Surfactant properties of chemisorbed oxygen in Fe/Fe(001) homoepitaxy: a He diffraction study

He diffraction measurements show that preadsorption of an O(1×1) phase on Fe(001) promotes two-dimensional growth of Fe at temperatures below 400 K, in contrast to the island growth observed on the bare Fe(001) surface. Oxygen floats at the surface, acting as a surfactant. After repeated cycles of film annealing and Fe re-deposition, a beat is observed in the pattern of He reflectivity measured as a function of deposition time. The beat is assigned to the growth on surface domains characterized by a different surfactant efficiency.