Preparation and characterization of Fe3O4(1 1 1) nanoparticles and thin films on Au(1 1 1)

Fe3O4 nanoparticles and thin films were prepared on the Au(1 1 1) surface and characterized using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). Fe3O4 was formed by annealing α-Fe2O3(0 0 0 1) structures on Au(1 1 1) at 750 K in ultrahigh vacuum (UHV) for 60 min. Transformation of the α-Fe2O3(0 0 0 1) structures into Fe3O4 nanoparticles and thin films was supported by XPS. STM images show that during the growth procedure used, Fe3O4 initially appears as nanoparticles at low coverages, and forms thin films at ∼2 monolayer equivalents (MLE) of iron. Two types of ordered superstructures were observed on the Fe3O4 particles with periodicities of ∼50 and ∼42 Å, respectively. As the Fe3O4 particles form more continuous films, the ∼50 Å feature was the predominant superstructure observed. The Fe3O4 structures at all coverages show a hexagonal unit cell with a ∼3 Å periodicity in the atomically resolved STM images.