Preferential sputtering and surface segregation of CuZr alloys

The changes included in the surface composition of a Cu-Zr (50 at%) alloy by Ar+ ion bombardment has been studied using ion scattering spectroscopy (ISS), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). ISS results indicate that the outermost atomic layer is Zr-rich, comprising85 ± 5%, whereas AES and XPS gives that the subsurface is also Zr-rich, comprising70 ± 3%. These results suggest that the Ar+ ion bombardment induces an altered layer in depth in which Zr concentration approach exponentially to the bulk concentration with a quite large decay length. This phenomenon is quite different compared to other alloys having a concentration dip occurring in the uppermost atomic layer. The results of elevated temperature experiment clearly shows that Zr atoms are thermally segregating to the uppermost atomic layers. The Zr-rich in the uppermost atomic layer can be explained in terms of preferential sputtering and radiation induced surface segregation effects.