Composition and structure of enriched alloy layers in filmed Al alloys studied by medium-energy ion scattering

The topmost 20 nm of an electropolished Al–1 at.% Cu alloy has been investigated at sub-nanometre resolution using medium-energy ion scattering. Differences in the composition and depth of the enriched Cu layer are observed. Most significantly, the enriched layer contains regions of differing structure and/or lattice orientation with Cu atoms located in distinct ordered regions, consistent with the presence of Cu-rich clusters. Surface-segregated Si and Cu are observed and Cl and Cu are found in the oxide