ALLOY FORMATION OF ULTRATHIN Ni FILMS ON Al(111) SURFACE AT ROOM TEMPERATURE

Abstract

The growth characteristics of ultrathin Ni films deposited on Al(111) surfaces at room temperature have been studied using high energy ion scattering/channeling (HEIS), X-ray photoelectron spectroscopy (XPS) and low energy ion scattering (LEIS). Ion channeling results show that Ni atoms deposited on the Al(111) surface react with Al substrate atoms to form two different Ni–Al alloys between 0 and 5.5 ML of Ni coverage. Alloy phases of Ni 2 Al 3 up to 1.5 ML and NiAl up to 5.5 ML were determined by XPS peak analysis. At higher Ni coverage, LEIS and XPS spectra suggest that islands of Ni metal were formed on the surface. Diffusion of Ni into the Al substrate or segregation of Al to the surface was observed during the alloy formation. The Ni 2 Al 3 phase was apparently transformed into the NiAl phase by the additional Ni deposition, and the islands of Ni metal formed on the Al-rich surface of the NiAl alloy.