Key Takeaways & Executive Findings
- •• SiC reinforced pyrolytic graphite (PyG) coating significantly enhances corrosion resistance in SiC vapor environments at ultra-high temperatures (2050°C for 120 h). • The addition of SiC particles improves the graphitization degree and structural stability of PyG coatings, leading to a more intact protective layer. • Raman spectroscopy analysis shows a 17.2% reduction in ID/IG ratio for SiC-reinforced PyG coating, compared to 6.5% for plain PyG, indicating superior corrosion resistance. • This work provides a theoretical foundation for using SiC-reinforced PyG coatings to protect graphite components in SiC single crystal growth via PVT method.
Abstract
In order to effectively prevent the contamination of carbon particle volatiles during high-purity SiC crystals are prepared using the physical vapor transport (PVT) method in ultra-high temperature environments (T≥2000 ℃), this study innovatively attempts to protect graphite materials with SiC reinforced pyrolytic graphite (PyG) coating. It is discovered by preparing the SiC particle layer, the degree of graphitization and stability of PyG coating can be improved. The corrosion test results demonstrated that the SiC reinforced PyG coating can maintain an intact coating with a high graphitization degree after the SiC vapour corrosion test of 2050 ℃-120 h. Conversely, the samples with and without PyG coating reveal porous and eroded surfaces. Furthermore, following the SiC vapour corrosion test, the PyG coating sample’s integral ratio of D-band and G-band (ID/IG) of Raman spectrum test data, reduced by 6.5%, while the SiC reinforced PyG coating decreased by 17.2%, indicating its excellent corrosion resistance. The application of SiC reinforced pyrolytic graphite coating in preparing the SiC single crystal might received a theoretical foundation according to this work.
1. Introduction
Silicon carbide (SiC) is the core material of the third-generation wide band gap semiconductor, and the manufacture of SiC power semiconductor devices is based on the huge size and high quality of SiC single crystal wafers [1−4]. At present, the primary methods for crystal growth are physical vapour transport (PVT), high-temperature chemical vapour deposition (HT-CVD), and liquid phase epitaxy (LPE). The PVT method, which has the highest technical maturity and the most widely used in engineering, is the mainstream commercial method for the growth of SiC wafers. SiC will decompose and sublimate into a variety of vapour components, including Si, Si2C, and SiC2, when treated by the PVT method at a high temperature above 1800 ℃. When transported to a lower temperature zone, these components will react and recrystallize to form solid phase SiC. The heater used in the growth of silicon carbide crystal is graphite crucible, which will be eroded by SiC mixture vapour and crucially reduce the service life of graphite [5]. The coating might provide a protective barrier for the graphite material, ensure its safety and reliability under the action of harsh environmental media, and extend its service life. By applying pyrolytic graphite (PyG) coating to graphite materials in the SiC single crystal growth environment, this study have attempted to get around the materials’ limitations.
Pyrolytic graphite is produced by the pyrolytic deposition of hydrocarbon sources by chemical vapour deposition above 1800 ℃ [6]. PyG is a highly pure and oriented unique form of synthetic graphite with a highly preferred orientation of graphitic planes parallel to the substrate surface [7]. The PyG pyrolyzed above 2100 ℃ is characterized by with near theoretical density (2.2 g/cm3), the structure is dense and nearly non-porous, has very low gas permeability, good chemical stability at high temperatures, and has good thermal shock resistance and high erosion resistance, and is commonly used as a coating for high-temperature devices [8−11].
However, the preparation of pyrolytic graphite coating has very high requirements for equipment, which makes it difficult to meet the requirements of high-temperature service environment [12−18]. The crystallization and corrosion resistance of pyrolytic graphite prepared at lower temperatures is poor, Therefore, in order to improve the performance of the pyrolytic graphite coating prepared at a lower temperature, it is necessary to find ways to improve the crystallinity of the pyrolytic graphite coating. It has been discovered that the addition of some metal elements, carbides, or oxide additives to the carbon matrix can influence the graphitization during the heat treatment process of carbon materials and improve the microstructure of the materials [19].
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TAO Xian-cheng, SUN Wei, SUN Ye-hua, DENG Nan-jun, WANG Zi-wei, XIONG Xiang (2026). Microstructure and the corrosion resistance of SiC reinforced pyrolytic graphite coating under physical vapor transport SiC environment. Journal of Central South University. https://doi.org/10.1007/s11771-026-6166-9
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Frequently Asked Questions
What is the main purpose of the SiC reinforced pyrolytic graphite coating?
The coating is designed to protect graphite materials from corrosion by SiC vapor during the physical vapor transport (PVT) growth of SiC single crystals at ultra-high temperatures, thereby extending the service life of graphite components.
How does the SiC reinforcement improve the pyrolytic graphite coating?
The addition of SiC particles enhances the degree of graphitization and structural stability of the pyrolytic graphite coating, leading to improved corrosion resistance and integrity under harsh SiC vapor environments.
What were the key results of the corrosion tests?
After exposure to SiC vapor at 2050°C for 120 hours, the SiC reinforced PyG coating remained intact with high graphitization, while samples without the coating or with plain PyG showed porous and eroded surfaces. Raman analysis showed a 17.2% decrease in ID/IG ratio for the reinforced coating, indicating superior corrosion resistance.
What is the significance of this research for SiC crystal growth?
This work provides a theoretical foundation for using SiC reinforced pyrolytic graphite coatings to protect graphite crucibles and heaters in PVT SiC growth, potentially improving the quality and yield of SiC single crystals by reducing contamination and equipment degradation.
What methods were used to evaluate the coating performance?
The performance was evaluated through corrosion tests at 2050°C for 120 hours, followed by microstructural analysis and Raman spectroscopy to measure the ID/IG ratio, which indicates the degree of graphitization and corrosion resistance.
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