Effect of Nitrogen on Growth and Optical Properties of Single-Crystal Diamond Synthesized by Chemical Vapor Deposition

At a Glance

Metadata	Details
Publication Date	2024-03-12
Journal	Materials
Authors	Ying Ren, Wei Lv, Xiaogang Li, Haoyong Dong, Nicolas Wöhrl
Institutions	Shenzhen Institutes of Advanced Technology, Henan University of Technology
Citations	8
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Rate SCD Growth via Nitrogen Doping

This document analyzes the research paper “Effect of Nitrogen on Growth and Optical Properties of Single-Crystal Diamond Synthesized by Chemical Vapor Deposition” to provide technical specifications and align the findings with 6CCVD’s advanced MPCVD diamond manufacturing capabilities.

Executive Summary

This study successfully demonstrates a method for achieving high-speed, high-quality Single Crystal Diamond (SCD) growth using Microwave Plasma Chemical Vapor Deposition (MPCVD) by precisely controlling nitrogen (N₂) doping.

4.5x Growth Rate Enhancement: The introduction of N₂ increased the SCD growth rate from 10 µm/h (undoped) to a stabilized maximum of 45.5 µm/h, representing a 4.5-fold enhancement.
Optimal Doping Identified: Maximum growth rate was achieved within a narrow N₂/H₂ doping range of 0.8% to 1.2%.
NV Center Activation: Nitrogen doping facilitated the formation of Nitrogen-Vacancy (NV) centers (NV⁰ at 575 nm and NV^- at 637 nm), indicating that NV centers activate the diamond lattice and accelerate chemical reaction rates.
Growth Mode Transition: N₂ addition shifted the growth mechanism from the typical step-flow mode to bi-dimensional nucleation, resulting in increased step density and pyramidal hillock formation.
Crystalline Quality Retention: Despite the high growth rate and increased internal stress, Raman analysis confirmed minimal degradation in crystalline quality, with the Full-Width-at-Half-Maximum (FWHM) remaining low (3.1 to 4.1 cm^-1).
Microscopic Bonding Confirmation: X-ray Photoelectron Spectroscopy (XPS) confirmed the presence of C-N bonds and the emergence of non-diamond sp² C-C bonding at higher doping levels (0.8% N₂/H₂).

Technical Specifications

The following hard data points were extracted from the experimental results, focusing on the optimal growth conditions (Sample S4, 1.2% N₂/H₂).

Parameter	Value	Unit	Context
Maximum Growth Rate	45.5	µm/h	Achieved at 1.2% N₂/H₂ doping
Growth Rate Factor	4.5	Factor	Enhancement compared to undoped SCD (10 µm/h)
Optimal N₂ Doping	0.8 - 1.2	% (N₂/H₂)	Range for stabilized maximum growth
Substrate Temperature	~950	°C	Standard operating temperature
Plasma Power	~3.25	kW	Power used in the 5 kW, 2.45 GHz MPCVD system
Growth Pressure	~13	kPa	Equivalent to approximately 97.5 Torr
Raman FWHM Range	3.1 - 4.1	cm^-1	Indicative of high crystalline quality
Neutral NV Center ZPL	575	nm	Zero Phonon Line (ZPL) observed via PL/Raman
Negative NV Center ZPL	637	nm	Zero Phonon Line (ZPL) observed via PL/Raman
Substrate Material	Ib (100) SCD	3.8 x 3.8 x 1 mm³	Used as seed crystal

Key Methodologies

The experiment utilized a high-power MPCVD system to synthesize SCDs under controlled gas flow and temperature conditions.

Substrate Preparation: Commercial High-Temperature, High-Pressure (HTHP) Ib (100) SCD seeds (3.8 x 3.8 x 1 mm³) were cleaned and subjected to a 30-minute H₂ plasma etch (300 sccm H₂, 12 kPa) to eliminate surface defects prior to growth.
MPCVD System: A 5 kW, 2.45 GHz MPCVD reactor was employed for the 4-hour homoepitaxial growth process.
Fixed Gas Parameters: H₂ flow rate was fixed at 300 sccm, and CH₄ flow rate was fixed at 24 sccm (CH₄/H₂ ratio of 8%).
Variable Doping: N₂ flow rates were varied from 0 sccm up to 4.5 sccm, corresponding to N₂/H₂ doping levels from 0% to 1.5%.
Growth Conditions: The process was maintained at a temperature of approximately 950 °C, a pressure of ~13 kPa, and a plasma power of ~3.25 kW.
Characterization: Grown films were analyzed using Raman spectroscopy, Photoluminescence (PL) spectroscopy (532 nm laser excitation), and X-ray Photoelectron Spectroscopy (XPS) to assess crystalline quality, defect concentration, and bond structure.

6CCVD Solutions & Capabilities

The research highlights the critical need for precise doping control and high-quality SCD substrates for advanced applications, particularly in quantum sensing and optics. 6CCVD is uniquely positioned to supply the materials and processing required to replicate and scale this high-rate, NV-optimized growth.

Applicable Materials for Replication and Scaling

To replicate the high-rate growth and NV center optimization demonstrated in this paper, researchers require high-purity, low-strain SCD material with precise nitrogen control.

6CCVD Material Solution	Specification & Application	Relevance to Research
Optical Grade Single Crystal Diamond (SCD)	High-purity, low-birefringence material optimized for quantum and optical applications.	Ideal starting substrate (seed) for homoepitaxial growth requiring controlled defect incorporation (NV centers).
Custom Doped SCD	SCD grown with precise, controlled nitrogen incorporation (N₂/CH₄ ratios) to maximize NV^- concentration.	Directly addresses the paper’s core finding: achieving high growth rate and high NV concentration simultaneously.
Thick SCD Substrates	SCD plates available up to 500 µm thickness, or substrates up to 10 mm.	Necessary for scaling the 45 µm/h growth rate into robust, functional devices requiring significant material depth.

Customization Potential & Post-Processing Services

The high growth rate achieved (45.5 µm/h) resulted in a rough surface morphology characterized by pyramidal hillocks, which is detrimental to optical and electronic device fabrication. 6CCVD offers comprehensive post-processing solutions to address these challenges.

Ultra-Smooth Polishing: The rough surface morphology resulting from bi-dimensional nucleation necessitates post-growth planarization. 6CCVD provides SCD polishing services achieving surface roughness (Ra) < 1 nm, essential for subsequent device fabrication and optical clarity.
Custom Dimensions: While the paper used small 3.8 x 3.8 mm seeds, 6CCVD can supply custom-sized SCD wafers and large-area Polycrystalline Diamond (PCD) plates up to 125 mm in diameter, enabling industrial scaling of this high-rate process.
Advanced Metalization: For integrating NV-doped SCD into quantum devices (e.g., waveguides or electrodes), 6CCVD offers in-house custom metalization using materials including Au, Pt, Pd, Ti, W, and Cu.

Engineering Support

The successful synthesis of high-quality, NV-optimized diamond relies heavily on balancing gas chemistry, plasma power, and temperature—a complex parameter space.

6CCVD’s in-house PhD team specializes in MPCVD recipe optimization and can assist engineers and scientists with material selection and process design for similar Quantum Sensing and High-Rate Optical Diamond projects. We provide consultation on achieving specific defect concentrations (NV, SiV, etc.) and managing the trade-offs between growth rate and crystalline quality (FWHM).

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

View Original Abstract

Concurrently achieving high growth rate and high quality in single-crystal diamonds (SCDs) is significantly challenging. The growth rate of SCDs synthesized by microwave plasma chemical vapor deposition (MPCVD) was enhanced by introducing N2 into the typical CH4-H2 gas mixtures. The impact of nitrogen vacancy (NV) center concentration on growth rate, surface morphology, and lattice binding structure was investigated. The SCDs were characterized through Raman spectroscopy, photoluminescence (PL) spectroscopy, and X-ray photoelectron spectroscopy. It was found that the saturation growth rate was increased up to 45 μm/h by incorporating 0.8-1.2% N2 into the gas atmosphere, which is 4.5 times higher than the case without nitrogen addition. Nitrogen addition altered the growth mode from step-flow to bidimensional nucleation, leading to clustered steps and a rough surface morphology, followed by macroscopically pyramidal hillock formation. The elevation of nitrogen content results in a simultaneous escalation of internal stress and defects. XPS analysis confirmed chemical bonding between nitrogen and carbon, as well as non-diamond carbon phase formation at 0.8% of nitrogen doping. Furthermore, the emission intensity of NV-related defects from PL spectra changed synchronously with N2 concentrations (0-1.5%) during diamond growth, indicating that the formation of NV centers activated the diamond lattice and facilitated nitrogen incorporation into it, thereby accelerating chemical reaction rates for achieving high-growth-rate SCDs.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma17061311

References

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