Adsorption Behaviors of Chlorosilanes, HCl, and H₂ on the Si(100) Surface: A First-Principles Study

The hydrochlorination process is a necessary technological step for the production of polycrystalline silicon using the Siemens method. In this work, the adsorption behaviors of silicon tetrachloride (SiCl₄), silicon dichloride (SiCl₂), dichlorosilane (SiH₂Cl₂), trichlorosilane (SiHCl₃), HCl, and H₂ on the Si(100) surface were investigated by first-principles calculations. The different adsorption sites and adsorption orientations were taken into account. The adsorption energy, charge transfer, and electronic properties of different adsorption systems were systematically analyzed. The results show that all of the molecules undergo dissociative chemisorption at appropriate adsorption sites, and SiHCl₃ has the largest adsorption strength. The analysis of charge transfer indicates that all of the adsorbed molecules behave as electron acceptors. Furthermore, strong interactions can be found between gas molecules and the Si(100) surface as proved by the analysis of electronic properties. In addition, SiCl₂ can be formed by the dissociation of SiCl₄, SiH₂Cl₂, and SiHCl₃. The transformation process from SiCl₄ to SiCl₂ is exothermic without any energy barrier. While SiH₂Cl₂ and SiHCl₃ can be spontaneously dissociated into SiHCl₂, SiHCl₂ should overcome about 110 kJ/mol energy barrier to form SiCl₂. Our works can provide theoretical guidance for hydrochlorination of SiCl₄ in the experimental method.