Mechanism of oxidation protection of the Si(001) surface by sub-monolayer Sr template

We investigate theoretically the oxidation stability of the Si(001) (2 x 1) reconstructed surface passivated by Sr. Using density functional theory, we find that the Sr surface with 1/2 monolayer of Sr is protected against oxidation. The presence of Sr delays the oxidation of the surface dimer, and even when the dimer is oxidized, O does not react with the back-bond, preventing the unwanted vertical growth of SiO2. We also show that 1/4 monolayer of Sr protects the Si surface in a different way. In the presence of 1/4 monolayer of Sr, O atoms are attracted to the Sr-Si dimer complexes, thus preventing the formation of SiO2. Published by AIP Publishing.