The surface-segregation of Cu was investigated in electrodeposited Ni–Fe layers by using X-ray photo-electron spectroscopy, Auger electron spectroscopy, secondary-ion mass spectroscopy and atomic force microscopy. The results indicated that Cu segregation and accumulation took place in areated and de-areated baths and the amount of segregated Cu increased after air exposure. This phenomenon was explained by the lower interfacial tension of Cu in comparison with Ni and Fe. The results revealed more surface segregation in the electrodeposit than reported for a vacuum. This was attributed to interface charging and higher surface diffusion under an applied potential. The effect of interface charging upon the interfacial tension was explained in terms of the Lippmann equation. An increasing Cu accumulation after air exposure was attributed to selective oxidation in alloys and a higher tendency of Cu to surface oxidation.

Diffusion and Segregation of Substrate Copper in Electrodeposited Ni–Fe Thin Films. M.M.Ahadian, A.Irajizad, E.Nouri, M.Ranjbar, A.Dolati: Journal of Alloys and Compounds, 2007, 443[1-2], 81-6