Reflection high-energy electron diffraction intensity oscillation during layer-by-layer oxidation of Si(001) surfaces

We have studied initial layer-by-layer oxidation of Si(001)-2×1 surfaces by using reflection high-energy electron diffraction (RHEED). We observed an intensity oscillation and a change in the streaky profile of a specular reflection spot in RHEED patterns during initial oxidation. These results indicate that layer-by-layer oxidation of Si surfaces is promoted by nucleation and lateral growth of two-dimensional oxide islands. We have also confirmed that a 1-monolayer-thick oxide has an ordered structure originating from the initial 2×1 reconstruction.