Rapid Growth of Single Crystal Diamond at High Energy Density by Plasma Focusing

At a Glance

Metadata	Details
Publication Date	2023-01-01
Journal	Journal of Inorganic Materials
Authors	Yicun LI, Xuedong LIU, Xiaobin Hao, Bing Dai, Jilei Lyu
Institutions	Harbin Institute of Technology
Citations	2
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Rate SCD Growth via Plasma Focusing

Executive Summary

This research successfully demonstrates a significant breakthrough in Single Crystal Diamond (SCD) growth kinetics by utilizing a novel plasma focusing structure optimized through Magnetohydrodynamic (MHD) simulation. This technical documentation outlines the key findings and highlights how 6CCVD’s advanced MPCVD diamond materials and customization capabilities can support and extend this high-rate growth technology.

Record Growth Rate: Achieved an ultra-high SCD growth rate of 97.5 µm/h, nearly 10 times faster than conventional methods tested in the same study (9.5 µm/h).
High Energy Density: A plasma energy density of 793.7 W/cm³ was realized by designing a conical focusing structure, representing a 3.9x increase over standard molybdenum disk setups.
Process Stability: High energy density was achieved under conventional, stable MPCVD parameters (3500 W, 18 kPa), avoiding the instability issues associated with high-pressure growth.
Plasma Enhancement: Simulation confirmed that the focusing structure increased the core electric field and electron density by approximately 3 times.
Material Quality: The resulting SCD films maintained high crystal quality, exhibiting sharp Raman peaks and controlled morphology, with nitrogen doping successfully inducing NV color centers.
6CCVD Value Proposition: 6CCVD is uniquely positioned to supply the necessary high-purity SCD seeds, custom dimensions (up to 125mm), and specialized doping (BDD, N-doping) required to scale and commercialize this high-speed MPCVD technique.

Technical Specifications

The following hard data points were extracted from the experimental results and simulation analysis:

Parameter	Value	Unit	Context
Maximum SCD Growth Rate	97.5	µm/h	Achieved using Focusing Structure + 300 ppm N₂
Baseline SCD Growth Rate	9.5	µm/h	Standard Molybdenum Disk, 0 ppm N₂
Plasma Energy Density (Focusing)	793.7	W/cm³	3.9x higher than standard setup
Microwave Power	3500	W	Conventional operating condition (2.45 GHz)
Growth Pressure	18	kPa	Equivalent to 135 Torr
Substrate Temperature	900	°C	Controlled via substrate stage height
Methane Concentration (CH₄/H₂)	5	%	10 sccm CH₄ in 190 sccm H₂
Nitrogen Doping Concentration	300	ppm	Used to enhance growth rate and induce NV centers
Core E-Field Enhancement	~3	times	Compared to standard Mo disk simulation
Core Electron Density Enhancement	~3	times	Compared to standard Mo disk simulation
Seed Dimensions	5 x 5 x 0.5	mm	CVD Single Crystal Diamond, (100) orientation
Raman Peak Position (S4)	1331.6	cm⁻¹	Shifted from ideal 1332.5 cm⁻¹ due to N₂-induced stress

Key Methodologies

The high-rate SCD growth was achieved through a systematic approach combining advanced simulation, custom hardware design, and optimized process parameters:

MHD Simulation and Optimization: Magnetohydrodynamic (MHD) modeling (using COMSOL) was performed to simulate the plasma properties, optimizing the reactor geometry (including the water-cooled stage and focusing structure dimensions) to maximize the core electric field and electron density.
Plasma Focusing Structure Design: A conical focusing structure, constructed from high-purity aluminum, was designed based on simulation results and integrated as a boundary condition within the MPCVD resonant cavity.
Growth Experiment Setup: SCD homoepitaxial growth was conducted on 5mm x 5mm (100) SCD seeds. The substrate temperature was maintained at 900 °C.
Process Parameter Control: Experiments were run at a fixed microwave power (3500 W) and pressure (18 kPa), utilizing a 5% CH₄ concentration in H₂.
Nitrogen Doping: Controlled amounts of N₂ (up to 300 ppm) were introduced to further enhance growth kinetics and modify surface morphology, successfully achieving the maximum growth rate (97.5 µm/h).
Plasma Diagnostics: Optical Emission Spectroscopy (OES) and plasma imaging (using an Hα filter) were used to characterize the plasma, confirming the increased concentration of growth-related radicals (atomic hydrogen, Hα) and verifying the effective plasma volume calculation for energy density determination.
Material Characterization: Grown films were analyzed using optical microscopy for surface morphology (observing step-flow growth in undoped samples and smoother surfaces in N₂-doped samples) and 532 nm Raman spectroscopy to confirm crystal quality and detect NV color centers.

6CCVD Solutions & Capabilities

The success of this research hinges on precise material control, high-quality seed crystals, and specialized reactor components. 6CCVD is an ideal partner to replicate, scale, and commercialize this high-rate SCD technology.

Applicable Materials for High-Rate Growth

To replicate or extend this high-energy density research, 6CCVD recommends the following materials:

6CCVD Material	Specification	Application in Research Context
Optical Grade SCD	High purity, low defect density, Ra < 1 nm polishing.	Ideal seed material (5mm x 5mm or larger) to ensure high-quality homoepitaxial growth at high speeds, minimizing defect propagation.
Nitrogen-Doped SCD	Custom N₂ concentration control (e.g., 300 ppm equivalent).	For high-speed growth kinetics and controlled synthesis of NV color centers, critical for quantum applications derived from this method.
Custom Substrates	SCD or PCD substrates up to 10 mm thickness.	Provides robust, thermally stable platforms for high-power, high-temperature reactor environments (900 °C).

Customization Potential & Engineering Services

The research utilized specific seed dimensions and custom reactor components. 6CCVD’s in-house capabilities directly address these needs:

Custom Dimensions and Thickness: While the paper used 5mm x 5mm seeds, 6CCVD can supply SCD plates up to 500 µm thick and PCD wafers up to 125 mm in diameter. We can provide larger SCD seeds (e.g., 10mm x 10mm or 15mm x 15mm) to scale up the high-rate growth area.
Precision Polishing: The quality of the seed surface is critical for step-flow growth. 6CCVD guarantees ultra-smooth polishing, achieving Ra < 1 nm on SCD surfaces, ensuring optimal starting conditions for high-speed epitaxy.
Metalization Services: Although the focusing structure was aluminum, future high-power reactor designs may require specialized electrical contacts or thermal management layers on the diamond substrate. 6CCVD offers internal metalization capabilities, including Ti, Pt, Au, Pd, W, and Cu deposition.
Engineering Support for Reactor Optimization: The core of this research is complex MHD simulation and reactor design. 6CCVD’s in-house PhD team specializes in MPCVD kinetics and material science and can assist researchers in optimizing material selection (e.g., substrate holder material, doping levels) for similar high-energy density plasma projects or specific NV color center synthesis applications.

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

View Original Abstract

Single crystal diamond is a kind of crystal material with excellent performance, which has important application value in advanced scientific field.In the field of single crystal diamond growth by microwave plasma chemical vapor deposition (MPCVD), improvement of crystal growth rate is still a key challenge, although corrent high energy density plasma has been a ralatively effective method.In this work, a special plasma focusing structure was designed through magnetohydrodynamic (MHD) model simulation which then was used in the growth experiment

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Original Source

DOI: https://doi.org/10.15541/jim20220633