area PCD Wafers: While this study used SCD, 6CCVD offers high-quality Polycrystalline Diamond (PCD) wafers up to 125 mm in diameter, polished to Ra < 5 nm. This provides a scalable platform for ensemble SVDMR experiments or large-area quantum sensing arrays. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in material science for quantum applications. We can assist researchers in optimizing material selection for Surface Voltage Detected Magnetic Resonance (SVDMR) projects, including:
- Selecting the optimal SCD orientation and purity for specific ion implantation recipes.
- Designing custom metalization stacks (e.g., Ti/Pt/Au) for enhanced microwave delivery and electrical contact stability.
- Consulting on surface termination strategies to control carrier capture rates and enhance the measured photovoltage signal contrast.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Defect centres in crystals like diamond or silicon find a wide application in quantum technology, where the detection and control of their quantum states is crucial for their implementation as quantum sensors and qubits. The quantum information is usually encoded in the spin state of these defect centres, but they also often possess a charge which is typically not utilized. We report here the detection of elementary charges bound to single nitrogen-vacancy (NV) centres several nanometres below the diamond surface using Kelvin Probe Force Microscopy (KPFM) under laser illumination. Moreover, the measured signal depends on the NVâs electron spin state, thus allowing to perform a non-optical single spin readout, a technique we refer to as âSurface Voltage Detected Magnetic Resonanceâ (SVDMR). Our method opens a way of coherent spin dynamics detection for quantum sensing applications and could be potentially applied to other solid state systems. We believe that this voltage-based readout would help to simplify the design of devices for quantum technology.