Generation of clean iron nanocrystals on an ultra-thin SiOx film on Si(001)

Abstract

Upon exposure to Fe(CO)₅, the formation of pure cubic Fe nanocrystals with dimensions up to ∼75 nm is reported on ultra-thin SiO_x films (thickness ≈ 0.5 nm) on Si(001), which have been prepared in situ under UHV conditions. The active centers for initial decomposition of Fe(CO)₅ resulting in the growth of the Fe clusters are proposed to be SiO sites. After nucleation at these sites, further crystal growth is observed due to autocatalytic dissociation of Fe(CO)₅ at room temperature. The density of the Fe clusters can be increased by irradiating the surface with a focused electron beam (15 keV) prior to gas exposure. The formation of the active SiO sites upon electron irradiation is attributed to oxygen desorption via the Knotek–Feibelman mechanism.