Photoactivation of NV Centers in Diamond via Continuous Wave Laser Illumination of Shallow As‐Implanted Nitrogen
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2025-05-02 |
| Journal | Advanced Functional Materials |
| Authors | Jens Fuhrmann, Christoph Findler, Michael Olney‐Fraser, Lev Kazak, Fedor Jelezko |
| Institutions | Center for Integrated Quantum Science and Technology |
| Citations | 2 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Photoactivation of NV Centers in Diamond
Section titled “Technical Documentation & Analysis: Photoactivation of NV Centers in Diamond”This document analyzes the research paper “Photoactivation of NV Centers in Diamond via Continuous Wave Laser Illumination of Shallow As-Implanted Nitrogen” and outlines how 6CCVD’s advanced MPCVD diamond materials and customization services directly support and enable the replication and scaling of this quantum technology.
Executive Summary
Section titled “Executive Summary”This research successfully demonstrates a novel, scalable method for creating stable, negatively charged Nitrogen-Vacancy (NV-) centers in diamond, bypassing the traditional, lengthy high-temperature thermal annealing step.
- Novel Activation Method: Stable NV- centers are created using shallow 5 keV 15N+ ion implantation followed solely by Continuous Wave (CW) 405 nm laser photoactivation.
- Material Requirement: The study utilized electronic-grade Type IIa Single Crystal Diamond (SCD) substrates, confirming the necessity of high-purity, low-nitrogen material for optimal quantum performance.
- High Coherence Times: Single NV- emitters achieved Hahn echo T2 coherence times up to (331 ± 30) µs, demonstrating that photoactivation yields coherent properties comparable to conventional thermal annealing methods.
- Scalable Yield: A creation yield of (6 ± 3)% was achieved for the lowest implantation dose (1 x 109 15N+ cm-2), which is competitive with state-of-the-art techniques for shallow NV creation.
- Charge Stability: The photoactivated NV- centers exhibited excellent long-term charge stability, showing no blinking behavior over 104 days of observation.
- 6CCVD Value Proposition: 6CCVD provides the necessary high-purity SCD substrates, custom dimensions, and advanced polishing (Ra < 1 nm) required to optimize the shallow implantation and photoactivation process for integrated quantum devices.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the research paper detailing the material and process parameters:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Substrate Material | Type IIa SCD | N/A | Electronic-grade, (100) face orientation |
| Substrate Dimensions | 2 x 2 x 0.5 | mm3 | Commercial sample size used |
| Implantation Species | 15N+ | N/A | Used for NV center formation |
| Implantation Energy | 5 | keV | Shallow implantation |
| Implantation Dose Range | 1 x 109 to 1 x 1016 | 15N+ cm-2 | Logarithmic spacing |
| Median NV Depth | 12 ± 4 | nm | Shallow NV center location |
| Activation Laser Wavelength | 405 | nm | Continuous Wave (CW) laser |
| Activation Laser Power Range | 50 to 1300 | µW | Measured in front of NA = 0.95 objective |
| PL Saturation Power (405 nm) | ~800 | µW | Threshold for efficient activation |
| Maximum Hahn Echo T2 | 331 ± 30 | µs | Lowest implantation dose (single emitters) |
| Median Hahn Echo T2 | 49 ± 42 | µs | Shallow implanted NV centers |
| NV- Creation Yield (Min Dose) | 6 ± 3 | % | For 1 x 109 15N+ cm-2 |
| Estimated Surface Temperature Increase | ~114 | °C | Maximum temperature during activation (1300 µW, 32 min) |
Key Methodologies
Section titled “Key Methodologies”The photoactivation technique relies on precise material preparation and controlled laser exposure, bypassing the need for high-temperature annealing (> 800 °C).
- Substrate Cleaning and Preparation:
- Commercial Type IIa SCD was cleaned using a boiling 1:1:1 triacid mixture (sulfuric, perchloric, and nitric acid) at 170 °C for 30 minutes.
- This wet oxidation process ensured a contamination-free, oxygen-terminated diamond surface, critical for charge stability.
- Shallow Ion Implantation:
- 15N+ ions were implanted at 5 keV to achieve a shallow median depth of 12 nm.
- Doses spanned seven orders of magnitude (1 x 109 to 1 x 1016 15N+ cm-2) to study yield dependency.
- CW Laser Photoactivation:
- A 405 nm CW laser diode was used in a confocal microscope setup.
- Activation was performed by exposing implanted regions to laser powers between 50 µW and 1300 µW for up to 32 minutes per spot.
- Spectroscopic Characterization:
- Activated spots were probed using a 532 nm laser (300 µW) to measure Photoluminescence (PL) intensity.
- PL spectra confirmed the characteristic NV- Zero Phonon Line (ZPL) at 637 nm.
- Quantum Coherence Measurement:
- Electron spin coherence properties (T2, T, T1) were measured using pulsed optically detected magnetic resonance (ODMR) at an external magnetic field of B ≈ 500 G.
- Single NV- centers were confirmed via anti-bunching dip (g(2)(τ=0) < 0.5).
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”This research highlights the critical role of high-quality, ultra-pure diamond substrates in achieving high-performance quantum emitters. 6CCVD is uniquely positioned to supply the necessary materials and customization required to scale this photoactivation technique for commercial quantum applications.
Applicable Materials
Section titled “Applicable Materials”The success of shallow NV creation and long coherence times is directly dependent on the purity and surface quality of the diamond.
- Electronic Grade Single Crystal Diamond (SCD):
- Requirement: The paper used Type IIa electronic-grade SCD. This material is essential as its extremely low native nitrogen concentration minimizes background noise and maximizes the coherence time (T2) of the implanted NV centers.
- 6CCVD Solution: We offer high-purity SCD plates with guaranteed low substitutional nitrogen content, ideal for quantum sensing and computing applications.
- Isotope Control (12C Overgrown Samples):
- Requirement: The paper noted testing an overgrown sample with a 100 nm thick 12C enriched diamond layer. Isotope purification is crucial for extending T2 coherence times.
- 6CCVD Solution: We supply SCD substrates with custom-grown, isotopically purified 12C epitaxial layers, tailored to specific thickness requirements (0.1 µm to 500 µm) for optimal shallow NV performance.
Customization Potential for Integrated Devices
Section titled “Customization Potential for Integrated Devices”Scaling this photoactivation method requires substrates that fit into complex device architectures, often necessitating custom dimensions and integrated metal contacts.
| Research Requirement | 6CCVD Customization Capability | Technical Advantage |
|---|---|---|
| Substrate Size | Custom plates/wafers up to 125 mm (PCD equivalent size). | Enables scaling from small research samples (2x2 mm3) to wafer-level fabrication for commercial quantum chips. |
| Surface Quality | Ultra-low roughness polishing: Ra < 1 nm (SCD). | Essential for shallow implantation (12 nm depth) to minimize surface noise and maximize T2 coherence times. |
| Device Integration | Custom metalization services (Au, Pt, Pd, Ti, W, Cu). | Future integration requires electrodes (e.g., for charge state control or high voltage application, as discussed in the paper). 6CCVD provides in-house deposition of multi-layer metal stacks. |
| Thickness Control | SCD thickness control from 0.1 µm up to 500 µm. | Allows engineers to select optimal substrate thickness for thermal management and integration into photonic nanostructures. |
Engineering Support
Section titled “Engineering Support”The photoactivation process relies on optimizing the local charge environment, implantation dose, and surface morphology—complex variables requiring expert knowledge.
- Material Selection Consultation: 6CCVD’s in-house PhD team specializes in defect engineering and can assist researchers in selecting the optimal SCD grade and isotopic purity to maximize NV- creation yield and T2 coherence for similar quantum sensing and integrated photonics projects.
- Process Optimization: We provide technical guidance on surface preparation protocols (e.g., acid cleaning vs. plasma treatment) to ensure the diamond surface is optimally terminated for subsequent shallow implantation and photoactivation.
- Global Logistics: We offer reliable global shipping (DDU default, DDP available) to ensure high-value SCD substrates reach implantation facilities and research labs worldwide efficiently and securely.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Negatively charged nitrogen‐vacancy (NV − ) centers in diamond are appealing for quantum sensing applications due to their environmental sensitivity and long coherence times. Precise and scalable shallow color center creation is essential yet challenging for technological quantum applications. This is due to the involvement of several lengthy processes, such as ion implantation and thermal annealing of the samples. The latter process can be addressed by application of an alternative activation technique that bypasses the high‐temperature annealing. For this, nitrogen‐implanted regions on a diamond substrate are exposed to continuous‐wave 405 nm laser radiation. The illumination leads to local activation of NV − centers with photoluminescence yield saturation for regions activated with laser power at around 800 µW. For low implantation doses, single NV − centers are created with corresponding mean T 2 coherence time value around 71 µs. The NV − creation yield for the lower implantation doses match conventional creation methods, while higher doses show reduced yield values. However, the coherent properties are comparable to NV − centers within annealed samples. This shows that the activated NV − centers are well‐suited for advanced applications in quantum sensing and related technologies.