Preparation and characterization of Fe 3O 4(1 1 1) nanoparticles and thin films on Au(1 1 1)

Abstract

Fe 3O 4 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). Fe 3O 4 was formed by annealing α-Fe 2O 3(0 0 0 1) structures on Au(1 1 1) at 750 K in ultrahigh vacuum (UHV) for 60 min. Transformation of the α-Fe 2O 3(0 0 0 1) structures into Fe 3O 4 nanoparticles and thin films was supported by XPS. STM images show that during the growth procedure used, Fe 3O 4 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 Fe 3O 4 particles with periodicities of ∼50 and ∼42 Å, respectively. As the Fe 3O 4 particles form more continuous films, the ∼50 Å feature was the predominant superstructure observed. The Fe 3O 4 structures at all coverages show a hexagonal unit cell with a ∼3 Å periodicity in the atomically resolved STM images.