I n s i t u scanning tunneling microscopy of inhibited Cu and Cu–Au electrodissolution in aqueous media

Abstract

I n situ scanning tunneling microscopy (STM) of copper dissolution in the Tafel region, shows that the initial mechanically polished surface (0.05-μm Al2O3 ) roughens by forming large scale (μm) plateaus that appear to consist of low index hkl facets, while the plateaus, themselves, become smoother (<100 nm scale) than the as-prepared surface. The tendencies for both plateau development and smoothing of the plateaus are slowed by the addition of inhibitor to the solution and this inhibiting effect is particularly strong in some regions suggesting the preferential adsorption of the inhibitor on the surface. Real-time STM of the profuse surface roughening (10–102 nm scale) that occurs during selective dissolution of Cu from the Cu–Au alloy is illustrated. As in post (ex situ) STM examination, the scale of the roughness in the plane of the surface is found to be in good agreement with scanning electron microscopy results, but the depth of the roughness (pits) is severely underestimated except at the very initial stages of surface roughening.