Electronic structure of granular Fe–Al2O3 thin films prepared by co-evaporation

We studied the electronic structure of granular Fe–Al2O3 thin films using X-ray photoelectron spectroscopy (XPS). The samples were produced by co-evaporation of Fe and Al2O3 and have relatively large Fe volume factions (27 and 48%). The Fe 2p XPS spectra show that the Fe precipitates in the granular alloy are in a majority metallic phase. The spectra show also that there is a minority Fe oxide phase and that this phase decreases for the 48% sample. The valence band spectra of granular Fe–Al2O3 can be understood as a linear combination of the individual Fe and Al2O3 bands, which is consistent with mostly metallic Fe precipitates deduced from the core level Fe 2p XPS spectra. The core level and valence band results suggest the possibility of little interaction between the Fe precipitates and the Al2O3 matrix. In turn, this would suggest that there is little interdiffusion as well as relatively well-defined and abrupt grain boundaries. This information is important to understand the transport and magnetic properties of the Fe–Al2O3 thin films.