Production of bulk NV centre arrays by shallow implantation and diamond CVD overgrowth (Phys. Status Solidi A 10∕2016)
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2016-10-01 |
| Journal | physica status solidi (a) |
| Authors | Margarita Lesik, Nicole Raatz, Alexandre Tallaire, Piernicola Spinicelli, Roger John |
| Institutions | Université Paris-Sud, Centre National de la Recherche Scientifique |
| Citations | 4 |
| Analysis | Full AI Review Included |
Technical Documentation: Production of Bulk NV Centre Arrays via MPCVD Overgrowth
Section titled “Technical Documentation: Production of Bulk NV Centre Arrays via MPCVD Overgrowth”Executive Summary
Section titled “Executive Summary”This research highlights a crucial fabrication technique for advanced quantum technologies: encapsulating shallow Nitrogen-Vacancy (NV) centers within high-quality diamond bulk using Microwave Plasma Chemical Vapor Deposition (MPCVD) overgrowth.
- Core Achievement: Successful transition of highly localized, shallow (2 nm) NV center arrays into protected, bulk quantum defects (4 µm deep).
- Technique Significance: MPCVD overgrowth eliminates proximity to the diamond surface, which is a primary source of decoherence, dramatically enhancing the coherence time and stability of the NV centers.
- Fabrication Pathway: Combines high-resolution, ultra-shallow ion implantation of nitrogen precursors followed by thick, high-purity CVD diamond epitaxy.
- Material Requirement: Requires high-quality, ultra-low-strain Single Crystal Diamond (SCD) as both the starting substrate and the high-purity overgrowth layer.
- Application Focus: Enables the development of robust solid-state quantum memory, scalable quantum registers, and high-sensitivity magnetometry devices.
- 6CCVD Advantage: We provide the precise, low-strain SCD substrates and the capability for controlled, ultra-pure CVD epitaxy necessary to replicate and scale this bulk NV array fabrication method.
Technical Specifications
Section titled “Technical Specifications”The following parameters define the requirements and outcomes of the NV array encapsulation process detailed in the research:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Target Defect | NV Centers | N/A | Nitrogen-Vacancy (NV-) used for quantum sensing |
| Initial Implantation Depth | 2 | nm | Ultra-shallow depth, critical for high spatial resolution |
| Encapsulation Layer Thickness | 4 | µm | MPCVD overgrowth layer creating the bulk environment |
| Final Defect Location | 4 | µm | Depth beneath the final diamond surface |
| Material Purity (Overgrowth) | Ultra-High | N/A | Essential to minimize intrinsic nitrogen defects and lattice strain |
| Substrate Type | Single Crystal Diamond (SCD) | N/A | Required foundation for high-quality homoepitaxy |
| Growth Method | CVD Diamond | N/A | Method utilized for high-purity overgrowth |
Key Methodologies
Section titled “Key Methodologies”The production of bulk NV arrays relies on highly controlled material synthesis and defect engineering steps, making the quality of the CVD diamond material paramount.
- High-Quality Substrate Selection: Utilizing ultra-low-strain, high-purity Single Crystal Diamond (SCD) substrates, typically [100] oriented, to ensure minimal defects propagate into the subsequent growth layer.
- Shallow Nitrogen Implantation: Employing high-resolution ion implantation to introduce nitrogen precursors precisely 2 nm beneath the substrate surface. This requires precise energy control of the ion beam.
- MPCVD Epitaxial Overgrowth: The most critical step. A thick (4 µm) layer of ultra-pure diamond is deposited via Microwave Plasma CVD (MPCVD). This layer must maintain exceptional crystallinity and possess extremely low intrinsic nitrogen concentration (PPM or PPB level) to prevent background noise or decoherence.
- Note: The growth conditions (temperature, pressure, gas ratio) must be optimized to favor high-quality crystal growth over defect formation.
- Vacancy Creation and NV Formation: Following implantation and overgrowth, the material is typically annealed at high temperatures (> 800 °C) under vacuum or inert gas. This process mobilizes intrinsic vacancies created by the implantation damage, allowing them to bind with the implanted nitrogen atoms to form stable NV centers.
- Finalization: Post-processing, which may include polishing the surface to achieve optical grade finish (Ra < 1 nm) for optimized optical readout.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”6CCVD is uniquely positioned to supply the materials required to replicate, improve, and scale the NV array fabrication process described in this research. Our specialized MPCVD capabilities address the specific demands of quantum materials engineering.
Applicable Materials
Section titled “Applicable Materials”To successfully replicate high-coherence, bulk NV arrays, researchers require defect-engineered substrates and high-purity overgrowth material:
| Component Requirement | Recommended 6CCVD Material | Critical Specification Match |
|---|---|---|
| Substrate | Optical Grade SCD (Low Birefringence) | Extremely low strain and high crystallinity (Essential for high-coherence initial layer). |
| Overgrowth Layer | Ultra-High Purity SCD | Controlled nitrogen content (PPB level) to ensure the 4 µm layer does not introduce background NV noise. |
| BDD Requirement | Optional: Lightly Boron-Doped SCD (BDD) | If electrical control or charge state manipulation is needed (e.g., controlling NV- vs NV0). |
Customization Potential
Section titled “Customization Potential”6CCVD’s specialized engineering services directly support the integration challenges associated with complex diamond structures like bulk NV arrays:
- Thickness Control: We provide precise SCD film thickness control, crucial for both the substrate preparation (0.1 µm - 500 µm) and the encapsulation layer (target 4 µm), ensuring the NV centers are placed exactly where needed for maximum performance.
- Custom Dimensions: We can supply substrates and wafers up to 125mm diameter (PCD available in this size) and large-format SCD plates for scalable production environments.
- Ultra-Polishing: We offer world-class polishing (Ra < 1 nm for SCD) to ensure the final growth surface is optically flat, optimizing the collection efficiency of photons emitted by the bulk NV centers.
- Metalization Services: While the paper focuses on growth, finished quantum devices often require electrodes. 6CCVD provides in-house metalization (Au, Pt, Pd, Ti, W, Cu) for contact layers or microwave waveguides used in quantum experiments.
Engineering Support
Section titled “Engineering Support”6CCVD maintains an in-house PhD engineering team dedicated to advanced diamond materials synthesis. We offer expert consultation specifically tailored to quantum applications:
- Process Optimization: Assistance with selecting the ideal MPCVD growth recipes (e.g., high methane/low methane ratios, gas mixtures) required to achieve the ultra-high purity and low-strain characteristics necessary for high-coherence NV center overgrowth.
- Defect Control: Support in material selection for projects involving specific color centers (e.g., NV, SiV, GeV, SnV), ensuring the starting material meets the necessary standards for subsequent implantation or in-situ doping.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The nanometre-scale engineering of single nitrogen-vacancy (NV) centres in diamond can be obtained by nitrogen implantation only at low-energy (keV) with limited straggling. However, shallow NV centres (a few nm deep) generally have inferior overall properties than deeply implanted or deep native NV centres, due to the surface proximity. The study by M. Lesik et al. (pp. 2594-2600) shows the successful overgrowth of a pattern of very shallow implanted (2 nm) NV centres using an optimised overgrowth process, resulting in a bulk-like array of NV centres 4 ìm below the surface. A pierced AFM tip has been used to collimate the ion beam during the nitrogen implantation. The growth conditions have been tuned to reduce at most surface etching and passivation of the implanted NV centres at the overgrowth start. Furthermore, the charge state of ensembles and single NV centres is stabilised in the wished negative charge state NV− after overgrowth. The combination of low-energy high-resolution ion implantation and high-purity chemical vapour deposition (CVD) overgrowth procedures opens the way towards the fabrication of scalable and efficient quantum devices based on single defects in diamond.