CONDUCTANCE OF AG ON SI (111) - A 2-DIMENSIONAL PERCOLATION PROBLEM

It is well known that silver grows epitaxially on Si (111)-7 x 7. We d eposited several monolayers of silver on silicon under UHV conditions (p = 1 x 10(-10) mbar). Due to the perfect substrate we were able to o bserve electric conduction of one monolayer of silver. We made in situ measurements of the conductance during growth in the temperature rang e 50-130 K. We show that conduction starts at a critical coverage less than a monolayer, and the critical coverage decreases for increasing deposition temperature. We discuss a percolation model and several pos sible growth modes.