Surface properties and electronic structure of amorphous Zr/sub 75/Ni/sub 25/ and Zr/sub 75/Ni/sub 25/ hydride studied by photoemission

We have studied the surface composition of melt-spun amorphous Zr/sub 75/Ni/sub 25/ ribbons by means of x-ray-photoelectron-spectroscopic core-level analysis and depth profiling and the electronic structure of carefully cleaned Zr/sub 75/Ni/sub 25/ and of Zr/sub 75/Ni/sub 25/ hydride by means of valence-band and core-level analysis. We observed strong oxygen-induced segregation in a surface layer on both sides of the ribbons. On ribbons which were kept in air for three years the surface layer is much thicker (≅60 nm) on the dark (wheel) side, suggesting enhanced corrosion. In contrast, we see no significant segregation due to hydrogen adsorption or absorption, but the appearance of the hydrogen-induced bonding band centered at 6.5 eV below E/sub F/, a shift by 0.6 eV of the Zr 3d line, and a weak loss of asymmetry of the Ni 2p line upon hydride formation. We conclude that neither the oxygen- or hydrogen-induced segregation effects nor the electronic structure of amorphous Zr/sub 75/Ni/sub 25/ and Zr/sub 75/Ni/sub 25/ hydride differ radically from those of corresponding crystalline alloys