Crystal facet dependence of SiHCl3 reduction to Si mechanism on silicon rod

[Display omitted] •SiHCl3 decomposition to Si is mainly formed on Si(111) facet due to the highest atomic density and the stronger Si-Si bond.•SiHCl3 decomposition to SiCl4 is more favorable than Si formation in gas phase reaction.•Promoting SiHCl3 decomposition to Si through exposing more (111) surface area and optimizing the flow field and temperature distribution in the reactor. Clarifying the mechanism of SiHCl3 decomposition on silicon rod and in gas phase has a remarkable impact on intensifying the technology of polycrystalline silicon production from SiHCl3. Our work investigates the mechanism of SiHCl3 decomposition on low index plane of silicon crystal—(111), (110) and (100) by density functional theory (DFT), and further explores the mechanism in gas phase. SiHCl3 decomposition to Si is mainly formed on Si(111) facet due to the highest atomic density and the stronger Si-Si bond; the most favorable path is SiHCl3 → SiCl3 + H → SiCl2 + Cl → SiCl + Cl → Si + Cl. The three coordination Si atoms on Si(110) and Si(100) are not in the same plane; Si(110) and Si(100) are not beneficial to SiHCl3 decomposition to Si. In gas phase reaction, SiHCl3 decomposition to SiCl4 is more favorable than Si formation. In kinetics, when the temperature of silicon rod is higher than that in gas phase, the formation of Si has more advantages than SiCl4. The findings enhance our understandings about the crystal facet structure-dependent performances of silicon crystal in polycrystalline silicon production, and provide a useful guidance for promoting SiHCl3 decomposition to Si through exposing more (111) surface area of silicon rod and optimizing the flow field and temperature distribution in the reactor.