Paper SS1-WeM3
Destabilization of Ag Nanoislands on Ag(100) by Adsorbed Sulfur

Wednesday, November 2, 2011, 8:40 am, Room 107

Studies of chalcogen (O, S) interactions with coinage metal surfaces elucidate how those interactions affect mass transport on the surface and whether a general mechanism exists for these systems. Sulfur accelerates coarsening of Ag nanoislands on Ag(100) at 300 K, and this effect increases with sulfur coverage over a range spanning a few hundredths of a monolayer, to nearly 0.25 monolayers. We propose that acceleration in this system is strongly tied to the formation of AgS₂ complexes at step edges. These complexes can transport Ag more efficiently than Ag adatoms (due to a lower diffusion barrier and comparable formation energy), hence leading to enhanced coarsening. The mobility of isolated sulfur on Ag(100) is very low, so that complex formation is kinetically-limited at low sulfur coverages, and thus enhancement is minimal. However, higher sulfur coverages force the population of sites adjacent to step edges, so that formation of the complex is no longer limited by diffusion of sulfur.