IN-SITU ATOMIC-FORCE MICROSCOPY OF THE ELECTROCHEMICAL DISSOLUTION OFA COPPER GRAIN

Dynamic evolution of the submicrometer surface morphology of a copper grain undergoing electrodissolution in the ''electroetching regime'' h as been monitored by in situ atomic force microscopy. Images obtained for a nominal current density of 400 mu A cm(-2) indicate rapid etchin g into the surface to reveal well-defined crystallographic faces. The thermodynamically most stable {111} facets develop first, forming the initial primary dissolution faces; but as dissolution progresses, they are replaced by stably dissolving {211} and {221} facets. Hence, surf ace morphology can either be thermodynamically or kinetically controll ed. Local current density is distributed inhomogeneously at the submic rometer level, being 1 order of magnitude larger than the global avera ge at some locations. Identical crystallographic facets do not etch at the same rate and the dissolving facets typically evolve in a complex temporal-spatial manner. This behavior may be related to nonlinear pa ttern formation. Images obtained for a lower current density of 20 mu A cm(-2) provide unequivocal evidence of a surface recrystallization p henomenon concurrent with the anodic dissolution process. The surface reordering extends up to the submicrometer length scale and leads to d evelopment of smooth facets.