If a metallic overlayer is very thin, its surface electronic structure
will be different from that of a thick slab of the same metal. Notabl
y, surface band gaps and certain surface states need a minimum thickne
ss of the crystal structure underneath to be fully developed. If the o
verlayer thickness is less than that, then the surface electronic prop
erties will be thickness-dependent. A metallic overlayer which is atom
ically flat on the surface, but which covers a step in the interface,
will have different electronic structures on the two sides of the step
. This paper investigates if, and under what conditions, such a behavi
our can be picked up by a scanning tunneling microscope (STM). This is
done by calculating STM data for Ag/Pd(111), Ag/Pd(100), and Cu/Ni(10
0). The results show tip height changes in the order of 0.1 angstrom f
or layer thicknesses of up to four monolayers.