Sputter etching studies of Fe–Ni and Fe–Pd films

Sputtering studies of Fe1−x–Nix (x=0.05 to 0.95) films were made and compared with those of Fe1−x–Pdx (x=0.06 to 0.7) films. Plots of steady-state AES and ESCA signal intensity ratios versus bulk composition ratios for the Fe–Pd system gave two straight lines intersecting near x=0.38, where a bcc to fcc phase transition occurs. Similar plots for the Fe–Ni system showed a single straight line across the whole composition range although a similar phase transition occurs at x∠0.4. Values of slopes obtained from normalized AES and ESCA data were similar for the Fe–Ni but differed by a factor of 3 for the Fe–Pd system. Since ESCA has a larger sampling depth than AES for both alloy systems, these differences are attributed to the presence of a significant altered layer on the sputtered Fe–Pd surface, which is absent on sputtered surfaces of Fe–Ni films. This result is compared to the different diffusion rates of these two systems: (1) Depth profiles for air-exposed and deliberately oxidized (160°–250 °C) films indicated that diffusion is much faster in the Fe–Ni than the Fe–Pd systems, and (2) direct measurement of interdiffusion in Fe–Ni and Fe–Pd couples demonstrated much faster interdiffusion in the Fe–Ni system.