Quantification of oxide film thickness at the surface of aluminium using XPS

Oxide films grown anodically at the surface of superpure aluminium are used as standards to assess the accuracy of the thickness ( d XPS ) determined using the Beer–Lambert treatment of the Al 2p metal and oxide peak intensities. For the fitting conditions employed, the value of d XPS is found to be very close to the true film thickness for films <10 nm thick, beyond which imprecise values are obtained. A surface layer of hydration is identified from the curve fitting of the O 1s core level, which would qualitatively account for the slight underestimate of film thickness provided by the expression for d XPS . The validity of the Al 2p fit may be determined through this correlation of thickness but requires first a quantitative assessment of the thickness and composition of the hydroxide‐rich layer.