Initial stages of silicon molecular beam epitaxy: Effects of surface reconstruction.

High energy ion scattering/channeling and low energy electron diffraction is used to investigate quantitatively the initial stages of interface formation (overlayer thickness up to ~10angstroms) during Si molecular beam epitaxy. Changes in the geometry of the Si substrate surface, i.e. reordering, and of the Si overlayer are measured as a function of Si coverage, deposition temperature and substrate reconstruction. It is found that room-temperature deposition reorders the Si(100)-2x1 substrate but not the Si (111)-7x7. This difference is discussed in terms of structural models for these surfaces. On both surfaces, however, deposition at 300K results in a highly imperfect overlayer.