Characterization of the oxide/hydroxide surface of aluminium using x-ray photoelectron spectroscopy: a procedure for curve fitting the O 1s core level

The performance of coated and bonded aluminium relies heavily upon its surf ace chemistry and hence characterization of the aluminium surface is import ant. A method to quantify the hydroxide concentration at aluminium oxide/hy droxide surfaces by curve fitting the O Is peak is developed and tested in this paper. Pseudoboehmite, AlO(OH), is formed at the surface of aluminium after immers ion in boiling water. The surface of this material was used to determine th e binding energy of the unresolved O Is component peaks that were reference d to the binding energy of the Al 2p oxide component. III vacuo heating res ulted in changes in the elemental and functional composition that were cons istent with dehydration of the pseudoboehmite, It is proposed that the resu ltant film comprises gamma-alumina with residual hydroxide groups. The O Is curve-fitting method was applied to air-formed films with known at mospheric exposure histories before and after healing in vacuo. The change in both the elemental composition and functional stoichiometry of the films upon heating was consistent with significant but incomplete dehydration. T he probable surface phases are determined from the functional and elemental composition. Copyright O 2000 John Wiley & Sons, Ltd.