Improving dielectric performance in anodic aluminum oxide via detection and passivation of defect states

The electronic and ionic transports in 32–56 nm thick anodic aluminum oxide films are investigated before and after a 1-h anneal at 200–400 °C in argon. Results are correlated to their defect density as measured by the Mott-Schottky technique. Solid state measurements show that electronic conduction upon annealing is hindered by an increase in the Schottky emission barrier, induced by a reduction in dopant density. Using an electrochemical contact, the films fail rapidly under cathodic polarization, unless defect density is decreased down to 1017 cm−3, resulting in a three order of magnitude reduction in current and no visible gas evolution. Under anodic polarization, the decrease in defect density delays the onset of ionic conduction as well as further oxide growth and failure.