Oxygen adsorption on small Si clusters: a full-potential linear-muffin-tin-orbital molecular-dynamics study

Using the full-potential linear-muffin-tin-orbital method, we have performed molecular-dynamics simulations for oxygen adsorption on Sin (n=1-7) clusters. It is found that Si1, Si2 and Si3 can react with the O2 molecule directly to form small SiO2, Si2O2 and Si3O2 molecules. For the Si clusters with more than four Si atoms, the O2 molecule cannot be adsorbed on them directly, due to the potential barrier for dissociative chemisorption of O2. In contrast, atomic oxygen favours reactions with all the silicon clusters considered here. The formation of strong Si-O bonds makes the structures of the small Si clusters obviously distorted and their stabilities decreased. As for the fragmentation, the processes from SinO2 to Sin-2 + 2SiO are found to be energetically favourable. The theoretical investigations can help us to understand the existing experimental results. (author)