DETERMINATION OF SURFACE STEP DISTRIBUTIONS ON GE USING RHEED

The overwhelming feature of reflection high-energy electron diffraction (RHEED) is its extreme sensitivity to atomic steps at a surface. These steps dominate the characteristic shape of the diffracted beams and in epitaxy contribute to the time dependence of the diffracted intensity. We distinguish between two types of stepped surfaces: low-index surfaces and vicinal surfaces. A low-index surface consists of islands and islands on top of islands on top of an otherwise featureless plane. The distribution of islands on each level can be different. A vicinal surface is a surface which has been cut slightly off a low-index plane and consists of a staircase of terraces. It is easiest to treat the case where the distribution of islands on each level is identical. The diffraction from a low-index surface characteristically has a central spike due to the long-range order and a broad component due to the step disorder. The relative magnitude of these two components depends primarily on the glancing angle of incidence. A vicinal surface gives split diffracted beams, which depend more on azimuthal angle of incidence.