Abstract: Coating the surface of goethite nanoparticles by Si, Co oxides layer is one of the most important methods to improve the magnetic properties of metal magnetic
recording particles. The surface electronic properties of the coated nanoparticles were studied by using XPS. Results show that there is a close, uniform, firm and
ultra thin SiO₂ layer formed on the surface of hematite nanoparticles. Silica coating treatment changes the properties of the hematite cores significantly since
the binding energy of Fe 2p electrons shows significant shift related to the spectrum of the untreated hematite particles. The chemical shift of the binding
energy is more than 2.7eV. A possible interpretation for the shift of such spectral features is that the contact interface surface of silica layer and the hematite
particle surface is similar to P-N heterojunction. The cobalt oxides are adsorbed on part of the crystal face of Fe₂O₃ particles, and the binding energy of
whole XPS spectrum mainly shows physical shift about 4.4eV due to the surface charge.

Key words: coated nanoparticles, XPS, heterojunction