(18h) Surface Segregation across Ternary Alloy Composition Space

Surface segregation is a phenomenon common to all multicomponent materials and one that plays a critical role in determining their surface properties. Comprehensive studies of surface segregation versus bulk composition in ternary alloys have been prohibitive because of the need to study many different compositions. In this work, high-throughput low-energy He⁺ ion scattering spectra (LEIS) and energy dispersive X-ray spectra (EDX) were collected from a Cu_xAu_yPd_1-x-y composition spread alloy film (CSAF) under ultra-high vacuum conditions. These have been used to quantify surface segregation across the entire Cu_xAu_yPd_1-x-ycomposition space (x=0 -> 1 and y=0 -> 1-x).

Surface compositions at 164 different bulk compositions were measured, with results consistent with existing literature on binary alloy segregation, while additional findings indicate that LEIS may be used to distinguish between surface structures with different surface atom densities in high-throughput experiments. An extended Langmuir-MacLean model, which describes ternary alloy segregation, has been used to analyze experimental data from the ternary alloys and to estimate pair-wise segregation free energies and segregation equilibrium constants. The ability to study surface segregation across ternary alloy composition space with high throughput methods has been validated, and the impact of bulk alloy phase on surface segregation is demonstrated and discussed.