Atomistic evolution of Si1–x–yGexCy thin films on Si(001) surfaces

The initial growth process of Si1−x−yGexCy thin films on Si(001) surfaces is examined by scanning tunneling microscopy. The surface morphology of the film critically depends on the C fraction in the film. Evidence is presented on an atomic scale that the epitaxial growth of Si1−x−yGexCy films with large C fractions is dominated by phase separation between Si–C and Si–Ge, concomitant with C condensation on the surface of the growing films. We find that the addition of a thin (1–2 ML) SiGe interlayer between the Si1−x−yGexCy film and the Si substrate drastically improves the film structure, leading to a planar morphology even with large C fractions present in the film.