Atomic force microscopy study of surface evolution during electrocrystallization of zinc-iron alloys

Zn-Fe alloys, composed of eta (h.c.p.) phase, were electrolytically deposited on cold rolled steel substrates from sulfate electrolytes. Deposits, which initially exhibited a morphology of approximately 20 nm thick platelets inclined 10-20 deg to the substrate surface, subsequently evolved either into triangular pyramids or hexagonal columnar crystals depending on the deposition conditions. A combination of X-ray texture measurements and AFM topographical analysis was used to characterize the growth surface of Zn-Fe alloys. For the morphology of hexagonal columnar crystals, the (00.1) basal planes were aligned perpendicular to the growth direction. For the morphology of the triangular pyramids, the (10.0) and (00.1) planes of eta phase were tilted to the growth direction and surrounded the growth surface. For both morphologies the micro-and nanosize steps of growth were identified.