Electronic Defects and Interface Potentials for A1 Oxide Films on A1 and Their Relationship to Electrochemical Properties

摘要

The relative electronic defect densities and oxide interface potentials were determined for naturally-occurring and synthetic A1 oxides on A1. In addition, the effect of electrochemical treatment on the oxide electrical properties was assessed. The measurements revealed (1) that the open circuit potential of A1 in aqueous solution is inversely correlated with the oxide electronic defect density (viz., lower oxide conductivities are correlated with higher open circuit potentials), and (2) the electronic defect density within the A1 oxide is increased upon exposure to an aqueous electrolyte at open circuit or applied cathodic potentials, while the electronic defect density is reduced upon exposure to slight anodic potentials in solution. This last result, combined with recent theoretical predictions, suggests that hydrogen may be associated with electronic defects within the A1 oxide, and that this H may be a mobile species, diffusing as H(sup +). The potential drop across the oxide layer when immersed in solution at open circuit conditions was also estimated and found to be 0.3 V, with the field direction attracting positive charge towards the A1/oxide interface.