CVD Diamond Growth Enhanced by a Dynamic Magnetic Field

At a Glance

Metadata	Details
Publication Date	2023-02-15
Journal	Coatings
Authors	Xuezhang Liu, Kui Wen, Xiaohua Duan, Caihua Wang, Hangyu Long
Institutions	Jiangxi Science and Technology Normal University, Guangdong Academy of Sciences
Citations	3
Analysis	Full AI Review Included

CVD Diamond Growth Enhanced by a Dynamic Magnetic Field: Technical Analysis and 6CCVD Solutions

This document analyzes the research detailing the enhancement of CVD diamond growth using a Dynamic Magnetic Field (DMF) during Hot Filament CVD (HFCVD). It provides extracted technical specifications and outlines how 6CCVD’s advanced MPCVD capabilities can replicate, extend, and industrialize these findings, particularly addressing the challenges related to large-area uniformity.

Executive Summary

Growth Rate Enhancement: Introduction of a Dynamic Magnetic Field (DMF) significantly enhanced CVD diamond growth kinetics, achieving a maximum growth rate increase of approximately 2.5 times (from 0.62 µm/h to 1.53 µm/h) at 1023 K.
Crystallographic Control: The DMF successfully controlled the preferential orientation of Polycrystalline Diamond (PCD) films, evolving the texture from (110) to a fully (100) textured film by increasing the angular frequency to 150 $\pi$ rad/s.
High Quality Maintained: Diamond quality, characterized by the ratio ID/(ID + IG/50), remained high (typically > 0.97) across all tested angular frequencies, confirming that the DMF enhancement mechanism does not promote the formation of graphitic sp² carbon defects.
Mechanism: The enhancement is attributed to the DMF confining thermionically emitted electrons, leading to enhanced electron-molecule collisional excitation and activation of more gas molecules (CH${3}$ and C${2}$H$_{2}$) for diamond growth.
Uniformity Challenge: Uniform deposition on large-area substrates (15 mm x 15 mm) was not achieved due to the low magnetic field intensity (110 Gs) and severe substrate temperature fluctuation (a 200 K gradient from center to edge).
6CCVD Value Proposition: 6CCVD’s advanced MPCVD technology inherently solves the large-area uniformity and thermal gradient issues encountered in HFCVD, enabling the production of large-area, highly textured PCD wafers up to 125 mm.

Technical Specifications

Parameter	Value	Unit	Context
Maximum Growth Rate Achieved	1.53	µm/h	At 1023 K and 150 $\pi$ rad/s
Growth Rate Enhancement Factor	2.5	Times	Relative to 0 $\pi$ rad/s (HFCVD only) at 1023 K
Deposition Temperatures (T)	1023 ± 50, 1123	K	Substrate temperature monitored by thermocouple
Angular Frequencies (w) Tested	50, 100, 150 $\pi$	rad/s	Dynamic Magnetic Field (DMF) input
Magnetic Field Intensity (B)	110	Gs	Nominal intensity, decreased when frequency exceeded rated value
Precursor Gas Composition	2% CH${4}$ in H${2}$	Ratio	Methane diluted in Hydrogen
Total Gas Flow Rate	100	sccm	Standard Cubic Centimeters per Minute
Deposition Pressure	3	kPa	Low-pressure CVD environment
Achieved Crystallographic Texture	(100)	Orientation	Fully textured PCD film at 150 $\pi$ rad/s
Diamond Quality Ratio (Minimum)	0.97	Ratio	ID/(ID + IG/50) for 1023 K films
Substrate Temperature Gradient	200	K	Fluctuation from center (1023 K) to edge (823 K) on 15 mm substrate

Key Methodologies

The experiment utilized a modified Hot Filament Chemical Vapor Deposition (HFCVD) system coupled with an external Dynamic Magnetic Field (DMF) apparatus.

Substrate Preparation: Polished Silicon (Si) wafers (5 mm x 5 mm x 0.7 mm, or 15 mm x 15 mm x 0.7 mm for uniformity tests) were pretreated via ultrasonic bath using an aqueous solution of 1 µm diamond powder to enhance nucleation density.
Filament Setup: A 0.5 mm diameter Tungsten (W) wire was wrapped into seven coils and mounted on Molybdenum (Mo) electrodes, resistively heated to 2000-2400 °C.
Reactor Configuration: The substrate was placed 10 mm vertically below the filament. Deposition temperature was monitored via a thermocouple set on the center of the substrate back, maintained at 1023 K or 1123 K.
Gas Parameters: Methane (CH${4}$) was diluted to 2% in Hydrogen (H${2}$). The gas mixture was metered into the HFCVD chamber at a flow rate of 100 sccm.
Pressure Control: The deposition pressure was maintained at 3 kPa via evacuation using a vacuum pump.
DMF Application: A cylindrical winding of a three-phase stator was applied externally to the HFCVD chamber. A Variable-Frequency Drive (VFD) adjusted the input current frequency to excite the DMF at angular frequencies of 50, 100, and 150 $\pi$ rad/s.
Characterization: Film morphology, thickness, quality, and orientation were assessed using FE-SEM, spectroscopic ellipsometry, micro-Raman spectroscopy, and X-ray Diffractometry (XRD).

6CCVD Solutions & Capabilities

This research demonstrates the potential for external fields to enhance growth kinetics and control crystallographic orientation in PCD. 6CCVD, as an expert in MPCVD diamond synthesis, offers materials and engineering support that directly addresses the requirements and limitations identified in this study.

Research Requirement/Challenge	6CCVD Solution & Capability	Technical Advantage for Replication/Extension
Applicable Materials: High-quality Polycrystalline Diamond (PCD) films with controlled texture.	Polycrystalline Diamond (PCD) Wafers: We provide high-purity, inch-size PCD plates up to 125 mm diameter.	Our PCD offers superior thermal conductivity and mechanical robustness, ideal for scaling up textured films for industrial applications.
Orientation Control: Need for reproducible (100) textured PCD films achieved at high angular frequency (150 $\pi$ rad/s).	Custom Texture Engineering: 6CCVD offers PCD films with engineered preferential orientations (e.g., (100), (111)) tailored to specific electronic or mechanical requirements.	We utilize advanced MPCVD parameter control to achieve highly reproducible texture, often surpassing the control limits of HFCVD.
Large-Area Uniformity Failure: The study failed to achieve uniform deposition on 15 mm x 15 mm substrates due to a massive 200 K substrate temperature gradient.	Large-Area Uniformity & Thermal Management: 6CCVD specializes in producing PCD wafers up to 125 mm with exceptional thickness and quality uniformity (Ra < 5 nm).	Our MPCVD systems inherently provide superior thermal stability and plasma uniformity, eliminating the severe temperature gradients that limited the HFCVD/DMF study.
Thickness Requirements: Thin films (µm scale) were studied.	Broad Thickness Range: We offer SCD and PCD films from 0.1 µm up to 500 µm, and custom substrates up to 10 mm thick.	Supports both thin-film device integration (e.g., field emission) and bulk material applications (e.g., thermal spreaders).
Metalization Needs: Use of W/Mo electrodes and potential need for contacts on the diamond film.	Custom Metalization Services: We offer in-house deposition of standard and custom metal stacks, including Ti, W, Au, Pt, Pd, and Cu.	Enables direct integration of the synthesized diamond films into functional devices, such as the field emission electrodes referenced in the paper.
Engineering Support: Need for optimization of growth parameters (T, P, gas flow) for new reactor configurations (e.g., MPCVD + DMF).	In-House PhD Engineering Team: Our experts provide consultation on material selection, process optimization, and custom reactor integration for novel CVD enhancement techniques.	Accelerate R&D cycles by leveraging decades of experience in high-quality, high-rate diamond synthesis.

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

View Original Abstract

A dynamic magnetic field (DMF) with different angular frequencies (50, 100, and 150 π rad/s) was introduced during diamond growth via hot filament chemical vapor deposition (HFCVD). The effects of the dynamic magnetic field on the growth rate, diamond quality, growth orientation, and deposition uniformity of large-area diamond films were investigated with scanning electron microscopy (SEM), X-ray diffractometry (XRD), and Raman spectroscopy. The correlation between diamond growth and angular frequency was discussed. The results showed that a faster growth rate (about 2.5 times) and higher diamond quality were obtained by increasing the angular frequency of the DMF. A (100) textured polycrystalline diamond film was achieved, and the preferential orientation was found to evolve from (110) to (100), while the expected uniform deposition of a large-area diamond film under DMF was not achieved. The enhancement effect of the DMF was ascribed to the activation of more gas molecules, which participated in CVD diamond growth.

Tech Support

Original Source

DOI: https://doi.org/10.3390/coatings13020441

References

2021 - The growth behavior and surface performance enhancement of diamond film deposited on polycrystalline diamond compact [Crossref]
2003 - Preparation of diamond nanocrystals from catalysed carbon black in a high magnetic field [Crossref]
2004 - Magnetization for lower temperature, selective diamond and carbon nanotube formation: A milestone in carbon physicochemical condensation [Crossref]
2005 - Nano-Diamond Synthesis in Strong Magnetic Field [Crossref]
2009 - Influence of periodic magnetic field on the growth of CVD diamond films at lower temperature [Crossref]
2015 - Diamond film deposited on Mo-Re alloy by hot filament chemical vapor deposition with periodic magnetic field [Crossref]
2012 - Characterization of diamond films deposited on Re substrate by magnetic field-assisted hot filament chemical vapor deposition [Crossref]