The technological importance of Schottky barriers has led to many expe
riments of metal-on-semiconductor systems. Here we present an example
of the inverse case by depositing a semiconductor on a metal, studying
the very early stages of the metal-semiconductor interface formation.
We show that 0.5 monolayers of Si on Cu(110) form an ordered c(2 X 2)
overlayer and resolve its geometrical structure. Using full-hemispher
ical x-ray photoelectron diffraction, we find that Si atoms form an al
most coplanar layer, replacing one out of two Cu surface atoms.