Theoretical study of Si–Ge mixed dimers on Si(001) surfaces

Abstract

We have studied the atomic geometry of mixed Si–Ge dimers on Si(001) surface, using first-principle total energy calculations. Our results indicate that the formation of mixed Si–Ge dimers, with the Si atoms in a “down” position and the Ge atoms in an “up” position, is an energetically more favourable surface topology with respect to the switching between Si and Ge atoms, where the Si atoms occupy an “up” position and the Ge atoms occupy a “down” position. The formation of pure Si–Si and Ge–Ge buckled dimers was also considered, and our results indicate that this structure is not energetically favourable against formation of mixed Si–Ge buckled dimers. For a 2×4 surface covered by mixed Si–Ge buckled dimers in an antiphase topology, our total energy calculations indicate that this configuration is energetically equivalent to the 2×4 surface in a semi-antiphase topology.