Multiple scattering calculations of step contrast in REM images of the Si(001) surface

Simulations of reflection electron microscopy (REM) images of both monolayer and bilayer steps on the bulk-terminated Si(001) surface, for the case when the primary electron beam azimuth is directed parallel to the line of the step, are presented. The simulations employ our previously reported theory of REM image formation which uses a 2D Bloch wave formulation of dynamical (multiple scattering) elastic RHEED theory to calculate diffracted amplitudes propagating from the surface. The only step contrast mechanism considered here is phase contrast and this is sufficient to produce the characteristic “black-white” appearance observed experimentally. Defocusing of the simulated images is also discussed.