ARXPS and DFT studies of thermally induced Pb surface segregation on Au/Cu alloys

• Surface segregation of Pb impurities in AuCu alloys was studied by ARXPS and DFT.
• ARXPS show a 23% surface coverage by Pb atoms.
• DFT calculations predict a ¼ ML coverage of Pb atoms in the first atomic layer.
• The results show that bulk systems are affected while leaving nanoparticulate systems unaffected.

Surface segregation of Pb has been studied using angle resolved X-ray Photoelectron Spectroscopy (ARXPS) and Density Functional Theory (DFT) modelling in a polycrystalline Au0.85Cu0.15 alloy. Au surface enrichment was found in the alloy surface, whereas Pb surface enrichment was detected after annealing. ARXPS depth profiles show a 23% surface coverage by Pb atoms. DFT calculations predict an approximate coverage of ¼ monolayer (ML) of Pb atoms in the first atomic layer, consistent with the experimental results. The results presented here are an example of the importance of low concentration of impurities in determining the surface composition of bulk alloys.

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