SURFACE-REACTIONS OF AU(111) WITH AQUEOUS CYANIDE STUDIED BY SCANNING TUNNELING MICROSCOPY

Dilute solutions (10(-4)-10(-5) M) of aqueous cyanide cause the formation of monolayer pits on Au(111) as studied by scanning tunneling microscopy (STM). The roughly triangular etch pits on the (111) terraces reflect the 3-fold rotational symmetry of the fcc Au(111) crystal and appear to format atomic defects on the terrace. In situ STM of the pitted Au(111) surface in 5 x 10(-5) M KCN shows that the pits collapse in minutes due to enhanced mobility of Au atoms from adsorbed cyanide. A mobile step edge/adatom diffusion model is used to explain the nature of the pit collapse. This is the first STM study of in situ monolayer pit formation and annealing in an aqueous chemical etchant.