Synthesis of Polycrystalline Diamond Films in Microwave Plasma at Ultrahigh Concentrations of Methane

Polycrystalline diamond (PCD) films are usually grown by chemical vapor deposition (CVD) in hydrogen–methane mixtures. The synthesis conditions determine the structure and quality of the grown material. Here, we report the complex effect of the microwave plasma CVD conditions on the morphology, grow...

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Bibliographic Details
Published in:Coatings (Basel) 2023-04, Vol.13 (4), p.751
Main Authors: Martyanov, Artem, Tiazhelov, Ivan, Savin, Sergey, Voronov, Valery, Konov, Vitaly, Sedov, Vadim
Format: Article
Language:English
Subjects:
Analysis
Chemical vapor deposition
Cutting tools
Diamond films
Gas flow
Hardness
Heat conductivity
Lasers
Methane
Methods
Microwave plasmas
Morphology
Phase composition
Plasma
Polycrystalline diamond
Polycrystals
Production processes
Properties
Raman spectroscopy
Silicon wafers
Spectrum analysis
Structure
Substrates
Synthesis
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Summary:Polycrystalline diamond (PCD) films are usually grown by chemical vapor deposition (CVD) in hydrogen–methane mixtures. The synthesis conditions determine the structure and quality of the grown material. Here, we report the complex effect of the microwave plasma CVD conditions on the morphology, growth rate and phase composition of the resulting PCD films. Specifically, we focus on the factors of (i) increased methane concentrations (νc) that are varied over a wide range of 4%–100% (i.e., pure methane gas) and (ii) substrate temperatures (Ts) varied between 700–1050 °C. Using scanning electron microscopy, X-ray diffraction and Raman spectroscopy, we show that diamond growth is possible even at ultrahigh methane concentrations, including νc = 100%, which requires relatively low synthesis temperatures of Ts < 800 °C. In general, lower substrate temperatures tend to facilitate the formation of higher-quality PCD films; however, this comes at the cost of lower growth rates. The growth rate of PCD coatings has a non-linear trend: for samples grown at Ts = 800 °C, the growth rate increases from 0.6 µm/h at νc = 4% to 3.4 µm/h at νc = 20% and then falls to 0.6 µm/h at νc = 100%. This research is a step toward control over the nature of the CVD-grown PCD material, which is essential for the precise and flexible production of diamond for various applications.
ISSN:2079-6412
2079-6412
DOI:10.3390/coatings13040751