Morphology Transition and Layer-by-Layer Growth of Rh(111)

We have observed a morphological transition in the nucleation and growth of epitaxial Rh(111). The transition occurs near 600 K and is signaled by a change in the shape of the surface features from fingered to compact. The transition appears to be related to a change in the critical nucleation size. On both sides of the transition, there lies a regime of persistent layer-by-layer growth. The general surface features exhibit well-defined length scales and as growth proceeds they increase in size following a power-law dependence on film thickness with a morphology-independent exponent of $0.33\pm 0.03$. The results suggest a general pathway to the layer-by-layer growth of close-packed metals.