Alloy compositional profiles by AES, ESCA, and ion sputtering: Air-exposed Fe1−xPdx films

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Abstract
Surface studies of air-exposed, 1000 Å-thick Fe1−xPdx alloy films with x=0.06–0.74 were carried out using AES, ESCA, and in situ ion sputtering techniques. It was found that Fe is preferentially oxidized on the surface with a Pd-enriched region formed underneath the oxide layer. The iron oxide thickness decreases linearly as the Pd concentration is increased, becoming quite small for x≳0.6. Fe2O3 is the dominant oxidation product for the lower Pd concentration alloys while Fe3O4 appears to be the major oxide for x≳0.36. The steady state composition of the surfaces measured both by AES and ESCA techniques afer prolonged sputtering also indicated that the relative Pd-to-Fe sputtering yield remains constant for films with x between 0.06 and ∠0.38 and decreases to another constant value for films with larger x values. No preferential sputtering is observed in the AES case for alloys with x≳0.38, if the atomic density is taken into account; for x<0.38, Pd sputters about twice as fast as Fe. In the ESCA case, very strong preferential sputtering of Pd to Fe is observed. Possible origins for this sputtering yield change, including the phase transition and the residual oxygen content of the alloy, are discussed.

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