Study on oxidation of Gd film grown on Ni (110) surface by synchrotron radiation photoemission

Soft X-ray synchrotron radiation photoemission and X-ray photoelectron spectroscopy(XPS) were used to study the interaction of oxygen with Gd overlayers grown in situ. on Ni(110) surface and with the Gd-Ni composite film. Oxygen showed a large primary sticking coefficient on a 3.7 nm-thick Gd film. The high binding energy(BE) peak in the double-peak of Gd 4f emission attenuated with the increase of oxygen exposure and almost disappeared when the specimen was annealed at 800 K after a 50 L coverage. The O 1s XPS spectra exhibited only one peak attributed to lattice oxygen at 529.6 eV in the range of 0-50 L exposure. Over the surface of composite film prepared by slight oxidation and high temperature (1000 K) annealing treatment of 0.63 nm Gd film, the adsorption of oxygen resulted in the surface segregation and oxidation of Gd component. Two kinds of oxygen species, the chemisorbed O- ion and lattice oxygen, were detected. The oxidation mechanism of Gd film as well as the nature and evolution of the surface oxygen species are discussed.