The effects of elevated temperature on sputter depth profiles of silver/nickel bilayers

The effect of elevated temperature on the sputtering behavior of silver/nickel bilayers was studied using Auger electron spectroscopy and argon ion sputtering while specimens were held at elevated temperatures (25, 135, 235, 335, and 435 °C). We find that the silver overlayer tranforms from a layer to islands during ion sputtering at temperatures above 100 °C. The transformation to islands is thought to relieve film stresses caused by film-growth and/or lattice mismatch. Surface diffusion of silver is also observed at elevated temperature (> 100 °C), This causes the lower surface energy metal (Ag) to cover the higher surface energy metal (Ni) in regions between the islands. These experiments show that properties of the system such as the heat of mixing, and the surface and interface energies need to be considered when the sputter depth profiling technique is used to study thin film structures, particularly when sputtering is performed at elevated temperatures.