(141h) Synthesis of SiC Thin Films Via Plasma Enhanced Chemical Vapor Deposition (PECVD) Combined with in-Situ Pyrolysis

SiC inorganic materials have received attention due to their superior chemical, thermal, and mechanical stability, which allows their use in various applications where their resilience to harsh operating conditions is important [1]. SiC nanoporous membranes are a class of such materials which find use today in separation applications requiring high durability and efficiency, like those involved during hydrogen (H₂) production [2]. The fabrication of SiC membranes presents significant challenges, however, due to the need to use toxic solvents and employ complex processing schemes [3]. In this study, we use plasma-enhanced chemical vapor deposition (PECVD) to deposit organosilicon pre-ceramic polymer films on macroporous SiC substrates, followed by in-situ pyrolysis to synthesize robust, thin asymmetric nanoporous SiC ceramic membranes. The PECVD technique allows for precise control of the thickness of the deposited film, and its low processing temperature reduces thermal stresses during film formation, thus preventing crack generation. We also employ in-situ pyrolysis to avoid exposing the pre-ceramic polymer films to ambient air to reduce oxygen contamination. In-situ pyrolysis enables, in addition, multiple (deposition + pyrolysis) cycles without the need to pump-down the PECVD chamber, which is advantageous for minimizing processing time and the energy required. We have found that the optimum temperature to convert SiC polymer precursors into ceramics is ~800 °C, with most of the mass loss during the pyrolysis process occurring between 350 °C and 520 °C. Elemental analysis, including EDS, XPS, FT-IR, and Raman, confirms the successful synthesis of SiC films.

References:

1. Wang, Y., et al., Recent progress in the pore size control of silicon carbide ceramic membranes. Ceramics International, 2022. 48(7): p. 8960-8971.
2. Nguyen, B., et al., Fabrication of SiC-Type Films Using Low-Energy Plasma-Enhanced Chemical Vapor Deposition (PECVD) and Subsequent Pyrolysis. Industrial & Engineering Chemistry Research, 2023. 62(24): p. 9474-9491.
3. He, R., et al., Progress and challenges towards additive manufacturing of SiC ceramic. Journal of Advanced Ceramics, 2021. 10: p. 637-674.