Characterization of Aluminum Oxide Thin Films Formed on Surfaces of FeCo-V Alloys by Annealing under a Low Partial Pressure of Oxygen

The aluminum oxide thin films formed on the surfaces of FeCo-V al-loys doped with a small amount of aluminum were characterized by ellipsometry and electrical resistivity measurements. Aluminum oxide films on alloy surfaces were selectively formed by annealing under a low partial pressure of oxygen. The thickness of the oxide films in-creased with increasing aluminum content and temperature. However, the electrical resistivity of the oxide thin films did not correlate with the thickness of the oxide films. To clarify the anomaly of the resistivity, micro-beam X-ray photoelectron spectroscopy (XPS) was used to char-acterize the two-dimensional distribution of elements on the alloy sur-face. The XPS results show that the oxide films were partially exfoliated in the alloys with a high aluminum content. In particular, the oxide films were likely to be exfoliated or separated in relatively thick oxide films because of their dissimilar properties at vicinities close to the interface between the substrate and aluminum oxide thin films. Therefore, the thickness of the oxide film, and the amount of aluminum, are crucial for controlling the formation of aluminum oxide thin films with high resistivity in FeCo-V alloys.