Interface states at the anodized Al2O3-metal interface

Abstract

The capacitance of Al–Al 2 O 3 -metal capacitors with Al 2 O 3 of different thicknesses, formed by anodizing evaporated Al films in ethylene glycol-based or H 2 O -based electrolytes to different voltages, has been measured between 10 kHz and 1 MHz for ten metal electrodes. The linear dependence of inverse capacitance on anodizing voltage, and thus on Al 2 O 3 thickness, shows that there is an interface capacitance in series with the bulk capacitance due to the dielectric properties of anodized Al 2 O 3 . The interface capacitance, C I , is not a characteristic of the Al 2 O 3 -metal combination; it depends on the vacuum deposition conditions for the metal electrodes. C I is associated with interface states at the Al 2 O 3 -metal interface, not with field penetration into metal electrodes.