(324f) Composition Spread Alloy Films for High Throughput Study of Surface Segregation

The surface composition of a multi-component material is not the same as its bulk due to preferential segregation of some components to the surface. Segregation arises from the need of the surface to minimize its free energy. Segregation influences processes that depend on the surface properties of alloys such as catalysis, corrosion, and tribology; it is a complex function of bulk composition and environmental factors such as temperature, and the presence of adsorbed species. However, because alloy composition varies continuously, the comprehensive study of segregation over all possible alloy compositions requires development of accelerated research tools.

To enable rapid study of segregation throughout a complex, multidimensional composition space, we have developed a novel offset filament deposition source for preparation of Composition Spread Alloy Films (CSAFs), which contain all possible alloy compositions on a single substrate. In this work, we illustrate the performance of the deposition source for preparation of Pd_xCu_100-x CSAFs. We apply Low Energy Ion Scattering Spectroscopy (LEISS) and X-ray Photoelectron Spectroscopy (XPS) for spatially resolved characterization of the top surface and near surface (~ 7 atom layers) composition of the Pd_xCu_100-x CSAFs. We examine segregation patterns as functions of bulk composition, anneal temperature and adsorbed sulfur and compare the CSAF results with those from a single composition Pd₇₀Cu₃₀ alloy.