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), dichlorosi-lane (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.