  We address the question of the spatial resolution of ballistic electron
emission microscopy (BEEM) of Shottky barriers in Au(111)/Si(100) and
Au(111)/Si(111) interfaces. A novel combination of Green-function and k-space
Ensemble-Monte-Carlo techniques is used to obtain new insights into the spatial
and energetic evolution of the STM-tip-induced electrons during their passage
through the metallic layer before reaching the metal-semiconductor interface.
In particular, it is shown how the effect of band-structure-induced directional
focusing of the electrons enforces a reinterpretation of existing experimental
data.
