Impedance of barrier-type oxide layer on aluminum

The impedance characteristics of barrier-type oxide layers on aluminum was studied using impedance spectroscopy. Since anodic films on Al have a varia ble stoichiometry with a gradual reduction of oxygen deficiency towards the oxide-electrolyte interface, the interpretation of impedance spectra for o xide layers is complex and the impedance of surface layers differs from tho se of ideal capacitors. This frequency response of the layer with conductan ce gradients cannot be described by a single resistance-capacitance (RC) el ement. The oxide layers of Al are properly described by the Young model of dielectric constant with a vertical decay of conductivity.