When Ag adatoms were deposited on top of the Si(111)-√3×√3-Ag surface at room temperature with less than a critical coverage ${\mathrm{\Theta }}_{\mathit{C}}$ (∼0.03 atomic layer), they were found to exist as a supersaturated metastable two-dimensional gas phase, which made the surface electrical conductance extremely high. With the coverage beyond ${\mathrm{\Theta }}_{\mathit{C}}$, the gas phase began to nucleate into three-dimensional microcrystals, leading to a steep reduction in the electrical conductance. A kinetic overshoot beyond the critical supersaturation for nucleation was also detected in in situ conductance measurements during the Ag deposition. © 1996 The American Physical Society.

• Received 19 July 1996

DOI:https://doi.org/10.1103/PhysRevB.54.14134