Preparation and Formation Mechanism of β-SiC Coatings Using a SiCl₄-CH₄-H₂-N₂ System

Area of Science:

• Materials Science
• Chemical Engineering
• Physical Chemistry

Background:

• The mechanism of beta-silicon carbide (β-SiC) preparation via chemical vapor deposition (CVD) using the SiCl₄-CH₄-H₂-N₂ system is not fully understood.
• Nitrogen's role in the CVD process for β-SiC synthesis requires clarification.

Purpose of the Study:

• To elucidate the reaction mechanism and thermodynamic principles governing β-SiC CVD.
• To determine the optimal reaction pathway and temperature for efficient β-SiC synthesis.
• To provide a theoretical and technical foundation for fabricating SiC-coated graphite trays.

Main Methods:

• Thermodynamic analysis using HSC Chemistry code to calculate Gibbs free energy changes for potential reaction pathways.
• Systematic calculation of thermodynamic equilibrium components for seven proposed CVD β-SiC reactions.
• Kinetic study of the CVD process.
• Characterization of β-SiC coatings using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy.

Main Results:

• The study identified the most viable reaction pathway and optimal temperature range for CVD β-SiC preparation.
• Nitrogen's role in the reaction mechanism was confirmed.
• Uniform, dense β-SiC coatings with fine grains and high crystallinity were successfully produced.
• Large-scale (230 and 465 mm diameter) SiC-coated graphite trays with an average β-SiC thickness of 100.6 μm were fabricated.

Conclusions:

• The research provides crucial insights into the CVD mechanism of β-SiC.
• Optimal conditions for producing high-quality β-SiC coatings were determined.
• The findings support the fabrication of SiC-coated graphite trays for metal-organic chemical vapor deposition (MOCVD) applications.