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

Abstract

High-energy ion scattering and channeling and low-energy electron diffraction are used to investigate quantitatively the initial stages of interface formation (overlayer thickness up to ∼10 Å) 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)-2×1 substrate but not the Si(111)-7×7. This difference is discussed in terms of structural models for these surfaces. On both surfaces, however, deposition at 300 K results in a highly imperfect overlayer. To obtain high-quality growth, a deposition temperature of ∼790 K is needed for Si(111)-7×7 and of ∼570 K for Si(100)-2×1. The implications of these results with respect to molecular-beam epitaxy are discussed.