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

Abstract

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 (SiCl 4 ), silicon dichloride (SiCl 2 ), dichlorosilane (SiH 2 Cl 2 ), trichlorosilane (SiHCl 3 ), HCl, and H 2 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 SiHCl 3 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, SiCl 2 can be formed by the dissociation of SiCl 4 , SiH 2 Cl 2 , and SiHCl 3 . The transformation process from SiCl 4 to SiCl 2 is exothermic without any energy barrier. While SiH 2 Cl 2 and SiHCl 3 can be spontaneously dissociated into SiHCl 2 , SiHCl 2 should overcome about 110 kJ/mol energy barrier to form SiCl 2 . Our works can provide theoretical guidance for hydrochlorination of SiCl 4 in the experimental method.

Bifunctional Silica-Supported Ionic Liquid Phase (SILP) Catalysts in Silane Production: Their Synthesis, Characterization and Catalytic Activity

“…The first is based on the hydrochlorination of technical silicon into trichlorosilane, followed by its separation from the vapor–gas mixture and hydrogen reduction to polysilicon [ 4 , 5 ]. The Siemens process is quite energy-intensive (the temperature of the SiHCl 3 hydrogen reduction is 1200 °C) and highly toxic; SiCl 4 (in an amount of 18 tons per 1 ton of the main product) and HCl are released as by-products [ 6 , 7 , 8 ]. In the Union Carbide process, monosilane (a precursor of polycrystalline silicon) is obtained as the result of the catalytic disproportionation of trichlorosilane (process temperature—80 °C), shown by reaction Equations (1)–(3) [ 9 ].…”

Numerical Simulation of Fluidization Behavior and Chemical Performance for Hydrochlorination of Silicon Tetrachloride in a Fluidized Bed Reactor

“…The central apparatus for SiCl 4 hydrogenation [8] is the fluidized bed reactor (FBR), and the primary chemical reaction is depicted in Equation (1). Furthermore, the hydrochlorination process [9], which represents an optimized hydrogenation technology, introduces HCl as an additional reactant. This process offers notable advantages, including high conversion rates and low energy consumption [10].…”