Формирование многослойных наноструктур NV-центров в монокристаллическом CVD-алмазе

At a Glance

Metadata	Details
Publication Date	2020-01-01
Journal	Письма в журнал технической физики
Authors	А.М. Горбачев, М.А. Лобаев, Д.Б. Радищев, А.Л. Вихарев, С.А. Богданов
Analysis	Full AI Review Included

Technical Documentation and Analysis: Multilayer NV-Center Nanostructures in Single-Crystal CVD Diamond

Executive Summary

This research demonstrates a critical advancement in quantum material engineering: the successful fabrication of multilayer nitrogen-vacancy (NV) center nanostructures in single-crystal diamond (SCD) using Microwave Plasma Chemical Vapor Deposition (MPCVD).

Core Achievement: Creation of periodic, nitrogen-doped delta-layers within SCD, achieving unprecedented interface sharpness.
Interface Quality: Demonstrated extremely sharp layer boundaries, measured at less than 1 nm via Secondary Ion Mass Spectrometry (SIMS) depth profiling.
Quantum Performance: The multilayer structures significantly increase the concentration of practically useful NV^- centers, resulting in high photoluminescence (PL) intensity.
Coherence Time (T₂): Spin coherence times (T₂) were maintained at values comparable to uniformly doped layers, reaching up to 7.0 µs.
Methodology: Precise control of the MPCVD process, utilizing low methane concentration (0.15%) for slow growth and atomically smooth surfaces, combined with periodic nitrogen gas pulsing.
Application Relevance: These structures are highly desirable for next-generation quantum sensors, high-resolution magnetometers, and quantum information processing devices requiring high NV density near the surface.

Technical Specifications

The following hard data points were extracted from the research paper detailing the growth conditions and resulting material properties.

Parameter	Value	Unit	Context
Substrate Type	HPHT Type Ib (100)	N/A	Low initial N concentration (< 10¹⁵ cm^-3)
Substrate Miscut Angle	0.8-1.2	°	Required for high-quality SCD homoepitaxy
CVD Pressure	40	Torr	MPCVD growth condition
Total Gas Flow	950	sccm	Growth condition
Methane Concentration (C/H)	0.15	%	Ensures slow growth and low surface roughness
Nitrogen Doping Range (N/C)	0.5-1.5	%	Used for delta-layer formation
Achieved Interface Sharpness	< 1	nm	Measured via SIMS (critical for quantum applications)
Max Spin Coherence Time (T₂)	7.0	µs	Achieved in multilayer sample NV7
Layer Thickness Range (Samples S39, S17, NV7)	9-12	nm	Thickness of individual doped layers
Layer Period Range (Samples S39, S17, NV7)	39-68	nm	Distance between doped layers
Max N Concentration (in layer)	10 x 10¹⁸	cm^-3	Achieved in uniformly doped reference sample S14
PL Excitation Wavelength	514	nm	DPSS laser source

Key Methodologies

The successful fabrication of these high-quality nanostructures relied on precise control over the MPCVD environment and advanced characterization techniques.

Substrate Preparation: HPHT Type Ib (100) substrates were used, requiring precise polishing to achieve a low miscut angle (0.8-1.2°) to ensure step-flow growth and minimize defects.
Slow Growth Regime: A very low methane concentration (0.15%) was maintained to ensure a slow CVD growth rate, resulting in atomically smooth surfaces and low roughness, which is essential for sharp interfaces.
Delta-Layer Doping: Nitrogen doping was achieved by periodically pulsing the N₂ gas flow (0.5-1.5% concentration) during the CVD process, creating nitrogen-rich layers separated by undoped diamond.
Depth Profiling (SIMS): Time-of-Flight Secondary Ion Mass Spectrometry (TOF.SIMS-5) was used to measure the nitrogen concentration profile versus depth. Crucially, the data was processed using a depth resolution function (DRF) correction to accurately confirm the < 1 nm interface sharpness.
Optical Characterization (PL): Photoluminescence (PL) spectroscopy was used to measure the intensity and ratio of the NV^- (637 nm) and NV⁰ (575 nm) zero-phonon lines (ZPLs), providing insight into the Fermi level position and NV formation efficiency.
Quantum Characterization (T₂): Spin coherence time (T₂) measurements were performed using a confocal microscope setup and a 2-loop antenna (200 µm diameter) for electron spin manipulation via pulsed ODMR (Optically Detected Magnetic Resonance).

6CCVD Solutions & Capabilities

The research highlights the critical need for ultra-high-quality, precisely engineered SCD material—a core competency of 6CCVD. We are uniquely positioned to replicate and advance this work for quantum technology developers.

Applicable Materials

To replicate or extend this research, 6CCVD recommends the following materials:

Quantum Grade Single Crystal Diamond (SCD): Required for high-coherence NV-center formation. We offer high-purity SCD wafers with extremely low background nitrogen concentration (< 10¹⁵ cm^-3) necessary for controlled delta-layer doping.
Precision (100) Substrates: We supply SCD substrates with specified (100) orientation and controlled miscut angles (e.g., 0.8° to 1.2°) to ensure the step-flow growth regime critical for achieving atomically smooth surfaces and sharp interfaces (< 1 nm).
Custom Doping Profiles: 6CCVD specializes in advanced MPCVD growth recipes, allowing for the precise control of nitrogen pulsing required to create periodic delta-layers with customizable thickness (9 nm to 500 µm) and period (39 nm to 10 mm).

Customization Potential

The success of this research hinges on dimensional and structural precision, areas where 6CCVD excels:

Research Requirement	6CCVD Capability	Benefit to Client
Sharp Interfaces (< 1 nm)	Advanced MPCVD control and low C/H ratio recipes.	Guaranteed material quality necessary for high-fidelity quantum sensing.
Custom Layer Thickness/Period	SCD thickness control from 0.1 µm to 500 µm.	Ability to tune layer parameters (e.g., 9 nm thickness, 68 nm period) to optimize T₂ and NV^- intensity for specific applications.
Large Area Wafers	Plates/wafers up to 125 mm (PCD) and large-area SCD.	Scalability for industrial production of quantum devices and sensors.
Surface Finish	Polishing capability to achieve Ra < 1 nm (SCD).	Ensures the required atomic smoothness for subsequent device fabrication and characterization.
Metalization	Internal capability for custom metal contacts (Au, Pt, Ti, W, etc.).	Essential for integrating microwave antennas (like the 200 µm antenna used in the paper) directly onto the diamond surface for ODMR measurements.

Engineering Support

The trade-off between maximizing NV^- center density (high PL signal) and preserving spin coherence time (T₂) is complex. The paper demonstrates that optimizing the layer period (e.g., moving from 39 nm to 68 nm) can significantly improve T₂.

6CCVD’s in-house PhD team offers expert consultation on material selection and growth recipe optimization for similar Quantum Sensing and Magnetometry projects. We assist clients in designing custom delta-layer structures to balance high signal intensity with long coherence times, ensuring optimal performance for their specific device architecture.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Results of synthesis of multilayered nitrogen doped nanostructures, which consist of periodically located nitrogen-containing layers in monocrystalline CVD diamond, are presented. The possibility of creation of nitrogen doped layers with extremely abrupt interfaces, less than 1 nm, is demonstrated. Photoluminescence studies have shown that multilayered structures allow obtaining higher emission intensity of practically important NV- centers with spin coherence times close to homogeneously doped layers at the same nitrogen concentration.

Tech Support

Original Source

DOI: https://doi.org/10.21883/pjtf.2020.13.49585.18299