Quantitative AES analysis of coevaporated Cu/Ni films and the effects of ion sputtering on them: experiments at liquid nitrogen and room temperature

Abstract

Samples of various concentrations were made by coevaporation of Cu and Ni. The coevaporation was carried out by simultaneous controlled electron bombardment heating of independent evaporation sources. The Auger-electron spectroscopy (AES) measurements were made by using a CMA and could be done following coevaporation or ion sputtering without moving the sample in the UHV system. The absolute composition of the sample was measured by atomic absorption spectroscopy (AAS). A linear relation was found between the AES measurements (700–1000 eV) and the results of AAS when the coevaporation was made onto the substrate at almost liquid nitrogen temperature. It should be mentioned that samples of homogeneous concentration from the surface to the bulk could be obtained, making quantitative AES possible. On the other hand, coevaporation onto substrates at room temperature resulted in Cu-rich surfaces being obtained. Quantitative AES analysis using lower-energy Auger peaks (80–120 eV) was also made using the same samples and results similar to those calculated from the higher-energy Auger transitions (700–1000 eV) were obtained. Samples coevaporated near liquid nitrogen temperature were sputtered by argon ions of 500–2000 eV and no significant difference was observed between sputtering near liquid nitrogen temperature or after allowing the sample to warm to room temperature. The surface of a 60 at. % Cu film became Ni-rich by 4, 8, and 12 at. % for ion energies of 500, 1000, and 2000 eV, respectively.