Nucleation and growth of Fe and FeO nanoparticles and films on Au(1 1 1)

We have studied the formation of Fe and FeO nanoparticles and thin films on the reconstructed Au(1 1 1) surface. Scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and ion-scattering spectroscopy (ISS) were used to evaluate the structure and composition of Fe and FeO nanoparticles and films at different growth conditions. Iron grows as one monolayer high triangular particles on the Au(1 1 1) reconstruction. FeO was grown by exposing the Fe nanoparticles to molecular oxygen at 323 K, followed by annealing at 500-700 K. XPS results indicate that FeO is formed after room temperature oxidation. STM images show that well-ordered iron oxide particles form after annealing to 700 K. STM images also show evidence of a overlayer lattice with a short periodicity of 3.3 Å modulated by a larger periodicity of approximately 35 Å. The larger periodicity results from a moiré pattern formed between the iron oxide overlayer and the underlying Au(1 1 1) surface.