Newly generated thick amorphous oxide layer at electrode/sol-gel film interface under strong external electric field

Abstract

SrTiO3/nano-Al2O3 composite films have been prepared using a sol-gel spin-coating method. When external electric fields were previously applied to the films with Al electrodes, the dielectric properties were strongly correlated with the applied field: both the dielectric constant and the dielectric loss decreased gradually with an increase in the previously applied voltage. For the films with Al electrodes, a superior dielectric strength of 507 MV/m was achieved; more importantly, the leakage current remained on the same order, i.e., microamperes; the results were ascribed to the Al electrode/film interface-reactions. The interface-reactions were experimentally confirmed by the cross-sectional transmission electron microscopy images and theoretically determined by Faraday's laws. The anodic oxidation reactions dominate the interface-reactions. The newly generated aluminum oxide originating from the interface-reactions contributes to the electric properties of the films.