Dynamics of reactions inhibiting epitaxial growth of Si(100) surfaces via interaction with hydrogen chloride

The dynamics of reactions of HCl at growing Si(100) surfaces was investigated through computational methods, using clusters of different sizes and shapes. The analysis was conducted through Gaussian09 at the B3LYP/6-31G(d,p) level. It was found that adsorption of HCl on H-passivated dimers does not proceed as easily as on non-passivated dimers. In addition, analysis of reactions between HCl and a SiCl₂ moiety adsorbed on a surface dimer indicated that HCl can lead to detachment of the SiCl₂ moiety from the surface in the form of a SiCl₂ or a SiHCl₃ molecule, or to diffusion of the moiety to a neighboring dimer. However, when the dimer on which SiCl₂ adsorbs had been H-passivated prior to adsorption, the reaction of HCl with the SiCl₂ moiety becomes significantly more difficult. H-passivation of surface dimers seems thus to promote surface growth by protecting the surface against HCl adsorption and by preventing detachment or diffusion of the adsorbed SiCl₂ moiety, which is pointed out as an important intermediate in the growth mechanism. These results are in consonance with evidence found for the convenience of H-passivation of surface dimers prior to silicon deposition, already published in the literature.