  Magnetite (Fe3O4) thin films on GaAs have been studied with HArd X-ray
PhotoElectron Spectroscopy (HAXPES) and low-energy electron diffraction. Films
prepared under different growth conditions are compared with respect to
stoichiometry, oxidation, and chemical nature. Employing the considerably
enhanced probing depth of HAXPES as compared to conventional x-ray
photoelectron spectroscopy (XPS) allows us to investigate the chemical state of
the film-substrate interfaces. The degree of oxidation and intermixing at the
interface are dependent on the applied growth conditions; in particular, we
found that metallic Fe, As2O3, and Ga2O3 exist at the interface. These
interface phases might be detrimental for spin injection from magnetite into
GaAs.
