  Scanning Tunneling Microscopy (STM) has been used to study the morphology of
Ag, Pb and Pb/Ag bilayer films fabricated by quench condensation of the
elements onto cold (T=77K), inert and atomically flat Highly Oriented Pyrolytic
Graphite (HOPG) substrates. All films are thinner than 10 nm and show a
granular structure that is consistent with earlier studies of QC films. The
average lateral diameter, $\bar {2r}$, of the Ag grains, however, depends on
whether the Ag is deposited directly on HOPG ($\bar {2r}$ = 13 nm) or on a Pb
film consisting of a single layer of Pb grains ($\bar {2r}$ = 26.8 nm). In
addition, the critical thickness for electrical conduction ($d_{G}$) of Pb/Ag
films on inert glass substrates is substantially larger than for pure Ag films.
These results are evidence that the structure of the underlying substrate
exerts an influence on the size of the grains in QC films. We propose a
qualitative explanation for this previously unencountered phenomenon.
