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 deposited several monolayers of silver on silicon under UHV conditions (p = 1 x 10(-10) mbar). Due to the perfect substrate we were able to observe electric conduction of one monolayer of silver. We made in situ measurements of the conductance during growth in the temperature range 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 possible growth modes.