Dissociation Pathways for ClCN on Si(100)-(2 × 1) Modeled by Multiple Si-Dimer Clusters

Abstract

Electronic structure calculations for ClCN adsorbed multiple Si-dimer clusters are performed to investigate dissociation pathways for ClCN into adsorbed atomic Cl and molecular CN. Reaction pathways across adjacent Si-dimers are modeled using double-dimer (Si15H16) and triple-dimer (Si21H20) clusters. Clusters created by combining two single-dimer (Si23H24), double-dimer (Si39H32), or triple-dimer (Si55H40) clusters in an end-to-end fashion are utilized to investigate pathways across two Si-dimer rows. These computations show that the key step in the decomposition of ClCN on the Si(100) surface is the dissociation of the CCl bond. The CCl bond dissociation across two Si-dimers either in the same row or in different rows is significantly lower than that found for dissociation across a single Si-dimer. The use of multiple-dimer reaction pathways is required to provide a realistic model for ClCN dissociation on the Si(100) surface. These computations provide an explanation for the experimental observation of only the adsorbed ClCN species and final adsorbed atomic Cl and molecular CN species on the Si(100) surface.