Interactions of Nitrogen‐Vacancy Centers in Diamond with Electron Beams - Implications for Quantum Sensing and Photoluminescence Stability
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2025-10-26 |
| Journal | Advanced Optical Materials |
| Authors | Bradley T. Flinn, William J. Cull, Ian Cardillo‐Zallo, James Kerfoot, Benjamin L. Weare |
| Institutions | University of Nottingham |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Interactions of Nitrogen-Vacancy Centers in Diamond with Electron Beams
Section titled “Technical Documentation & Analysis: Interactions of Nitrogen-Vacancy Centers in Diamond with Electron Beams”Executive Summary
Section titled “Executive Summary”This research provides critical insights into the stability and controlled manipulation of Nitrogen-Vacancy (NV) centers in diamond under electron beam irradiation, directly supporting the development of robust nanoscale quantum sensing and nanofabrication techniques.
- Core Mechanism Identified: Electron beam damage to NV photoluminescence (PL) and sensing contrast (ODMR/MM) is dominated by a complex interplay of ionization and Direct Knock-On (DKO) effects, leading to vacancy migration away from the nitrogen atom.
- Optimal Non-Invasive Conditions: For Correlative Light-Electron Microscopy (CLEM) applications requiring maximum NV retention, the optimal parameters are identified as 200 keV beam energy at a low electron fluence (< 10⁵ e⁻nm⁻²).
- Controlled Deactivation: High fluence irradiation (e.g., 9.0 x 10⁶ e⁻nm⁻² at 200 keV) successfully quenches PL and sensing contrast to near-zero levels (4% residual PL), enabling controlled, top-down spatial patterning of diamond PL.
- Material Sensitivity: Damage mechanisms occur well below the displacement energy thresholds for pristine bulk diamond, indicating high sensitivity in NV-rich nanodiamonds (FNDs) due to ionization-assisted DKO.
- 6CCVD Value Proposition: 6CCVD offers the high-purity Single Crystal Diamond (SCD) and large-area Polycrystalline Diamond (PCD) substrates necessary to replicate and scale this patterning methodology for integrated quantum devices.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the analysis of NV center stability under varying electron beam conditions:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Optimal E-Beam Energy (Non-Invasive) | 200 | keV | Recommended for CLEM (Fluence < 10⁵ e⁻nm⁻²) |
| Optimal Electron Fluence (Non-Invasive) | < 10⁵ | e⁻nm⁻² | Retains > 90% PL and sensing contrast |
| Maximum Fluence Tested | 9.0 x 10⁶ | e⁻nm⁻² | Highest damage condition |
| Residual PL (Max Damage) | 4 ± 1 | % | 200 keV, 9.0 x 10⁶ e⁻nm⁻² |
| Residual ODMR Contrast (Max Damage) | 5 ± 3 | % | 200 keV, 9.0 x 10⁶ e⁻nm⁻² |
| Carbon Displacement Energy ($E_{d}$) (Pristine Lattice) | 30 - 80 | eV | Literature range (requires 145-330 keV beam) |
| Carbon Displacement Energy ($E_{d}$) (Adjacent to Vacancy) | 2.3 - 13.0 | eV | Range used for DKO cross-section calculation |
| Maximum Transferable Energy ($E_{Tmax}$) | 43.7 | eV | Achieved by 200 keV beam |
| Displacement Cross Section ($\sigma_{d}$) ($E_{d}$ = 2.3 eV) | 329 | barn | 200 keV beam energy |
| Ionization Cross Section ($\sigma_{i}$) (C L shell) | 1.2 | Mbarn | 200 keV beam energy |
Note: 1 barn = 10⁻²⁸ m².
Key Methodologies
Section titled “Key Methodologies”The experimental approach combined high-resolution electron microscopy with quantum sensing techniques to precisely monitor NV center properties during irradiation.
- Material Preparation: Commercially available NV-rich Fluorescent Nanodiamonds (FNDs, ≈100 nm diameter, HPHT synthesis) were drop-cast onto Au holey carbon TEM finder grids.
- Irradiation Source: Transmission Electron Microscopy (TEM, JEOL 2100+) was used at four distinct accelerating voltages: 20, 80, 100, and 200 keV.
- Fluence Control: Electron fluence was systematically varied across seven orders of magnitude (≈10³ to 10⁷ e⁻nm⁻²) using a custom electron microscope script for precise exposure timing.
- Quantum Sensing (ODMR/MM): NV sensing contrast was monitored via Optically Detected Magnetic Resonance (ODMR) and Magnetic Modulation (MM) of Photoluminescence (PL) using a custom PCB with a Cu wire for microwave delivery (2.77-2.97 GHz) and an external electromagnet (0-40 mT).
- Optical Characterization: PL intensity and NV charge-state ratios (NV⁻ ZPL at 637 nm and NV⁰ ZPL at 575 nm) were mapped using a confocal Raman microscope before and after irradiation.
- Simulation & Analysis: Monte Carlo CASINO simulations were performed to model electron trajectories and interaction volumes in diamond, supporting calculations of atomic displacement ($\sigma_{d}$) and ionization ($\sigma_{i}$) cross-sections.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”This research validates a powerful top-down approach for engineering NV properties, moving beyond FNDs toward macroscopic diamond substrates for integrated quantum technologies. 6CCVD is uniquely positioned to supply the high-quality MPCVD diamond materials and customization services required to scale this methodology.
Applicable Materials for Replication and Extension
Section titled “Applicable Materials for Replication and Extension”To transition this nanoscale patterning technique to functional, integrated quantum devices, researchers require high-purity, low-strain diamond substrates with controlled nitrogen incorporation.
| Research Requirement | 6CCVD Material Solution | Key Specification |
|---|---|---|
| High Coherence/Low Strain | Optical Grade Single Crystal Diamond (SCD) | SCD wafers with Ra < 1 nm polishing, ideal for high-fidelity quantum sensing applications. |
| Scalable Patterning Substrates | Polycrystalline Diamond (PCD) | Plates/wafers up to 125 mm diameter, suitable for large-area nanofabrication and industrial scaling. |
| Controlled NV Creation | Custom Nitrogen-Doped SCD/PCD | Precise control over nitrogen concentration during MPCVD growth to optimize initial NV density prior to e-beam patterning. |
| Integrated Sensing | Boron-Doped Diamond (BDD) | Available for applications requiring conductive diamond layers or electrochemical sensing integration. |
Customization Potential for Advanced Quantum Devices
Section titled “Customization Potential for Advanced Quantum Devices”The paper highlights the need for precise control over material dimensions and integration features (e.g., microwave delivery lines). 6CCVD’s in-house capabilities directly address these requirements:
- Custom Dimensions and Thickness: 6CCVD supplies SCD and PCD plates/wafers in custom dimensions up to 125 mm (PCD). We offer precise thickness control for both SCD (0.1 µm - 500 µm) and PCD (0.1 µm - 500 µm), crucial for controlling the depth and volume of e-beam induced defects.
- Ultra-Low Surface Roughness: To ensure minimal scattering and optimal optical coupling for PL mapping and ODMR, 6CCVD provides superior polishing: Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD.
- Integrated Metalization: The experimental setup relied on external Cu wire for microwave delivery. 6CCVD offers internal metalization services (Au, Pt, Pd, Ti, W, Cu) directly onto diamond substrates, enabling the fabrication of integrated quantum devices with on-chip microwave transmission lines for enhanced ODMR/MM performance.
- Precision Fabrication: We offer custom laser cutting and shaping services to meet unique geometry requirements for TEM grids, PCB integration, or specific device architectures.
Engineering Support
Section titled “Engineering Support”6CCVD’s in-house PhD team specializes in MPCVD diamond growth and defect engineering. We provide authoritative professional support for projects involving:
- Material selection to optimize initial NV concentration and crystal quality for e-beam patterning.
- Consultation on surface preparation and polishing requirements for high-resolution CLEM and optical measurements.
- Guidance on integrating custom metalization schemes for advanced [Quantum Sensing and Nanofabrication] projects.
Call to Action: For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Nitrogen‐vacancy (NV) photoluminescence (PL) in diamond is fundamental to its function as a color center, underpinning advances in sensing science and quantum technologies. The work herein provides critical insights into the atomistic mechanisms of electron beams interacting with NV centers, which are crucial for advancing robust quantum sensing at the nanoscale and controlling the functional properties of nanodiamonds. NV PL and sensing stability of NV‐rich fluorescent nanodiamonds (FNDs) under electron beam irradiation is probed, across a range of energies (20, 80, 100, and 200 keV) and fluences (≈10 3 to 10 7 e − nm −2 ). PL intensity, NV charge‐state ratios, and sensing contrast, as monitored via optically detected magnetic resonance (ODMR) and magnetic modulation (MM) of PL, are examined. Results reveal complex mechanisms governing interactions between NV‐centers and fast electrons, dominated by ionization and direct knock‐on (DKO) effects, which allow to establish optimum imaging conditions where FNDs can be imaged with sub‐nanometer resolution while preserving their PL and sensing properties (200 keV, <10 5 e − nm −2 ). This methodology enables controlled, top‐down spatial patterning of diamond PL by selectively deactivating NVs, providing novel routes to patterned NV creation.