Semiconductor aspects of the passive oxide film on aluminum as modified by surface alloying

Abstract For a series of binary aluminum surface alloys prepared by ion implantation, the critical pitting potential is a linear function of the isoelectric point of the oxide of the alloying element in the binary alloy. This follows by first showing that the critical pitting potential is a linear function of the flat-band potential of the oxide-covered surface. The flat-band potential is shown to be a linear function of the isoelectric point of the oxide film on the alloy surface. Use is then made of the mixing rule to relate the isoelectric point of the mixed oxide on the binary alloy to the isoelectric point of its constituent oxides (the oxide of the alloying element plus Al2O3). For a series of ion-implanted binary aluminum surface alloys, there is good agreement between the predicted and experimental pitting potentials, given the simplifying assumptions that have been made.